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DATA SHEET Product data sheet Supersedes data of 1999 Apr 15 2004 Jan 21 DISCRETE SEMICONDUCTORS PMBT4403 PNP switching transistor dbook, halfpage M3D088 2004 Jan 21 2 NXP Semiconductors Product data sheet PNP switching transistor PMBT4403 FEATURES •High current (max. 600 mA) •Low voltage (max. 40 V). APPLICATIONS •Industrial and consumer switching applications. DESCRIPTION PNP switching transistor in a SOT23 plastic package. NPN complement: PMBT4401. MARKING Note 1.* = p : Made in Hong Kong. * = t : Made in Malaysia. * = W : Made in China. PINNING TYPE NUMBER MARKING CODE(1) PMBT4403 *2T PIN DESCRIPTION 1 base 2 emitter 3 collector Fig.1 Simplified outline (SOT23) and symbol.handbook, halfpage213MAM256Top view231 ORDERING INFORMATION LIMITING VALUES In accordance with the Absolute Maximum Rating System (IEC 60134). Note 1.Transistor mounted on an FR4 printed-circuit board. TYPE NUMBER PACKAGE NAME DESCRIPTION VERSION PMBT4403 − plastic surface mounted package; 3 leads SOT23 SYMBOL PARAMETER CONDITIONS MIN. MAX. UNIT VCBO collector-base voltage open emitter − −40 V VCEO collector-emitter voltage open base − −40 V VEBO emitter-base voltage open collector − −5 V IC collector current (DC) − −600 mA ICM peak collector current − −800 mA IBM peak base current − −200 mA Ptot total power dissipation Tamb ≤ 25 °C; note 1 − 250 mW Tstg storage temperature −65 +150 °C Tj junction temperature − 150 °C Tamb operating ambient temperature −65 +150 °C 2004 Jan 21 3 NXP Semiconductors Product data sheet PNP switching transistor PMBT4403 THERMAL CHARACTERISTICS Note 1.Transistor mounted on an FR4 printed-circuit board. CHARACTERISTICS Tamb = 25 °C unless otherwise specified. SYMBOL PARAMETER CONDITIONS VALUE UNIT Rth(j-a) thermal resistance from junction to ambient note 1 500 K/W SYMBOL PARAMETER CONDITIONS MIN. MAX. UNIT ICBO collector-base cut-off current IE = 0; VCB = −40 V − −50 nA IEBO emitter-base cut-off current IC = 0; VEB = −5 V − −50 nA hFE DC current gain VCE = −1 V; (see Fig.2) IC = −0.1 mA 30 − IC = −1 mA 60 − IC = −10 mA 100 − VCE = −2 V IC = −150 mA 100 300 IC = −500 mA 20 − VCEsat collector-emitter saturation voltage IC = −150 mA; IB = −15 mA − −400 mV IC = −500 mA; IB = −50 mA − −750 mV VBEsat base-emitter saturation voltage IC = −150 mA; IB = −15 mA − −950 mV IC = −500 mA; IB = −50 mA − −1.3 V Cc collector capacitance IE = Ie = 0; VCB = −10 V; f = 1 MHz − 8.5 pF Ce emitter capacitance IC = Ic = 0; VEB = −500 mV; f = 1 MHz − 35 pF fT transition frequency IC = −20 mA; VCE = −10 V; f = 100 MHz 200 − MHz Switching times (between 10% and 90% levels); (see Fig.3) ton turn-on time ICon = −150 mA; IBon = −15 mA; IBoff = 15 mA − 40 ns td delay time − 15 ns tr rise time − 30 ns toff turn-off time − 350 ns ts storage time − 300 ns tf fall time − 50 ns 2004 Jan 21 4 NXP Semiconductors Product data sheet PNP switching transistor PMBT4403 Fig.2 DC current gain; typical values.ndbook, full pagewidth0300100200MGD812−10−1−1−10−102−103hFEIC mAVCE = −1 V Fig.3 Test circuit for switching times.handbook, full pagewidthRCR2R1DUTMGD624VoRB(probe)450 Ω(probe)450 ΩoscilloscopeoscilloscopeVBBViVCCVi = −9.5 V; T = 500 μs; tp = 10 μs; tr = tf ≤ 3 ns.R1 = 68 Ω; R2 = 325 Ω; RB = 325 Ω; RC = 160 Ω.VBB = 3.5 V; VCC = −29.5 V.Oscilloscope: input impedance Zi = 50 Ω. 2004 Jan 21 5 NXP Semiconductors Product data sheet PNP switching transistor PMBT4403 PACKAGE OUTLINEUNITA1max.bpcDE e1HELpQwv REFERENCESOUTLINEVERSIONEUROPEANPROJECTIONISSUE DATE04-11-0406-03-16 IEC JEDEC JEITAmm0.10.480.380.150.093.02.81.41.20.95e1.92.52.10.550.450.10.2DIMENSIONS (mm are the original dimensions)0.450.15 SOT23TO-236ABbpDe1eAA1LpQdetail XHEEwMvMABAB012 mmscaleA1.10.9cX123Plastic surface-mounted package; 3 leadsSOT23 2004 Jan 21 6 NXP Semiconductors Product data sheet PNP switching transistor PMBT4403 DATA SHEET STATUS Notes 1.Please consult the most recently issued document before initiating or completing a design. 2.The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com. DOCUMENTSTATUS(1) PRODUCT STATUS(2) DEFINITION Objective data sheet Development This document contains data from the objective specification for product development. Preliminary data sheet Qualification This document contains data from the preliminary specification. Product data sheet Production This document contains the product specification. DISCLAIMERS General ⎯ Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes ⎯ NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. 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The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified. © 2009 Microchip Technology Inc. DS39632E-page 1 PIC18F2455/2550/4455/4550 Universal Serial Bus Features: • USB V2.0 Compliant • Low Speed (1.5 Mb/s) and Full Speed (12 Mb/s) • Supports Control, Interrupt, Isochronous and Bulk Transfers • Supports up to 32 Endpoints (16 bidirectional) • 1 Kbyte Dual Access RAM for USB • On-Chip USB Transceiver with On-Chip Voltage Regulator • Interface for Off-Chip USB Transceiver • Streaming Parallel Port (SPP) for USB streaming transfers (40/44-pin devices only) Power-Managed Modes: • Run: CPU on, Peripherals on • Idle: CPU off, Peripherals on • Sleep: CPU off, Peripherals off • Idle mode Currents Down to 5.8 μA Typical • Sleep mode Currents Down to 0.1 μA Typical • Timer1 Oscillator: 1.1 μA Typical, 32 kHz, 2V • Watchdog Timer: 2.1 μA Typical • Two-Speed Oscillator Start-up Flexible Oscillator Structure: • Four Crystal modes, including High-Precision PLL for USB • Two External Clock modes, Up to 48 MHz • Internal Oscillator Block: - 8 user-selectable frequencies, from 31 kHz to 8 MHz - User-tunable to compensate for frequency drift • Secondary Oscillator using Timer1 @ 32 kHz • Dual Oscillator Options allow Microcontroller and USB module to Run at Different Clock Speeds • Fail-Safe Clock Monitor: - Allows for safe shutdown if any clock stops Peripheral Highlights: • High-Current Sink/Source: 25 mA/25 mA • Three External Interrupts • Four Timer modules (Timer0 to Timer3) • Up to 2 Capture/Compare/PWM (CCP) modules: - Capture is 16-bit, max. resolution 5.2 ns (TCY/16) - Compare is 16-bit, max. resolution 83.3 ns (TCY) - PWM output: PWM resolution is 1 to 10-bit • Enhanced Capture/Compare/PWM (ECCP) module: - Multiple output modes - Selectable polarity - Programmable dead time - Auto-shutdown and auto-restart • Enhanced USART module: - LIN bus support • Master Synchronous Serial Port (MSSP) module Supporting 3-Wire SPI (all 4 modes) and I2C™ Master and Slave modes • 10-Bit, Up to 13-Channel Analog-to-Digital Converter (A/D) module with Programmable Acquisition Time • Dual Analog Comparators with Input Multiplexing Special Microcontroller Features: • C Compiler Optimized Architecture with Optional Extended Instruction Set • 100,000 Erase/Write Cycle Enhanced Flash Program Memory Typical • 1,000,000 Erase/Write Cycle Data EEPROM Memory Typical • Flash/Data EEPROM Retention: > 40 Years • Self-Programmable under Software Control • Priority Levels for Interrupts • 8 x 8 Single-Cycle Hardware Multiplier • Extended Watchdog Timer (WDT): - Programmable period from 41 ms to 131s • Programmable Code Protection • Single-Supply 5V In-Circuit Serial Programming™ (ICSP™) via Two Pins • In-Circuit Debug (ICD) via Two Pins • Optional Dedicated ICD/ICSP Port (44-pin, TQFP package only) • Wide Operating Voltage Range (2.0V to 5.5V) Device Program Memory Data Memory I/O 10-Bit A/D (ch) CCP/ECCP (PWM) SPP MSSP EUSART Comparators Timers Flash 8/16-Bit (bytes) # Single-Word Instructions SRAM (bytes) EEPROM (bytes) SPI Master I2C™ PIC18F2455 24K 12288 2048 256 24 10 2/0 No Y Y 1 2 1/3 PIC18F2550 32K 16384 2048 256 24 10 2/0 No Y Y 1 2 1/3 PIC18F4455 24K 12288 2048 256 35 13 1/1 Yes Y Y 1 2 1/3 PIC18F4550 32K 16384 2048 256 35 13 1/1 Yes Y Y 1 2 1/3 28/40/44-Pin, High-Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology PIC18F2455/2550/4455/4550 DS39632E-page 2 © 2009 Microchip Technology Inc. Pin Diagrams 40-Pin PDIP PIC18F2455 28-Pin PDIP, SOIC PIC18F2550 10 11 2 345 6 1 8 7 9 12 13 14 15 16 17 18 19 20 23 24 25 26 27 28 22 21 MCLR/VPP/RE3 RA0/AN0 RA1/AN1 RA2/AN2/VREF-/CVREF RA3/AN3/VREF+ RA4/T0CKI/C1OUT/RCV RA5/AN4/SS/HLVDIN/C2OUT VSS OSC1/CLKI OSC2/CLKO/RA6 RC0/T1OSO/T13CKI RC1/T1OSI/CCP2(1)/UOE RC2/CCP1 VUSB RB7/KBI3/PGD RB6/KBI2/PGC RB5/KBI1/PGM RB4/AN11/KBI0 RB3/AN9/CCP2(1)/VPO RB2/AN8/INT2/VMO RB1/AN10/INT1/SCK/SCL RB0/AN12/INT0/FLT0/SDI/SDA VDD VSS RC7/RX/DT/SDO RC6/TX/CK RC5/D+/VP RC4/D-/VM RB7/KBI3/PGD RB6/KBI2/PGC RB5/KBI1/PGM RB4/AN11/KBI0/CSSPP RB3/AN9/CCP2(1)/VPO RB2/AN8/INT2/VMO RB1/AN10/INT1/SCK/SCL RB0/AN12/INT0/FLT0/SDI/SDA VDD VSS RD7/SPP7/P1D RD6/SPP6/P1C RD5/SPP5/P1B RD4/SPP4 RC7/RX/DT/SDO RC6/TX/CK RC5/D+/VP RC4/D-/VM RD3/SPP3 RD2/SPP2 MCLR/VPP/RE3 RA0/AN0 RA1/AN1 RA2/AN2/VREF-/CVREF RA3/AN3/VREF+ RA4/T0CKI/C1OUT/RCV RA5/AN4/SS/HLVDIN/C2OUT RE0/AN5/CK1SPP RE1/AN6/CK2SPP RE2/AN7/OESPP VDD VSS OSC1/CLKI OSC2/CLKO/RA6 RC0/T1OSO/T13CKI RC1/T1OSI/CCP2(1)/UOE RC2/CCP1/P1A VUSB RD0/SPP0 RD1/SPP1 12 34 56789 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 PIC18F4455 PIC18F4550 Note 1: RB3 is the alternate pin for CCP2 multiplexing. © 2009 Microchip Technology Inc. DS39632E-page 3 PIC18F2455/2550/4455/4550 Pin Diagrams (Continued) PIC18F4455 44-Pin TQFP 44-Pin QFN PIC18F4455 PIC18F4550 PIC18F4550 10 11 23 6 1 18 19 20 21 22 12 13 14 15 38 8 7 44 43 42 41 40 39 16 17 29 30 31 32 33 23 24 25 26 27 28 36 34 35 9 37 RA3/AN3/VREF+ RA2/AN2/VREF-/CVREF RA1/AN1 RA0/AN0 MCLR/VPP/RE3 NC/ICCK(2)/ICPGC(2) RB7/KBI3/PGD RB6/KBI2/PGC RB5/KBI1/PGM RB4/AN11/KBI0/CSSPP NC/ICDT(2)/ICPGD(2) RC6/TX/CK RC5/D+/VP RC4/D-/VM RD3/SPP3 RD2/SPP2 RD1/SPP1 RD0/SPP0 VUSB RC2/CCP1/P1A RC1/T1OSI/CCP2(1)/UOE NC/ICPORTS(2) NC/ICRST(2)/ICVPP(2) RC0/T1OSO/T13CKI OSC2/CLKO/RA6 OSC1/CLKI VSS VDD RE2/AN7/OESPP RE1/AN6/CK2SPP RE0/AN5/CK1SPP RA5/AN4/SS/HLVDIN/C2OUT RA4/T0CKI/C1OUT/RCV RC7/RX/DT/SDO RD4/SPP4 RD5/SPP5/P1B RD6/SPP6/P1C VSS VDD RB0/AN12/INT0/FLT0/SDI/SDA RB1/AN10/INT1/SCK/SCL RB2/AN8/INT2/VMO RB3/AN9/CCP2(1)/VPO RD7/SPP7/P1D 5 4 10 11 23 6 1 18 19 20 21 22 12 13 14 15 38 8 7 44 43 42 41 40 39 16 17 29 30 31 32 33 23 24 25 26 27 28 36 34 35 9 37 RA3/AN3/VREF+ RA2/AN2/VREF-/CVREF RA1/AN1 RA0/AN0 MCLR/VPP/RE3 RB7/KBI3/PGD RB6/KBI2/PGC RB5/KBI1/PGM RB4/AN11/KBI0/CSSPP NC RC6/TX/CK RC5/D+/VP RC4/D-/VM RD3/SPP3 RD2/SPP2 RD1/SPP1 RD0/SPP0 VUSB RC2/CCP1/P1A RC1/T1OSI/CCP2(1)/UOE RC0/T1OSO/T13CKI OSC2/CLKO/RA6 OSC1/CLKI VSS VDD RE2/AN7/OESPP RE1/AN6/CK2SPP RE0/AN5/CK1SPP RA5/AN4/SS/HLVDIN/C2OUT RA4/T0CKI/C1OUT/RCV RC7/RX/DT/SDO RD4/SPP4 RD5/SPP5/P1B RD6/SPP6/P1C VSS VDD RB0/AN12/INT0/FLT0/SDI/SDA RB1/AN10/INT1/SCK/SCL RB2/AN8/INT2/VMO RB3/AN9/CCP2(1)/VPO RD7/SPP7/P1D 5 4 VSS VDD VDD Note 1: RB3 is the alternate pin for CCP2 multiplexing. 2: Special ICPORT features available in select circumstances. See Section 25.9 “Special ICPORT Features (44-Pin TQFP Package Only)” for more information. PIC18F2455/2550/4455/4550 DS39632E-page 4 © 2009 Microchip Technology Inc. Table of Contents 1.0 Device Overview .......................................................................................................................................................................... 7 2.0 Oscillator Configurations ............................................................................................................................................................ 23 3.0 Power-Managed Modes ............................................................................................................................................................. 35 4.0 Reset .......................................................................................................................................................................................... 45 5.0 Memory Organization ................................................................................................................................................................. 59 6.0 Flash Program Memory.............................................................................................................................................................. 81 7.0 Data EEPROM Memory ............................................................................................................................................................. 91 8.0 8 x 8 Hardware Multiplier............................................................................................................................................................ 97 9.0 Interrupts .................................................................................................................................................................................... 99 10.0 I/O Ports ................................................................................................................................................................................... 113 11.0 Timer0 Module ......................................................................................................................................................................... 127 12.0 Timer1 Module ......................................................................................................................................................................... 131 13.0 Timer2 Module ......................................................................................................................................................................... 137 14.0 Timer3 Module ......................................................................................................................................................................... 139 15.0 Capture/Compare/PWM (CCP) Modules ................................................................................................................................. 143 16.0 Enhanced Capture/Compare/PWM (ECCP) Module................................................................................................................ 151 17.0 Universal Serial Bus (USB) ...................................................................................................................................................... 165 18.0 Streaming Parallel Port ............................................................................................................................................................ 191 19.0 Master Synchronous Serial Port (MSSP) Module .................................................................................................................... 197 20.0 Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) ............................................................... 243 21.0 10-Bit Analog-to-Digital Converter (A/D) Module ..................................................................................................................... 265 22.0 Comparator Module.................................................................................................................................................................. 275 23.0 Comparator Voltage Reference Module................................................................................................................................... 281 24.0 High/Low-Voltage Detect (HLVD)............................................................................................................................................. 285 25.0 Special Features of the CPU.................................................................................................................................................... 291 26.0 Instruction Set Summary .......................................................................................................................................................... 313 27.0 Development Support............................................................................................................................................................... 363 28.0 Electrical Characteristics .......................................................................................................................................................... 367 29.0 DC and AC Characteristics Graphs and Tables....................................................................................................................... 407 30.0 Packaging Information.............................................................................................................................................................. 409 Appendix A: Revision History............................................................................................................................................................. 419 Appendix B: Device Differences......................................................................................................................................................... 419 Appendix C: Conversion Considerations ........................................................................................................................................... 420 Appendix D: Migration From Baseline to Enhanced Devices............................................................................................................. 420 Appendix E: Migration From Mid-Range to Enhanced Devices ......................................................................................................... 421 Appendix F: Migration From High-End to Enhanced Devices............................................................................................................ 421 Index .................................................................................................................................................................................................. 423 The Microchip Web Site ..................................................................................................................................................................... 433 Customer Change Notification Service .............................................................................................................................................. 433 Customer Support .............................................................................................................................................................................. 433 Reader Response .............................................................................................................................................................................. 434 PIC18F2455/2550/4455/4550 Product Identification System ............................................................................................................ 435 © 2009 Microchip Technology Inc. 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PIC18F2455/2550/4455/4550 DS39632E-page 6 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 7 PIC18F2455/2550/4455/4550 1.0 DEVICE OVERVIEW This document contains device-specific information for the following devices: This family of devices offers the advantages of all PIC18 microcontrollers – namely, high computational performance at an economical price – with the addition of high-endurance, Enhanced Flash program memory. In addition to these features, the PIC18F2455/2550/4455/4550 family introduces design enhancements that make these microcontrollers a logical choice for many high-performance, power sensitive applications. 1.1 New Core Features 1.1.1 nanoWatt TECHNOLOGY All of the devices in the PIC18F2455/2550/4455/4550 family incorporate a range of features that can significantly reduce power consumption during operation. Key items include: • Alternate Run Modes: By clocking the controller from the Timer1 source or the internal oscillator block, power consumption during code execution can be reduced by as much as 90%. • Multiple Idle Modes: The controller can also run with its CPU core disabled but the peripherals still active. In these states, power consumption can be reduced even further, to as little as 4%, of normal operation requirements. • On-the-Fly Mode Switching: The power-managed modes are invoked by user code during operation, allowing the user to incorporate power-saving ideas into their application’s software design. • Low Consumption in Key Modules: The power requirements for both Timer1 and the Watchdog Timer are minimized. See Section 28.0 “Electrical Characteristics” for values. 1.1.2 UNIVERSAL SERIAL BUS (USB) Devices in the PIC18F2455/2550/4455/4550 family incorporate a fully featured Universal Serial Bus communications module that is compliant with the USB Specification Revision 2.0. The module supports both low-speed and full-speed communication for all supported data transfer types. It also incorporates its own on-chip transceiver and 3.3V regulator and supports the use of external transceivers and voltage regulators. 1.1.3 MULTIPLE OSCILLATOR OPTIONS AND FEATURES All of the devices in the PIC18F2455/2550/4455/4550 family offer twelve different oscillator options, allowing users a wide range of choices in developing application hardware. These include: • Four Crystal modes using crystals or ceramic resonators. • Four External Clock modes, offering the option of using two pins (oscillator input and a divide-by-4 clock output) or one pin (oscillator input, with the second pin reassigned as general I/O). • An internal oscillator block which provides an 8 MHz clock (±2% accuracy) and an INTRC source (approximately 31 kHz, stable over temperature and VDD), as well as a range of 6 user-selectable clock frequencies, between 125 kHz to 4 MHz, for a total of 8 clock frequencies. This option frees an oscillator pin for use as an additional general purpose I/O. • A Phase Lock Loop (PLL) frequency multiplier, available to both the High-Speed Crystal and External Oscillator modes, which allows a wide range of clock speeds from 4 MHz to 48 MHz. • Asynchronous dual clock operation, allowing the USB module to run from a high-frequency oscillator while the rest of the microcontroller is clocked from an internal low-power oscillator. Besides its availability as a clock source, the internal oscillator block provides a stable reference source that gives the family additional features for robust operation: • Fail-Safe Clock Monitor: This option constantly monitors the main clock source against a reference signal provided by the internal oscillator. If a clock failure occurs, the controller is switched to the internal oscillator block, allowing for continued low-speed operation or a safe application shutdown. • Two-Speed Start-up: This option allows the internal oscillator to serve as the clock source from Power-on Reset, or wake-up from Sleep mode, until the primary clock source is available. • PIC18F2455 • PIC18LF2455 • PIC18F2550 • PIC18LF2550 • PIC18F4455 • PIC18LF4455 • PIC18F4550 • PIC18LF4550 PIC18F2455/2550/4455/4550 DS39632E-page 8 © 2009 Microchip Technology Inc. 1.2 Other Special Features • Memory Endurance: The Enhanced Flash cells for both program memory and data EEPROM are rated to last for many thousands of erase/write cycles – up to 100,000 for program memory and 1,000,000 for EEPROM. Data retention without refresh is conservatively estimated to be greater than 40 years. • Self-Programmability: These devices can write to their own program memory spaces under internal software control. By using a bootloader routine, located in the protected Boot Block at the top of program memory, it becomes possible to create an application that can update itself in the field. • Extended Instruction Set: The PIC18F2455/2550/4455/4550 family introduces an optional extension to the PIC18 instruction set, which adds 8 new instructions and an Indexed Literal Offset Addressing mode. This extension, enabled as a device configuration option, has been specifically designed to optimize re-entrant application code originally developed in high-level languages such as C. • Enhanced CCP Module: In PWM mode, this module provides 1, 2 or 4 modulated outputs for controlling half-bridge and full-bridge drivers. Other features include auto-shutdown for disabling PWM outputs on interrupt or other select conditions, and auto-restart to reactivate outputs once the condition has cleared. • Enhanced Addressable USART: This serial communication module is capable of standard RS-232 operation and provides support for the LIN bus protocol. The TX/CK and RX/DT signals can be inverted, eliminating the need for inverting buffers. Other enhancements include Automatic Baud Rate Detection and a 16-bit Baud Rate Generator for improved resolution. When the microcontroller is using the internal oscillator block, the EUSART provides stable operation for applications that talk to the outside world without using an external crystal (or its accompanying power requirement). • 10-Bit A/D Converter: This module incorporates programmable acquisition time, allowing for a channel to be selected and a conversion to be initiated, without waiting for a sampling period and thus, reducing code overhead. • Dedicated ICD/ICSP Port: These devices introduce the use of debugger and programming pins that are not multiplexed with other microcontroller features. Offered as an option in select packages, this feature allows users to develop I/O intensive applications while retaining the ability to program and debug in the circuit. 1.3 Details on Individual Family Members Devices in the PIC18F2455/2550/4455/4550 family are available in 28-pin and 40/44-pin packages. Block diagrams for the two groups are shown in Figure 1-1 and Figure 1-2. The devices are differentiated from each other in six ways: 1. Flash program memory (24 Kbytes for PIC18FX455 devices, 32 Kbytes for PIC18FX550 devices). 2. A/D channels (10 for 28-pin devices, 13 for 40/44-pin devices). 3. I/O ports (3 bidirectional ports and 1 input only port on 28-pin devices, 5 bidirectional ports on 40/44-pin devices). 4. CCP and Enhanced CCP implementation (28-pin devices have two standard CCP modules, 40/44-pin devices have one standard CCP module and one ECCP module). 5. Streaming Parallel Port (present only on 40/44-pin devices). All other features for devices in this family are identical. These are summarized in Table 1-1. The pinouts for all devices are listed in Table 1-2 and Table 1-3. Like all Microchip PIC18 devices, members of the PIC18F2455/2550/4455/4550 family are available as both standard and low-voltage devices. Standard devices with Enhanced Flash memory, designated with an “F” in the part number (such as PIC18F2550), accommodate an operating VDD range of 4.2V to 5.5V. Low-voltage parts, designated by “LF” (such as PIC18LF2550), function over an extended VDD range of 2.0V to 5.5V. © 2009 Microchip Technology Inc. DS39632E-page 9 PIC18F2455/2550/4455/4550 TABLE 1-1: DEVICE FEATURES Features PIC18F2455 PIC18F2550 PIC18F4455 PIC18F4550 Operating Frequency DC – 48 MHz DC – 48 MHz DC – 48 MHz DC – 48 MHz Program Memory (Bytes) 24576 32768 24576 32768 Program Memory (Instructions) 12288 16384 12288 16384 Data Memory (Bytes) 2048 2048 2048 2048 Data EEPROM Memory (Bytes) 256 256 256 256 Interrupt Sources 19 19 20 20 I/O Ports Ports A, B, C, (E) Ports A, B, C, (E) Ports A, B, C, D, E Ports A, B, C, D, E Timers 4 4 4 4 Capture/Compare/PWM Modules 2 2 1 1 Enhanced Capture/ Compare/PWM Modules 0 0 1 1 Serial Communications MSSP, Enhanced USART MSSP, Enhanced USART MSSP, Enhanced USART MSSP, Enhanced USART Universal Serial Bus (USB) Module 1 1 1 1 Streaming Parallel Port (SPP) No No Yes Yes 10-Bit Analog-to-Digital Module 10 Input Channels 10 Input Channels 13 Input Channels 13 Input Channels Comparators 2 2 2 2 Resets (and Delays) POR, BOR, RESET Instruction, Stack Full, Stack Underflow (PWRT, OST), MCLR (optional), WDT POR, BOR, RESET Instruction, Stack Full, Stack Underflow (PWRT, OST), MCLR (optional), WDT POR, BOR, RESET Instruction, Stack Full, Stack Underflow (PWRT, OST), MCLR (optional), WDT POR, BOR, RESET Instruction, Stack Full, Stack Underflow (PWRT, OST), MCLR (optional), WDT Programmable Low-Voltage Detect Yes Yes Yes Yes Programmable Brown-out Reset Yes Yes Yes Yes Instruction Set 75 Instructions; 83 with Extended Instruction Set enabled 75 Instructions; 83 with Extended Instruction Set enabled 75 Instructions; 83 with Extended Instruction Set enabled 75 Instructions; 83 with Extended Instruction Set enabled Packages 28-Pin PDIP 28-Pin SOIC 28-Pin PDIP 28-Pin SOIC 40-Pin PDIP 44-Pin QFN 44-Pin TQFP 40-Pin PDIP 44-Pin QFN 44-Pin TQFP PIC18F2455/2550/4455/4550 DS39632E-page 10 © 2009 Microchip Technology Inc. FIGURE 1-1: PIC18F2455/2550 (28-PIN) BLOCK DIAGRAM Data Latch Data Memory (2 Kbytes) Address Latch Data Address<12> 12 BSR Access 4 4 PCH PCL PCLATH 8 31 Level Stack Program Counter PRODH PRODL 8 x 8 Multiply 8 8 8 ALU<8> Address Latch Program Memory (24/32 Kbytes) Data Latch 20 8 8 Table Pointer<21> inc/dec logic 21 8 Data Bus<8> Table Latch 8 IR 12 3 ROM Latch PCLATU PCU PORTE MCLR/VPP/RE3(1) Note 1: RE3 is multiplexed with MCLR and is only available when the MCLR Resets are disabled. 2: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O. Refer to Section 2.0 “Oscillator Configurations” for additional information. 3: RB3 is the alternate pin for CCP2 multiplexing. W Instruction Bus <16> STKPTR Bank 8 8 8 BITOP FSR0 FSR1 FSR2 inc/dec Address 12 Decode logic Comparator MSSP EUSART 10-Bit ADC HLVD Timer0 Timer1 Timer2 Timer3 CCP2 BOR Data EEPROM USB Instruction Decode & Control State Machine Control Signals Power-up Timer Oscillator Start-up Timer Power-on Reset Watchdog Timer OSC1(2) OSC2(2) VDD, Brown-out Reset Internal Oscillator Fail-Safe Clock Monitor Reference Band Gap VSS MCLR(1) Block INTRC Oscillator 8 MHz Oscillator Single-Supply Programming In-Circuit Debugger T1OSI T1OSO USB Voltage VUSB Regulator PORTB PORTC RB0/AN12/INT0/FLT0/SDI/SDA RC0/T1OSO/T13CKI RC1/T1OSI/CCP2(3)/UOE RC2/CCP1 RC4/D-/VM RC5/D+/VP RC6/TX/CK RC7/RX/DT/SDO RB1/AN10/INT1/SCK/SCL RB2/AN8/INT2/VMO RB3/AN9/CCP2(3)/VPO RB4/AN11/KBI0 RB5/KBI1/PGM RB6/KBI2/PGC RB7/KBI3/PGD PORTA RA4/T0CKI/C1OUT/RCV RA5/AN4/SS/HLVDIN/C2OUT RA3/AN3/VREF+ RA2/AN2/VREF-/CVREF RA1/AN1 RA0/AN0 OSC2/CLKO/RA6 CCP1 © 2009 Microchip Technology Inc. DS39632E-page 11 PIC18F2455/2550/4455/4550 FIGURE 1-2: PIC18F4455/4550 (40/44-PIN) BLOCK DIAGRAM Instruction Decode & Control Data Latch Data Memory (2 Kbytes) Address Latch Data Address<12> 12 BSR Access 4 4 PCH PCL PCLATH 8 31 Level Stack Program Counter PRODH PRODL 8 x 8 Multiply 8 BITOP 8 8 ALU<8> Address Latch Program Memory (24/32 Kbytes) Data Latch 20 8 8 Table Pointer<21> inc/dec logic 21 8 Data Bus<8> Table Latch 8 IR 12 3 ROM Latch PORTD RD0/SPP0:RD4/SPP4 PCLATU PCU PORTE MCLR/VPP/RE3(1) RE2/AN7/OESPP RE0/AN5/CK1SPP RE1/AN6/CK2SPP Note 1: RE3 is multiplexed with MCLR and is only available when the MCLR Resets are disabled. 2: OSC1/CLKI and OSC2/CLKO are only available in select oscillator modes and when these pins are not being used as digital I/O. Refer to Section 2.0 “Oscillator Configurations” for additional information. 3: These pins are only available on 44-pin TQFP packages under certain conditions. Refer to Section 25.9 “Special ICPORT Features (44-Pin TQFP Package Only)” for additional information. 4: RB3 is the alternate pin for CCP2 multiplexing. Comparator MSSP EUSART 10-Bit ADC Timer0 Timer1 Timer2 Timer3 CCP2 HLVD ECCP1 BOR Data EEPROM W Instruction Bus <16> STKPTR Bank 8 State Machine Control Signals 8 8 Power-up Timer Oscillator Start-up Timer Power-on Reset Watchdog Timer OSC1(2) OSC2(2) VDD, VSS Brown-out Reset Internal Oscillator Fail-Safe Clock Monitor Reference Band Gap MCLR(1) Block INTRC Oscillator 8 MHz Oscillator Single-Supply Programming In-Circuit Debugger T1OSI T1OSO RD5/SPP5/P1B RD6/SPP6/P1C RD7/SPP7/P1D PORTA PORTB PORTC RA4/T0CKI/C1OUT/RCV RA5/AN4/SS/HLVDIN/C2OUT RB0/AN12/INT0/FLT0/SDI/SDA RC0/T1OSO/T13CKI RC1/T1OSI/CCP2(4)/UOE RC2/CCP1/P1A RC4/D-/VM RC5/D+/VP RC6/TX/CK RC7/RX/DT/SDO RA3/AN3/VREF+ RA2/AN2/VREF-/CVREF RA1/AN1 RA0/AN0 RB1/AN10/INT1/SCK/SCL RB2/AN8/INT2/VMO RB3/AN9/CCP2(4)/VPO OSC2/CLKO/RA6 RB4/AN11/KBI0/CSSPP RB5/KBI1/PGM RB6/KBI2/PGC RB7/KBI3/PGD USB FSR0 FSR1 FSR2 inc/dec Address 12 Decode logic USB Voltage Regulator VUSB ICRST(3) ICPGC(3) ICPGD(3) ICPORTS(3) PIC18F2455/2550/4455/4550 DS39632E-page 12 © 2009 Microchip Technology Inc. TABLE 1-2: PIC18F2455/2550 PINOUT I/O DESCRIPTIONS Pin Name Pin Number Pin Type Buffer Type Description PDIP, SOIC MCLR/VPP/RE3 MCLR VPP RE3 1 I PI ST ST Master Clear (input) or programming voltage (input). Master Clear (Reset) input. This pin is an active-low Reset to the device. Programming voltage input. Digital input. OSC1/CLKI OSC1 CLKI 9 II Analog Analog Oscillator crystal or external clock input. Oscillator crystal input or external clock source input. External clock source input. Always associated with pin function OSC1. (See OSC2/CLKO pin.) OSC2/CLKO/RA6 OSC2 CLKO RA6 10 O O I/O — — TTL Oscillator crystal or clock output. Oscillator crystal output. Connects to crystal or resonator in Crystal Oscillator mode. In select modes, OSC2 pin outputs CLKO which has 1/4 the frequency of OSC1 and denotes the instruction cycle rate. General purpose I/O pin. Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. © 2009 Microchip Technology Inc. DS39632E-page 13 PIC18F2455/2550/4455/4550 PORTA is a bidirectional I/O port. RA0/AN0 RA0 AN0 2 I/O I TTL Analog Digital I/O. Analog input 0. RA1/AN1 RA1 AN1 3 I/O I TTL Analog Digital I/O. Analog input 1. RA2/AN2/VREF-/CVREF RA2 AN2 VREFCVREF 4 I/O IIO TTL Analog Analog Analog Digital I/O. Analog input 2. A/D reference voltage (low) input. Analog comparator reference output. RA3/AN3/VREF+ RA3 AN3 VREF+ 5 I/O II TTL Analog Analog Digital I/O. Analog input 3. A/D reference voltage (high) input. RA4/T0CKI/C1OUT/RCV RA4 T0CKI C1OUT RCV 6 I/O IOI ST ST — TTL Digital I/O. Timer0 external clock input. Comparator 1 output. External USB transceiver RCV input. RA5/AN4/SS/ HLVDIN/C2OUT RA5 AN4 SS HLVDIN C2OUT 7 I/O IIIO TTL Analog TTL Analog — Digital I/O. Analog input 4. SPI slave select input. High/Low-Voltage Detect input. Comparator 2 output. RA6 — — — See the OSC2/CLKO/RA6 pin. TABLE 1-2: PIC18F2455/2550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP, SOIC Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. PIC18F2455/2550/4455/4550 DS39632E-page 14 © 2009 Microchip Technology Inc. PORTB is a bidirectional I/O port. PORTB can be software programmed for internal weak pull-ups on all inputs. RB0/AN12/INT0/FLT0/ SDI/SDA RB0 AN12 INT0 FLT0 SDI SDA 21 I/O IIII I/O TTL Analog ST ST ST ST Digital I/O. Analog input 12. External interrupt 0. PWM Fault input (CCP1 module). SPI data in. I2C™ data I/O. RB1/AN10/INT1/SCK/ SCL RB1 AN10 INT1 SCK SCL 22 I/O II I/O I/O TTL Analog ST ST ST Digital I/O. Analog input 10. External interrupt 1. Synchronous serial clock input/output for SPI mode. Synchronous serial clock input/output for I2C mode. RB2/AN8/INT2/VMO RB2 AN8 INT2 VMO 23 I/O IIO TTL Analog ST — Digital I/O. Analog input 8. External interrupt 2. External USB transceiver VMO output. RB3/AN9/CCP2/VPO RB3 AN9 CCP2(1) VPO 24 I/O I I/O O TTL Analog ST — Digital I/O. Analog input 9. Capture 2 input/Compare 2 output/PWM2 output. External USB transceiver VPO output. RB4/AN11/KBI0 RB4 AN11 KBI0 25 I/O II TTL Analog TTL Digital I/O. Analog input 11. Interrupt-on-change pin. RB5/KBI1/PGM RB5 KBI1 PGM 26 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. Low-Voltage ICSP™ Programming enable pin. RB6/KBI2/PGC RB6 KBI2 PGC 27 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. In-Circuit Debugger and ICSP programming clock pin. RB7/KBI3/PGD RB7 KBI3 PGD 28 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. In-Circuit Debugger and ICSP programming data pin. TABLE 1-2: PIC18F2455/2550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP, SOIC Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. © 2009 Microchip Technology Inc. DS39632E-page 15 PIC18F2455/2550/4455/4550 PORTC is a bidirectional I/O port. RC0/T1OSO/T13CKI RC0 T1OSO T13CKI 11 I/O OI ST — ST Digital I/O. Timer1 oscillator output. Timer1/Timer3 external clock input. RC1/T1OSI/CCP2/UOE RC1 T1OSI CCP2(2) UOE 12 I/O I I/O O ST CMOS ST — Digital I/O. Timer1 oscillator input. Capture 2 input/Compare 2 output/PWM2 output. External USB transceiver OE output. RC2/CCP1 RC2 CCP1 13 I/O I/O ST ST Digital I/O. Capture 1 input/Compare 1 output/PWM1 output. RC4/D-/VM RC4 DVM 15 I I/O I TTL — TTL Digital input. USB differential minus line (input/output). External USB transceiver VM input. RC5/D+/VP RC5 D+ VP 16 I I/O O TTL — TTL Digital input. USB differential plus line (input/output). External USB transceiver VP input. RC6/TX/CK RC6 TX CK 17 I/O O I/O ST — ST Digital I/O. EUSART asynchronous transmit. EUSART synchronous clock (see RX/DT). RC7/RX/DT/SDO RC7 RX DT SDO 18 I/O I I/O O ST ST ST — Digital I/O. EUSART asynchronous receive. EUSART synchronous data (see TX/CK). SPI data out. RE3 — — — See MCLR/VPP/RE3 pin. VUSB 14 P — Internal USB 3.3V voltage regulator output, positive supply for internal USB transceiver. VSS 8, 19 P — Ground reference for logic and I/O pins. VDD 20 P — Positive supply for logic and I/O pins. TABLE 1-2: PIC18F2455/2550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP, SOIC Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. PIC18F2455/2550/4455/4550 DS39632E-page 16 © 2009 Microchip Technology Inc. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP MCLR/VPP/RE3 MCLR VPP RE3 1 18 18 I PI ST ST Master Clear (input) or programming voltage (input). Master Clear (Reset) input. This pin is an active-low Reset to the device. Programming voltage input. Digital input. OSC1/CLKI OSC1 CLKI 13 32 30 II Analog Analog Oscillator crystal or external clock input. Oscillator crystal input or external clock source input. External clock source input. Always associated with pin function OSC1. (See OSC2/CLKO pin.) OSC2/CLKO/RA6 OSC2 CLKO RA6 14 33 31 O O I/O — — TTL Oscillator crystal or clock output. Oscillator crystal output. Connects to crystal or resonator in Crystal Oscillator mode. In RC mode, OSC2 pin outputs CLKO which has 1/4 the frequency of OSC1 and denotes the instruction cycle rate. General purpose I/O pin. Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. © 2009 Microchip Technology Inc. DS39632E-page 17 PIC18F2455/2550/4455/4550 PORTA is a bidirectional I/O port. RA0/AN0 RA0 AN0 2 19 19 I/O I TTL Analog Digital I/O. Analog input 0. RA1/AN1 RA1 AN1 3 20 20 I/O I TTL Analog Digital I/O. Analog input 1. RA2/AN2/VREF-/ CVREF RA2 AN2 VREFCVREF 4 21 21 I/O IIO TTL Analog Analog Analog Digital I/O. Analog input 2. A/D reference voltage (low) input. Analog comparator reference output. RA3/AN3/VREF+ RA3 AN3 VREF+ 5 22 22 I/O II TTL Analog Analog Digital I/O. Analog input 3. A/D reference voltage (high) input. RA4/T0CKI/C1OUT/ RCV RA4 T0CKI C1OUT RCV 6 23 23 I/O IOI ST ST — TTL Digital I/O. Timer0 external clock input. Comparator 1 output. External USB transceiver RCV input. RA5/AN4/SS/ HLVDIN/C2OUT RA5 AN4 SS HLVDIN C2OUT 7 24 24 I/O IIIO TTL Analog TTL Analog — Digital I/O. Analog input 4. SPI slave select input. High/Low-Voltage Detect input. Comparator 2 output. RA6 — — — — — See the OSC2/CLKO/RA6 pin. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. PIC18F2455/2550/4455/4550 DS39632E-page 18 © 2009 Microchip Technology Inc. PORTB is a bidirectional I/O port. PORTB can be software programmed for internal weak pull-ups on all inputs. RB0/AN12/INT0/ FLT0/SDI/SDA RB0 AN12 INT0 FLT0 SDI SDA 33 9 8 I/O IIII I/O TTL Analog ST ST ST ST Digital I/O. Analog input 12. External interrupt 0. Enhanced PWM Fault input (ECCP1 module). SPI data in. I2C™ data I/O. RB1/AN10/INT1/SCK/ SCL RB1 AN10 INT1 SCK SCL 34 10 9 I/O II I/O I/O TTL Analog ST ST ST Digital I/O. Analog input 10. External interrupt 1. Synchronous serial clock input/output for SPI mode. Synchronous serial clock input/output for I2C mode. RB2/AN8/INT2/VMO RB2 AN8 INT2 VMO 35 11 10 I/O IIO TTL Analog ST — Digital I/O. Analog input 8. External interrupt 2. External USB transceiver VMO output. RB3/AN9/CCP2/VPO RB3 AN9 CCP2(1) VPO 36 12 11 I/O I I/O O TTL Analog ST — Digital I/O. Analog input 9. Capture 2 input/Compare 2 output/PWM2 output. External USB transceiver VPO output. RB4/AN11/KBI0/CSSPP RB4 AN11 KBI0 CSSPP 37 14 14 I/O IIO TTL Analog TTL — Digital I/O. Analog input 11. Interrupt-on-change pin. SPP chip select control output. RB5/KBI1/PGM RB5 KBI1 PGM 38 15 15 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. Low-Voltage ICSP™ Programming enable pin. RB6/KBI2/PGC RB6 KBI2 PGC 39 16 16 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. In-Circuit Debugger and ICSP programming clock pin. RB7/KBI3/PGD RB7 KBI3 PGD 40 17 17 I/O I I/O TTL TTL ST Digital I/O. Interrupt-on-change pin. In-Circuit Debugger and ICSP programming data pin. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. © 2009 Microchip Technology Inc. DS39632E-page 19 PIC18F2455/2550/4455/4550 PORTC is a bidirectional I/O port. RC0/T1OSO/T13CKI RC0 T1OSO T13CKI 15 34 32 I/O OI ST — ST Digital I/O. Timer1 oscillator output. Timer1/Timer3 external clock input. RC1/T1OSI/CCP2/ UOE RC1 T1OSI CCP2(2) UOE 16 35 35 I/O I I/O O ST CMOS ST — Digital I/O. Timer1 oscillator input. Capture 2 input/Compare 2 output/PWM2 output. External USB transceiver OE output. RC2/CCP1/P1A RC2 CCP1 P1A 17 36 36 I/O I/O O ST ST TTL Digital I/O. Capture 1 input/Compare 1 output/PWM1 output. Enhanced CCP1 PWM output, channel A. RC4/D-/VM RC4 DVM 23 42 42 I I/O I TTL — TTL Digital input. USB differential minus line (input/output). External USB transceiver VM input. RC5/D+/VP RC5 D+ VP 24 43 43 I I/O I TTL — TTL Digital input. USB differential plus line (input/output). External USB transceiver VP input. RC6/TX/CK RC6 TX CK 25 44 44 I/O O I/O ST — ST Digital I/O. EUSART asynchronous transmit. EUSART synchronous clock (see RX/DT). RC7/RX/DT/SDO RC7 RX DT SDO 26 1 1 I/O I I/O O ST ST ST — Digital I/O. EUSART asynchronous receive. EUSART synchronous data (see TX/CK). SPI data out. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. PIC18F2455/2550/4455/4550 DS39632E-page 20 © 2009 Microchip Technology Inc. PORTD is a bidirectional I/O port or a Streaming Parallel Port (SPP). These pins have TTL input buffers when the SPP module is enabled. RD0/SPP0 RD0 SPP0 19 38 38 I/O I/O ST TTL Digital I/O. Streaming Parallel Port data. RD1/SPP1 RD1 SPP1 20 39 39 I/O I/O ST TTL Digital I/O. Streaming Parallel Port data. RD2/SPP2 RD2 SPP2 21 40 40 I/O I/O ST TTL Digital I/O. Streaming Parallel Port data. RD3/SPP3 RD3 SPP3 22 41 41 I/O I/O ST TTL Digital I/O. Streaming Parallel Port data. RD4/SPP4 RD4 SPP4 27 2 2 I/O I/O ST TTL Digital I/O. Streaming Parallel Port data. RD5/SPP5/P1B RD5 SPP5 P1B 28 3 3 I/O I/O O ST TTL — Digital I/O. Streaming Parallel Port data. Enhanced CCP1 PWM output, channel B. RD6/SPP6/P1C RD6 SPP6 P1C 29 4 4 I/O I/O O ST TTL — Digital I/O. Streaming Parallel Port data. Enhanced CCP1 PWM output, channel C. RD7/SPP7/P1D RD7 SPP7 P1D 30 5 5 I/O I/O O ST TTL — Digital I/O. Streaming Parallel Port data. Enhanced CCP1 PWM output, channel D. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. © 2009 Microchip Technology Inc. DS39632E-page 21 PIC18F2455/2550/4455/4550 PORTE is a bidirectional I/O port. RE0/AN5/CK1SPP RE0 AN5 CK1SPP 8 25 25 I/O IO ST Analog — Digital I/O. Analog input 5. SPP clock 1 output. RE1/AN6/CK2SPP RE1 AN6 CK2SPP 9 26 26 I/O IO ST Analog — Digital I/O. Analog input 6. SPP clock 2 output. RE2/AN7/OESPP RE2 AN7 OESPP 10 27 27 I/O IO ST Analog — Digital I/O. Analog input 7. SPP output enable output. RE3 — — — — — See MCLR/VPP/RE3 pin. VSS 12, 31 6, 30, 31 6, 29 P — Ground reference for logic and I/O pins. VDD 11, 32 7, 8, 28, 29 7, 28 P — Positive supply for logic and I/O pins. VUSB 18 37 37 P — Internal USB 3.3V voltage regulator output, positive supply for the USB transceiver. NC/ICCK/ICPGC(3) ICCK ICPGC — — 12 I/O I/O ST ST No Connect or dedicated ICD/ICSP™ port clock. In-Circuit Debugger clock. ICSP programming clock. NC/ICDT/ICPGD(3) ICDT ICPGD — — 13 I/O I/O ST ST No Connect or dedicated ICD/ICSP port clock. In-Circuit Debugger data. ICSP programming data. NC/ICRST/ICVPP(3) ICRST ICVPP — — 33 IP —— No Connect or dedicated ICD/ICSP port Reset. Master Clear (Reset) input. Programming voltage input. NC/ICPORTS(3) ICPORTS — — 34 P — No Connect or 28-pin device emulation. Enable 28-pin device emulation when connected to VSS. NC — 13 — — — No Connect. TABLE 1-3: PIC18F4455/4550 PINOUT I/O DESCRIPTIONS (CONTINUED) Pin Name Pin Number Pin Type Buffer Type Description PDIP QFN TQFP Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output ST = Schmitt Trigger input with CMOS levels I = Input O = Output P = Power Note 1: Alternate assignment for CCP2 when CCP2MX Configuration bit is cleared. 2: Default assignment for CCP2 when CCP2MX Configuration bit is set. 3: These pins are No Connect unless the ICPRT Configuration bit is set. For NC/ICPORTS, the pin is No Connect unless ICPRT is set and the DEBUG Configuration bit is cleared. PIC18F2455/2550/4455/4550 DS39632E-page 22 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 23 PIC18F2455/2550/4455/4550 2.0 OSCILLATOR CONFIGURATIONS 2.1 Overview Devices in the PIC18F2455/2550/4455/4550 family incorporate a different oscillator and microcontroller clock system than previous PIC18F devices. The addition of the USB module, with its unique requirements for a stable clock source, make it necessary to provide a separate clock source that is compliant with both USB low-speed and full-speed specifications. To accommodate these requirements, PIC18F2455/ 2550/4455/4550 devices include a new clock branch to provide a 48 MHz clock for full-speed USB operation. Since it is driven from the primary clock source, an additional system of prescalers and postscalers has been added to accommodate a wide range of oscillator frequencies. An overview of the oscillator structure is shown in Figure 2-1. Other oscillator features used in PIC18 enhanced microcontrollers, such as the internal oscillator block and clock switching, remain the same. They are discussed later in this chapter. 2.1.1 OSCILLATOR CONTROL The operation of the oscillator in PIC18F2455/2550/ 4455/4550 devices is controlled through two Configuration registers and two control registers. Configuration registers, CONFIG1L and CONFIG1H, select the oscillator mode and USB prescaler/postscaler options. As Configuration bits, these are set when the device is programmed and left in that configuration until the device is reprogrammed. The OSCCON register (Register 2-2) selects the Active Clock mode; it is primarily used in controlling clock switching in power-managed modes. Its use is discussed in Section 2.4.1 “Oscillator Control Register”. The OSCTUNE register (Register 2-1) is used to trim the INTRC frequency source, as well as select the low-frequency clock source that drives several special features. Its use is described in Section 2.2.5.2 “OSCTUNE Register”. 2.2 Oscillator Types PIC18F2455/2550/4455/4550 devices can be operated in twelve distinct oscillator modes. In contrast with previous PIC18 enhanced microcontrollers, four of these modes involve the use of two oscillator types at once. Users can program the FOSC3:FOSC0 Configuration bits to select one of these modes: 1. XT Crystal/Resonator 2. HS High-Speed Crystal/Resonator 3. HSPLL High-Speed Crystal/Resonator with PLL Enabled 4. EC External Clock with FOSC/4 Output 5. ECIO External Clock with I/O on RA6 6. ECPLL External Clock with PLL Enabled and FOSC/4 Output on RA6 7. ECPIO External Clock with PLL Enabled, I/O on RA6 8. INTHS Internal Oscillator used as Microcontroller Clock Source, HS Oscillator used as USB Clock Source 9. INTIO Internal Oscillator used as Microcontroller Clock Source, EC Oscillator used as USB Clock Source, Digital I/O on RA6 10. INTCKO Internal Oscillator used as Microcontroller Clock Source, EC Oscillator used as USB Clock Source, FOSC/4 Output on RA6 2.2.1 OSCILLATOR MODES AND USB OPERATION Because of the unique requirements of the USB module, a different approach to clock operation is necessary. In previous PIC® devices, all core and peripheral clocks were driven by a single oscillator source; the usual sources were primary, secondary or the internal oscillator. With PIC18F2455/2550/4455/4550 devices, the primary oscillator becomes part of the USB module and cannot be associated to any other clock source. Thus, the USB module must be clocked from the primary clock source; however, the microcontroller core and other peripherals can be separately clocked from the secondary or internal oscillators as before. Because of the timing requirements imposed by USB, an internal clock of either 6 MHz or 48 MHz is required while the USB module is enabled. Fortunately, the microcontroller and other peripherals are not required to run at this clock speed when using the primary oscillator. There are numerous options to achieve the USB module clock requirement and still provide flexibility for clocking the rest of the device from the primary oscillator source. These are detailed in Section 2.3 “Oscillator Settings for USB”. PIC18F2455/2550/4455/4550 DS39632E-page 24 © 2009 Microchip Technology Inc. FIGURE 2-1: PIC18F2455/2550/4455/4550 CLOCK DIAGRAM PIC18F2455/2550/4455/4550 FOSC3:FOS C0 Secondary Oscillator T1OSCEN Enable Oscillator T1OSO T1OSI Clock Source Option for Other Modules OSC1 OSC2 Sleep Primary Oscillator XT, HS, EC, ECIO T1OSC CPU Peripherals IDLEN INTOSC Postscaler MUX MUX 8 MHz 4 MHz 2 MHz 1 MHz 500 kHz 125 kHz 250 kHz OSCCON<6:4> 111 110 101 100 011 010 001 31 kHz 000 INTRC Source Internal Oscillator Block WDT, PWRT, FSCM 8 MHz Internal Oscillator (INTOSC) Clock Control Source OSCCON< 1:0> 8 MHz 31 kHz (INTRC) 0 1 OSCTUNE<7> and Two-Speed Start-up 96 MHz PLL PLLDIV CPUDIV 0 1 0 ÷ 2 1 PLL Prescaler MUX 111 110 101 100 011 010 001 000 ÷ 1 ÷ 2 ÷ 3 ÷ 4 ÷ 5 ÷ 6 ÷ 10 ÷ 12 11 10 01 00 PLL Postscaler ÷ 2 ÷ 3 ÷ 4 ÷ 6 USB USBDIV FOSC3:FOSC0 HSPLL, ECPLL, 11 10 01 00 Oscillator Postscaler ÷ 1 ÷ 2 ÷ 3 ÷ 4 CPUDIV 1 0 Peripheral FSEN ÷ 4 USB Clock Source XTPLL, ECPIO Primary Clock (4 MHz Input Only) © 2009 Microchip Technology Inc. DS39632E-page 25 PIC18F2455/2550/4455/4550 2.2.2 CRYSTAL OSCILLATOR/CERAMIC RESONATORS In HS, HSPLL, XT and XTPLL Oscillator modes, a crystal or ceramic resonator is connected to the OSC1 and OSC2 pins to establish oscillation. Figure 2-2 shows the pin connections. The oscillator design requires the use of a parallel cut crystal. FIGURE 2-2: CRYSTAL/CERAMIC RESONATOR OPERATION (XT, HS OR HSPLL CONFIGURATION) TABLE 2-1: CAPACITOR SELECTION FOR CERAMIC RESONATORS Note: Use of a series cut crystal may give a frequency out of the crystal manufacturer’s specifications. Note 1: See Table 2-1 and Table 2-2 for initial values of C1 and C2. 2: A series resistor (RS) may be required for AT strip cut crystals. 3: RF varies with the oscillator mode chosen. C1(1) C2(1) XTAL OSC2 OSC1 RF(3) Sleep To Logic PIC18FXXXX RS(2) Internal Typical Capacitor Values Used: Mode Freq OSC1 OSC2 XT 4.0 MHz 33 pF 33 pF HS 8.0 MHz 16.0 MHz 27 pF 22 pF 27 pF 22 pF Capacitor values are for design guidance only. These capacitors were tested with the resonators listed below for basic start-up and operation. These values are not optimized. Different capacitor values may be required to produce acceptable oscillator operation. The user should test the performance of the oscillator over the expected VDD and temperature range for the application. See the notes following Table 2-2 for additional information. Resonators Used: 4.0 MHz 8.0 MHz 16.0 MHz When using ceramic resonators with frequencies above 3.5 MHz, HS mode is recommended over XT mode. HS mode may be used at any VDD for which the controller is rated. If HS is selected, the gain of the oscillator may overdrive the resonator. Therefore, a series resistor should be placed between the OSC2 pin and the resonator. As a good starting point, the recommended value of RS is 330 Ω. PIC18F2455/2550/4455/4550 DS39632E-page 26 © 2009 Microchip Technology Inc. TABLE 2-2: CAPACITOR SELECTION FOR CRYSTAL OSCILLATOR An internal postscaler allows users to select a clock frequency other than that of the crystal or resonator. Frequency division is determined by the CPUDIV Configuration bits. Users may select a clock frequency of the oscillator frequency, or 1/2, 1/3 or 1/4 of the frequency. An external clock may also be used when the microcontroller is in HS Oscillator mode. In this case, the OSC2/CLKO pin is left open (Figure 2-3). FIGURE 2-3: EXTERNAL CLOCK INPUT OPERATION (HS OSC CONFIGURATION) 2.2.3 EXTERNAL CLOCK INPUT The EC, ECIO, ECPLL and ECPIO Oscillator modes require an external clock source to be connected to the OSC1 pin. There is no oscillator start-up time required after a Power-on Reset or after an exit from Sleep mode. In the EC and ECPLL Oscillator modes, the oscillator frequency divided by 4 is available on the OSC2 pin. This signal may be used for test purposes or to synchronize other logic. Figure 2-4 shows the pin connections for the EC Oscillator mode. FIGURE 2-4: EXTERNAL CLOCK INPUT OPERATION (EC AND ECPLL CONFIGURATION) The ECIO and ECPIO Oscillator modes function like the EC and ECPLL modes, except that the OSC2 pin becomes an additional general purpose I/O pin. The I/O pin becomes bit 6 of PORTA (RA6). Figure 2-5 shows the pin connections for the ECIO Oscillator mode. FIGURE 2-5: EXTERNAL CLOCK INPUT OPERATION (ECIO AND ECPIO CONFIGURATION) The internal postscaler for reducing clock frequency in XT and HS modes is also available in EC and ECIO modes. Osc Type Crystal Freq Typical Capacitor Values Tested: C1 C2 XT 4 MHz 27 pF 27 pF HS 4 MHz 27 pF 27 pF 8 MHz 22 pF 22 pF 20 MHz 15 pF 15 pF Capacitor values are for design guidance only. These capacitors were tested with the crystals listed below for basic start-up and operation. These values are not optimized. Different capacitor values may be required to produce acceptable oscillator operation. The user should test the performance of the oscillator over the expected VDD and temperature range for the application. See the notes following this table for additional information. Crystals Used: 4 MHz 8 MHz 20 MHz Note 1: Higher capacitance increases the stability of oscillator but also increases the start-up time. 2: When operating below 3V VDD, or when using certain ceramic resonators at any voltage, it may be necessary to use the HS mode or switch to a crystal oscillator. 3: Since each resonator/crystal has its own characteristics, the user should consult the resonator/crystal manufacturer for appropriate values of external components. 4: Rs may be required to avoid overdriving crystals with low drive level specification. 5: Always verify oscillator performance over the VDD and temperature range that is expected for the application. OSC1 Open OSC2 Clock from Ext. System PIC18FXXXX (HS Mode) OSC1/CLKI FOSC/4 OSC2/CLKO Clock from Ext. System PIC18FXXXX OSC1/CLKI RA6 I/O (OSC2) Clock from Ext. System PIC18FXXXX © 2009 Microchip Technology Inc. DS39632E-page 27 PIC18F2455/2550/4455/4550 2.2.4 PLL FREQUENCY MULTIPLIER PIC18F2455/2550/4255/4550 devices include a Phase Locked Loop (PLL) circuit. This is provided specifically for USB applications with lower speed oscillators and can also be used as a microcontroller clock source. The PLL is enabled in HSPLL, XTPLL, ECPLL and ECPIO Oscillator modes. It is designed to produce a fixed 96 MHz reference clock from a fixed 4 MHz input. The output can then be divided and used for both the USB and the microcontroller core clock. Because the PLL has a fixed frequency input and output, there are eight prescaling options to match the oscillator input frequency to the PLL. There is also a separate postscaler option for deriving the microcontroller clock from the PLL. This allows the USB peripheral and microcontroller to use the same oscillator input and still operate at different clock speeds. In contrast to the postscaler for XT, HS and EC modes, the available options are 1/2, 1/3, 1/4 and 1/6 of the PLL output. The HSPLL, ECPLL and ECPIO modes make use of the HS mode oscillator for frequencies up to 48 MHz. The prescaler divides the oscillator input by up to 12 to produce the 4 MHz drive for the PLL. The XTPLL mode can only use an input frequency of 4 MHz which drives the PLL directly. FIGURE 2-6: PLL BLOCK DIAGRAM (HS MODE) 2.2.5 INTERNAL OSCILLATOR BLOCK The PIC18F2455/2550/4455/4550 devices include an internal oscillator block which generates two different clock signals; either can be used as the microcontroller’s clock source. If the USB peripheral is not used, the internal oscillator may eliminate the need for external oscillator circuits on the OSC1 and/or OSC2 pins. The main output (INTOSC) is an 8 MHz clock source which can be used to directly drive the device clock. It also drives the INTOSC postscaler which can provide a range of clock frequencies from 31 kHz to 4 MHz. The INTOSC output is enabled when a clock frequency from 125 kHz to 8 MHz is selected. The other clock source is the internal RC oscillator (INTRC) which provides a nominal 31 kHz output. INTRC is enabled if it is selected as the device clock source; it is also enabled automatically when any of the following are enabled: • Power-up Timer • Fail-Safe Clock Monitor • Watchdog Timer • Two-Speed Start-up These features are discussed in greater detail in Section 25.0 “Special Features of the CPU”. The clock source frequency (INTOSC direct, INTRC direct or INTOSC postscaler) is selected by configuring the IRCF bits of the OSCCON register (page 33). 2.2.5.1 Internal Oscillator Modes When the internal oscillator is used as the microcontroller clock source, one of the other oscillator modes (External Clock or External Crystal/Resonator) must be used as the USB clock source. The choice of the USB clock source is determined by the particular internal oscillator mode. There are four distinct modes available: 1. INTHS mode: The USB clock is provided by the oscillator in HS mode. 2. INTXT mode: The USB clock is provided by the oscillator in XT mode. 3. INTCKO mode: The USB clock is provided by an external clock input on OSC1/CLKI; the OSC2/ CLKO pin outputs FOSC/4. 4. INTIO mode: The USB clock is provided by an external clock input on OSC1/CLKI; the OSC2/ CLKO pin functions as a digital I/O (RA6). Of these four modes, only INTIO mode frees up an additional pin (OSC2/CLKO/RA6) for port I/O use. MUX VCO Loop Filter and Prescaler OSC2 OSC1 PLL Enable FIN FOUT SYSCLK Phase Comparator HS/EC/ECIO/XT Oscillator Enable ÷24 (from CONFIG1H Register) Oscillator PIC18F2455/2550/4455/4550 DS39632E-page 28 © 2009 Microchip Technology Inc. 2.2.5.2 OSCTUNE Register The internal oscillator’s output has been calibrated at the factory but can be adjusted in the user’s application. This is done by writing to the OSCTUNE register (Register 2-1). The tuning sensitivity is constant throughout the tuning range. The INTOSC clock will stabilize within 1 ms. Code execution continues during this shift. There is no indication that the shift has occurred. The OSCTUNE register also contains the INTSRC bit. The INTSRC bit allows users to select which internal oscillator provides the clock source when the 31 kHz frequency option is selected. This is covered in greater detail in Section 2.4.1 “Oscillator Control Register”. 2.2.5.3 Internal Oscillator Output Frequency and Drift The internal oscillator block is calibrated at the factory to produce an INTOSC output frequency of 8.0 MHz. However, this frequency may drift as VDD or temperature changes, which can affect the controller operation in a variety of ways. The low-frequency INTRC oscillator operates independently of the INTOSC source. Any changes in INTOSC across voltage and temperature are not necessarily reflected by changes in INTRC and vice versa. REGISTER 2-1: OSCTUNE: OSCILLATOR TUNING REGISTER R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 INTSRC — — TUN4 TUN3 TUN2 TUN1 TUN0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 INTSRC: Internal Oscillator Low-Frequency Source Select bit 1 = 31.25 kHz device clock derived from 8 MHz INTOSC source (divide-by-256 enabled) 0 = 31 kHz device clock derived directly from INTRC internal oscillator bit 6-5 Unimplemented: Read as ‘0’ bit 4-0 TUN4:TUN0: Frequency Tuning bits 01111 = Maximum frequency • • • • 00001 00000 = Center frequency. Oscillator module is running at the calibrated frequency. 11111 • • • • 10000 = Minimum frequency © 2009 Microchip Technology Inc. DS39632E-page 29 PIC18F2455/2550/4455/4550 2.2.5.4 Compensating for INTOSC Drift It is possible to adjust the INTOSC frequency by modifying the value in the OSCTUNE register. This has no effect on the INTRC clock source frequency. Tuning the INTOSC source requires knowing when to make the adjustment, in which direction it should be made and in some cases, how large a change is needed. When using the EUSART, for example, an adjustment may be required when it begins to generate framing errors or receives data with errors while in Asynchronous mode. Framing errors indicate that the device clock frequency is too high; to adjust for this, decrement the value in OSCTUNE to reduce the clock frequency. On the other hand, errors in data may suggest that the clock speed is too low; to compensate, increment OSCTUNE to increase the clock frequency. It is also possible to verify device clock speed against a reference clock. Two timers may be used: one timer is clocked by the peripheral clock, while the other is clocked by a fixed reference source, such as the Timer1 oscillator. Both timers are cleared but the timer clocked by the reference generates interrupts. When an interrupt occurs, the internally clocked timer is read and both timers are cleared. If the internally clocked timer value is greater than expected, then the internal oscillator block is running too fast. To adjust for this, decrement the OSCTUNE register. Finally, a CCP module can use free-running Timer1 (or Timer3), clocked by the internal oscillator block and an external event with a known period (i.e., AC power frequency). The time of the first event is captured in the CCPRxH:CCPRxL registers and is recorded for use later. When the second event causes a capture, the time of the first event is subtracted from the time of the second event. Since the period of the external event is known, the time difference between events can be calculated. If the measured time is much greater than the calculated time, the internal oscillator block is running too fast; to compensate, decrement the OSCTUNE register. If the measured time is much less than the calculated time, the internal oscillator block is running too slow; to compensate, increment the OSCTUNE register. PIC18F2455/2550/4455/4550 DS39632E-page 30 © 2009 Microchip Technology Inc. 2.3 Oscillator Settings for USB When these devices are used for USB connectivity, they must have either a 6 MHz or 48 MHz clock for USB operation, depending on whether Low-Speed or Full-Speed mode is being used. This may require some forethought in selecting an oscillator frequency and programming the device. The full range of possible oscillator configurations compatible with USB operation is shown in Table 2-3. 2.3.1 LOW-SPEED OPERATION The USB clock for Low-Speed mode is derived from the primary oscillator chain and not directly from the PLL. It is divided by 4 to produce the actual 6 MHz clock. Because of this, the microcontroller can only use a clock frequency of 24 MHz when the USB module is active and the controller clock source is one of the primary oscillator modes (XT, HS or EC, with or without the PLL). This restriction does not apply if the microcontroller clock source is the secondary oscillator or internal oscillator block. 2.3.2 RUNNING DIFFERENT USB AND MICROCONTROLLER CLOCKS The USB module, in either mode, can run asynchronously with respect to the microcontroller core and other peripherals. This means that applications can use the primary oscillator for the USB clock while the microcontroller runs from a separate clock source at a lower speed. If it is necessary to run the entire application from only one clock source, full-speed operation provides a greater selection of microcontroller clock frequencies. TABLE 2-3: OSCILLATOR CONFIGURATION OPTIONS FOR USB OPERATION Input Oscillator Frequency PLL Division (PLLDIV2:PLLDIV0) Clock Mode (FOSC3:FOSC0) MCU Clock Division (CPUDIV1:CPUDIV0) Microcontroller Clock Frequency 48 MHz N/A(1) EC, ECIO None (00) 48 MHz ÷2 (01) 24 MHz ÷3 (10) 16 MHz ÷4 (11) 12 MHz 48 MHz ÷12 (111) EC, ECIO None (00) 48 MHz ÷2 (01) 24 MHz ÷3 (10) 16 MHz ÷4 (11) 12 MHz ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 40 MHz ÷10 (110) EC, ECIO None (00) 40 MHz ÷2 (01) 20 MHz ÷3 (10) 13.33 MHz ÷4 (11) 10 MHz ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 24 MHz ÷6 (101) HS, EC, ECIO None (00) 24 MHz ÷2 (01) 12 MHz ÷3 (10) 8MHz ÷4 (11) 6MHz HSPLL, ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz Legend: All clock frequencies, except 24 MHz, are exclusively associated with full-speed USB operation (USB clock of 48 MHz). Bold is used to highlight clock selections that are compatible with low-speed USB operation (system clock of 24 MHz, USB clock of 6 MHz). Note 1: Only valid when the USBDIV Configuration bit is cleared. © 2009 Microchip Technology Inc. DS39632E-page 31 PIC18F2455/2550/4455/4550 20 MHz ÷5 (100) HS, EC, ECIO None (00) 20 MHz ÷2 (01) 10 MHz ÷3 (10) 6.67 MHz ÷4 (11) 5MHz HSPLL, ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 16 MHz ÷4 (011) HS, EC, ECIO None (00) 16 MHz ÷2 (01) 8MHz ÷3 (10) 5.33 MHz ÷4 (11) 4MHz HSPLL, ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 12 MHz ÷3 (010) HS, EC, ECIO None (00) 12 MHz ÷2 (01) 6MHz ÷3 (10) 4MHz ÷4 (11) 3MHz HSPLL, ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 8 MHz ÷2 (001) HS, EC, ECIO None (00) 8MHz ÷2 (01) 4MHz ÷3 (10) 2.67 MHz ÷4 (11) 2MHz HSPLL, ECPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz 4 MHz ÷1 (000) XT, HS, EC, ECIO None (00) 4MHz ÷2 (01) 2MHz ÷3 (10) 1.33 MHz ÷4 (11) 1MHz HSPLL, ECPLL, XTPLL, ECPIO ÷2 (00) 48 MHz ÷3 (01) 32 MHz ÷4 (10) 24 MHz ÷6 (11) 16 MHz TABLE 2-3: OSCILLATOR CONFIGURATION OPTIONS FOR USB OPERATION (CONTINUED) Input Oscillator Frequency PLL Division (PLLDIV2:PLLDIV0) Clock Mode (FOSC3:FOSC0) MCU Clock Division (CPUDIV1:CPUDIV0) Microcontroller Clock Frequency Legend: All clock frequencies, except 24 MHz, are exclusively associated with full-speed USB operation (USB clock of 48 MHz). Bold is used to highlight clock selections that are compatible with low-speed USB operation (system clock of 24 MHz, USB clock of 6 MHz). Note 1: Only valid when the USBDIV Configuration bit is cleared. PIC18F2455/2550/4455/4550 DS39632E-page 32 © 2009 Microchip Technology Inc. 2.4 Clock Sources and Oscillator Switching Like previous PIC18 enhanced devices, the PIC18F2455/2550/4455/4550 family includes a feature that allows the device clock source to be switched from the main oscillator to an alternate, low-frequency clock source. These devices offer two alternate clock sources. When an alternate clock source is enabled, the various power-managed operating modes are available. Essentially, there are three clock sources for these devices: • Primary oscillators • Secondary oscillators • Internal oscillator block The primary oscillators include the External Crystal and Resonator modes, the External Clock modes and the internal oscillator block. The particular mode is defined by the FOSC3:FOSC0 Configuration bits. The details of these modes are covered earlier in this chapter. The secondary oscillators are those external sources not connected to the OSC1 or OSC2 pins. These sources may continue to operate even after the controller is placed in a power-managed mode. PIC18F2455/2550/4455/4550 devices offer the Timer1 oscillator as a secondary oscillator. This oscillator, in all power-managed modes, is often the time base for functions such as a Real-Time Clock (RTC). Most often, a 32.768 kHz watch crystal is connected between the RC0/T1OSO/T13CKI and RC1/T1OSI/ UOE pins. Like the XT and HS Oscillator mode circuits, loading capacitors are also connected from each pin to ground. The Timer1 oscillator is discussed in greater detail in Section 12.3 “Timer1 Oscillator”. In addition to being a primary clock source, the internal oscillator block is available as a power-managed mode clock source. The INTRC source is also used as the clock source for several special features, such as the WDT and Fail-Safe Clock Monitor. 2.4.1 OSCILLATOR CONTROL REGISTER The OSCCON register (Register 2-2) controls several aspects of the device clock’s operation, both in full-power operation and in power-managed modes. The System Clock Select bits, SCS1:SCS0, select the clock source. The available clock sources are the primary clock (defined by the FOSC3:FOSC0 Configuration bits), the secondary clock (Timer1 oscillator) and the internal oscillator block. The clock source changes immediately after one or more of the bits is written to, following a brief clock transition interval. The SCS bits are cleared on all forms of Reset. The Internal Oscillator Frequency Select bits, IRCF2:IRCF0, select the frequency output of the internal oscillator block to drive the device clock. The choices are the INTRC source, the INTOSC source (8 MHz) or one of the frequencies derived from the INTOSC postscaler (31 kHz to 4 MHz). If the internal oscillator block is supplying the device clock, changing the states of these bits will have an immediate change on the internal oscillator’s output. On device Resets, the default output frequency of the internal oscillator block is set at 1 MHz. When an output frequency of 31 kHz is selected (IRCF2:IRCF0 = 000), users may choose which internal oscillator acts as the source. This is done with the INTSRC bit in the OSCTUNE register (OSCTUNE<7>). Setting this bit selects INTOSC as a 31.25 kHz clock source by enabling the divide-by-256 output of the INTOSC postscaler. Clearing INTSRC selects INTRC (nominally 31 kHz) as the clock source. This option allows users to select the tunable and more precise INTOSC as a clock source, while maintaining power savings with a very low clock speed. Regardless of the setting of INTSRC, INTRC always remains the clock source for features such as the Watchdog Timer and the Fail-Safe Clock Monitor. The OSTS, IOFS and T1RUN bits indicate which clock source is currently providing the device clock. The OSTS bit indicates that the Oscillator Start-up Timer (OST) has timed out and the primary clock is providing the device clock in primary clock modes. The IOFS bit indicates when the internal oscillator block has stabilized and is providing the device clock in RC Clock modes. The T1RUN bit (T1CON<6>) indicates when the Timer1 oscillator is providing the device clock in secondary clock modes. In power-managed modes, only one of these three bits will be set at any time. If none of these bits are set, the INTRC is providing the clock or the internal oscillator block has just started and is not yet stable. The IDLEN bit determines if the device goes into Sleep mode, or one of the Idle modes, when the SLEEP instruction is executed. The use of the flag and control bits in the OSCCON register is discussed in more detail in Section 3.0 “Power-Managed Modes”. Note 1: The Timer1 oscillator must be enabled to select the secondary clock source. The Timer1 oscillator is enabled by setting the T1OSCEN bit in the Timer1 Control register (T1CON<3>). If the Timer1 oscillator is not enabled, then any attempt to select a secondary clock source will be ignored. 2: It is recommended that the Timer1 oscillator be operating and stable prior to switching to it as the clock source; otherwise, a very long delay may occur while the Timer1 oscillator starts. © 2009 Microchip Technology Inc. DS39632E-page 33 PIC18F2455/2550/4455/4550 2.4.2 OSCILLATOR TRANSITIONS PIC18F2455/2550/4455/4550 devices contain circuitry to prevent clock “glitches” when switching between clock sources. A short pause in the device clock occurs during the clock switch. The length of this pause is the sum of two cycles of the old clock source and three to four cycles of the new clock source. This formula assumes that the new clock source is stable. Clock transitions are discussed in greater detail in Section 3.1.2 “Entering Power-Managed Modes”. REGISTER 2-2: OSCCON: OSCILLATOR CONTROL REGISTER R/W-0 R/W-1 R/W-0 R/W-0 R(1) R-0 R/W-0 R/W-0 IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 IDLEN: Idle Enable bit 1 = Device enters Idle mode on SLEEP instruction 0 = Device enters Sleep mode on SLEEP instruction bit 6-4 IRCF2:IRCF0: Internal Oscillator Frequency Select bits 111 = 8 MHz (INTOSC drives clock directly) 110 = 4 MHz 101 = 2 MHz 100 = 1 MHz(3) 011 = 500 kHz 010 = 250 kHz 001 = 125 kHz 000 = 31 kHz (from either INTOSC/256 or INTRC directly)(2) bit 3 OSTS: Oscillator Start-up Time-out Status bit(1) 1 = Oscillator Start-up Timer time-out has expired; primary oscillator is running 0 = Oscillator Start-up Timer time-out is running; primary oscillator is not ready bit 2 IOFS: INTOSC Frequency Stable bit 1 = INTOSC frequency is stable 0 = INTOSC frequency is not stable bit 1-0 SCS1:SCS0: System Clock Select bits 1x = Internal oscillator 01 = Timer1 oscillator 00 = Primary oscillator Note 1: Depends on the state of the IESO Configuration bit. 2: Source selected by the INTSRC bit (OSCTUNE<7>), see text. 3: Default output frequency of INTOSC on Reset. PIC18F2455/2550/4455/4550 DS39632E-page 34 © 2009 Microchip Technology Inc. 2.5 Effects of Power-Managed Modes on the Various Clock Sources When PRI_IDLE mode is selected, the designated primary oscillator continues to run without interruption. For all other power-managed modes, the oscillator using the OSC1 pin is disabled. Unless the USB module is enabled, the OSC1 pin (and OSC2 pin if used by the oscillator) will stop oscillating. In secondary clock modes (SEC_RUN and SEC_IDLE), the Timer1 oscillator is operating and providing the device clock. The Timer1 oscillator may also run in all power-managed modes if required to clock Timer1 or Timer3. In internal oscillator modes (RC_RUN and RC_IDLE), the internal oscillator block provides the device clock source. The 31 kHz INTRC output can be used directly to provide the clock and may be enabled to support various special features regardless of the power-managed mode (see Section 25.2 “Watchdog Timer (WDT)”, Section 25.3 “Two-Speed Start-up” and Section 25.4 “Fail-Safe Clock Monitor” for more information on WDT, Fail-Safe Clock Monitor and Two-Speed Start-up). The INTOSC output at 8 MHz may be used directly to clock the device or may be divided down by the postscaler. The INTOSC output is disabled if the clock is provided directly from the INTRC output. Regardless of the Run or Idle mode selected, the USB clock source will continue to operate. If the device is operating from a crystal or resonator-based oscillator, that oscillator will continue to clock the USB module. The core and all other modules will switch to the new clock source. If the Sleep mode is selected, all clock sources are stopped. Since all the transistor switching currents have been stopped, Sleep mode achieves the lowest current consumption of the device (only leakage currents). Sleep mode should never be invoked while the USB module is operating and connected. The only exception is when the device has been issued a “Suspend” command over the USB. Once the module has suspended operation and shifted to a low-power state, the microcontroller may be safely put into Sleep mode. Enabling any on-chip feature that will operate during Sleep will increase the current consumed during Sleep. The INTRC is required to support WDT operation. The Timer1 oscillator may be operating to support a Real-Time Clock. Other features may be operating that do not require a device clock source (i.e., MSSP slave, PSP, INTx pins and others). Peripherals that may add significant current consumption are listed in Section 28.2 “DC Characteristics: Power-Down and Supply Current”. 2.6 Power-up Delays Power-up delays are controlled by two timers so that no external Reset circuitry is required for most applications. The delays ensure that the device is kept in Reset until the device power supply is stable under normal circumstances and the primary clock is operating and stable. For additional information on power-up delays, see Section 4.5 “Device Reset Timers”. The first timer is the Power-up Timer (PWRT), which provides a fixed delay on power-up (parameter 33, Table 28-12). It is enabled by clearing (= 0) the PWRTEN Configuration bit. The second timer is the Oscillator Start-up Timer (OST), intended to keep the chip in Reset until the crystal oscillator is stable (XT and HS modes). The OST does this by counting 1024 oscillator cycles before allowing the oscillator to clock the device. When the HSPLL Oscillator mode is selected, the device is kept in Reset for an additional 2 ms following the HS mode OST delay, so the PLL can lock to the incoming clock frequency. There is a delay of interval, TCSD (parameter 38, Table 28-12), following POR, while the controller becomes ready to execute instructions. This delay runs concurrently with any other delays. This may be the only delay that occurs when any of the EC or internal oscillator modes are used as the primary clock source. TABLE 2-4: OSC1 AND OSC2 PIN STATES IN SLEEP MODE Oscillator Mode OSC1 Pin OSC2 Pin INTCKO Floating, pulled by external clock At logic low (clock/4 output) INTIO Floating, pulled by external clock Configured as PORTA, bit 6 ECIO, ECPIO Floating, pulled by external clock Configured as PORTA, bit 6 EC Floating, pulled by external clock At logic low (clock/4 output) XT and HS Feedback inverter disabled at quiescent voltage level Feedback inverter disabled at quiescent voltage level Note: See Table 4-2 in Section 4.0 “Reset” for time-outs due to Sleep and MCLR Reset. © 2009 Microchip Technology Inc. DS39632E-page 35 PIC18F2455/2550/4455/4550 3.0 POWER-MANAGED MODES PIC18F2455/2550/4455/4550 devices offer a total of seven operating modes for more efficient power management. These modes provide a variety of options for selective power conservation in applications where resources may be limited (i.e., battery-powered devices). There are three categories of power-managed modes: • Run modes • Idle modes • Sleep mode These categories define which portions of the device are clocked and sometimes, what speed. The Run and Idle modes may use any of the three available clock sources (primary, secondary or internal oscillator block); the Sleep mode does not use a clock source. The power-managed modes include several power-saving features offered on previous PIC® devices. One is the clock switching feature, offered in other PIC18 devices, allowing the controller to use the Timer1 oscillator in place of the primary oscillator. Also included is the Sleep mode, offered by all PIC devices, where all device clocks are stopped. 3.1 Selecting Power-Managed Modes Selecting a power-managed mode requires two decisions: if the CPU is to be clocked or not and the selection of a clock source. The IDLEN bit (OSCCON<7>) controls CPU clocking, while the SCS1:SCS0 bits (OSCCON<1:0>) select the clock source. The individual modes, bit settings, clock sources and affected modules are summarized in Table 3-1. 3.1.1 CLOCK SOURCES The SCS1:SCS0 bits allow the selection of one of three clock sources for power-managed modes. They are: • The primary clock, as defined by the FOSC3:FOSC0 Configuration bits • The secondary clock (the Timer1 oscillator) • The internal oscillator block (for RC modes) 3.1.2 ENTERING POWER-MANAGED MODES Switching from one power-managed mode to another begins by loading the OSCCON register. The SCS1:SCS0 bits select the clock source and determine which Run or Idle mode is to be used. Changing these bits causes an immediate switch to the new clock source, assuming that it is running. The switch may also be subject to clock transition delays. These are discussed in Section 3.1.3 “Clock Transitions and Status Indicators” and subsequent sections. Entry to the power-managed Idle or Sleep modes is triggered by the execution of a SLEEP instruction. The actual mode that results depends on the status of the IDLEN bit. Depending on the current mode and the mode being switched to, a change to a power-managed mode does not always require setting all of these bits. Many transitions may be done by changing the oscillator select bits, or changing the IDLEN bit, prior to issuing a SLEEP instruction. If the IDLEN bit is already configured correctly, it may only be necessary to perform a SLEEP instruction to switch to the desired mode. TABLE 3-1: POWER-MANAGED MODES Mode OSCCON<7,1:0> Module Clocking Available Clock and Oscillator Source IDLEN(1) SCS1:SCS0 CPU Peripherals Sleep 0 N/A Off Off None – all clocks are disabled PRI_RUN N/A 00 Clocked Clocked Primary – all oscillator modes. This is the normal full-power execution mode. SEC_RUN N/A 01 Clocked Clocked Secondary – Timer1 oscillator RC_RUN N/A 1x Clocked Clocked Internal oscillator block(2) PRI_IDLE 1 00 Off Clocked Primary – all oscillator modes SEC_IDLE 1 01 Off Clocked Secondary – Timer1 oscillator RC_IDLE 1 1x Off Clocked Internal oscillator block(2) Note 1: IDLEN reflects its value when the SLEEP instruction is executed. 2: Includes INTOSC and INTOSC postscaler, as well as the INTRC source. PIC18F2455/2550/4455/4550 DS39632E-page 36 © 2009 Microchip Technology Inc. 3.1.3 CLOCK TRANSITIONS AND STATUS INDICATORS The length of the transition between clock sources is the sum of two cycles of the old clock source and three to four cycles of the new clock source. This formula assumes that the new clock source is stable. Three bits indicate the current clock source and its status. They are: • OSTS (OSCCON<3>) • IOFS (OSCCON<2>) • T1RUN (T1CON<6>) In general, only one of these bits will be set while in a given power-managed mode. When the OSTS bit is set, the primary clock is providing the device clock. When the IOFS bit is set, the INTOSC output is providing a stable, 8 MHz clock source to a divider that actually drives the device clock. When the T1RUN bit is set, the Timer1 oscillator is providing the clock. If none of these bits are set, then either the INTRC clock source is clocking the device, or the INTOSC source is not yet stable. If the internal oscillator block is configured as the primary clock source by the FOSC3:FOSC0 Configuration bits, then both the OSTS and IOFS bits may be set when in PRI_RUN or PRI_IDLE modes. This indicates that the primary clock (INTOSC output) is generating a stable 8 MHz output. Entering another power-managed RC mode at the same frequency would clear the OSTS bit. 3.1.4 MULTIPLE SLEEP COMMANDS The power-managed mode that is invoked with the SLEEP instruction is determined by the setting of the IDLEN bit at the time the instruction is executed. If another SLEEP instruction is executed, the device will enter the power-managed mode specified by IDLEN at that time. If IDLEN has changed, the device will enter the new power-managed mode specified by the new setting. Upon resuming normal operation after waking from Sleep or Idle, the internal state machines require at least one TCY delay before another SLEEP instruction can be executed. If two back to back SLEEP instructions will be executed, the process shown in Example 3-1 should be used. EXAMPLE 3-1: EXECUTING BACK TO BACK SLEEP INSTRUCTIONS 3.2 Run Modes In the Run modes, clocks to both the core and peripherals are active. The difference between these modes is the clock source. 3.2.1 PRI_RUN MODE The PRI_RUN mode is the normal, full-power execution mode of the microcontroller. This is also the default mode upon a device Reset unless Two-Speed Start-up is enabled (see Section 25.3 “Two-Speed Start-up” for details). In this mode, the OSTS bit is set. The IOFS bit may be set if the internal oscillator block is the primary clock source (see Section 2.4.1 “Oscillator Control Register”). 3.2.2 SEC_RUN MODE The SEC_RUN mode is the compatible mode to the “clock switching” feature offered in other PIC18 devices. In this mode, the CPU and peripherals are clocked from the Timer1 oscillator. This gives users the option of lower power consumption while still using a high-accuracy clock source. Note 1: Caution should be used when modifying a single IRCF bit. If VDD is less than 3V, it is possible to select a higher clock speed than is supported by the low VDD. Improper device operation may result if the VDD/FOSC specifications are violated. 2: Executing a SLEEP instruction does not necessarily place the device into Sleep mode. It acts as the trigger to place the controller into either the Sleep mode, or one of the Idle modes, depending on the setting of the IDLEN bit. SLEEP NOP ;Wait at least 1 Tcy before executing another sleep instruction SLEEP © 2009 Microchip Technology Inc. DS39632E-page 37 PIC18F2455/2550/4455/4550 SEC_RUN mode is entered by setting the SCS1:SCS0 bits to ‘01’. The device clock source is switched to the Timer1 oscillator (see Figure 3-1), the primary oscillator is shut down, the T1RUN bit (T1CON<6>) is set and the OSTS bit is cleared. On transitions from SEC_RUN mode to PRI_RUN, the peripherals and CPU continue to be clocked from the Timer1 oscillator while the primary clock is started. When the primary clock becomes ready, a clock switch back to the primary clock occurs (see Figure 3-2). When the clock switch is complete, the T1RUN bit is cleared, the OSTS bit is set and the primary clock is providing the clock. The IDLEN and SCS bits are not affected by the wake-up; the Timer1 oscillator continues to run. FIGURE 3-1: TRANSITION TIMING FOR ENTRY TO SEC_RUN MODE FIGURE 3-2: TRANSITION TIMING FROM SEC_RUN MODE TO PRI_RUN MODE (HSPLL) Note: The Timer1 oscillator should already be running prior to entering SEC_RUN mode. If the T1OSCEN bit is not set when the SCS1:SCS0 bits are set to ‘01’, entry to SEC_RUN mode will not occur. If the Timer1 oscillator is enabled but not yet running, device clocks will be delayed until the oscillator has started. In such situations, initial oscillator operation is far from stable and unpredictable operation may result. Q2 Q3 Q4 OSC1 Peripheral Program Q1 T1OSI Q1 Counter Clock CPU Clock PC PC + 2 1 2 3 n-1 n Clock Transition(1) Q2 Q3 Q4 Q1 Q2 Q3 PC + 4 Note 1: Clock transition typically occurs within 2-4 TOSC. Q1 Q3 Q4 OSC1 Peripheral Program PC T1OSI PLL Clock Q1 PC + 4 Q2 Output Q3 Q4 Q1 CPU Clock PC + 2 Clock Counter Q2 Q2 Q3 Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale. 2: Clock transition typically occurs within 2-4 TOSC. SCS1:SCS0 bits Changed TPLL(1) 1 2 n-1 n Clock(2) OSTS bit Set Transition TOST(1) PIC18F2455/2550/4455/4550 DS39632E-page 38 © 2009 Microchip Technology Inc. 3.2.3 RC_RUN MODE In RC_RUN mode, the CPU and peripherals are clocked from the internal oscillator block using the INTOSC multiplexer; the primary clock is shut down. When using the INTRC source, this mode provides the best power conservation of all the Run modes while still executing code. It works well for user applications which are not highly timing sensitive or do not require high-speed clocks at all times. If the primary clock source is the internal oscillator block (either INTRC or INTOSC), there are no distinguishable differences between the PRI_RUN and RC_RUN modes during execution. However, a clock switch delay will occur during entry to and exit from RC_RUN mode. Therefore, if the primary clock source is the internal oscillator block, the use of RC_RUN mode is not recommended. This mode is entered by setting SCS1 to ‘1’. Although it is ignored, it is recommended that SCS0 also be cleared; this is to maintain software compatibility with future devices. When the clock source is switched to the INTOSC multiplexer (see Figure 3-3), the primary oscillator is shut down and the OSTS bit is cleared. The IRCF bits may be modified at any time to immediately change the clock speed. If the IRCF bits and the INTSRC bit are all clear, the INTOSC output is not enabled and the IOFS bit will remain clear; there will be no indication of the current clock source. The INTRC source is providing the device clocks. If the IRCF bits are changed from all clear (thus, enabling the INTOSC output), or if INTSRC is set, the IOFS bit becomes set after the INTOSC output becomes stable. Clocks to the device continue while the INTOSC source stabilizes after an interval of TIOBST. If the IRCF bits were previously at a non-zero value or if INTSRC was set before setting SCS1 and the INTOSC source was already stable, the IOFS bit will remain set. On transitions from RC_RUN mode to PRI_RUN mode, the device continues to be clocked from the INTOSC multiplexer while the primary clock is started. When the primary clock becomes ready, a clock switch to the primary clock occurs (see Figure 3-4). When the clock switch is complete, the IOFS bit is cleared, the OSTS bit is set and the primary clock is providing the device clock. The IDLEN and SCS bits are not affected by the switch. The INTRC source will continue to run if either the WDT or the Fail-Safe Clock Monitor is enabled. Note: Caution should be used when modifying a single IRCF bit. If VDD is less than 3V, it is possible to select a higher clock speed than is supported by the low VDD. Improper device operation may result if the VDD/FOSC specifications are violated. © 2009 Microchip Technology Inc. DS39632E-page 39 PIC18F2455/2550/4455/4550 FIGURE 3-3: TRANSITION TIMING TO RC_RUN MODE FIGURE 3-4: TRANSITION TIMING FROM RC_RUN MODE TO PRI_RUN MODE Q2 Q3 Q4 OSC1 Peripheral Program Q1 INTRC Q1 Counter Clock CPU Clock PC PC + 2 1 2 3 n-1 n Clock Transition(1) Q2 Q3 Q4 Q1 Q2 Q3 PC + 4 Note 1: Clock transition typically occurs within 2-4 TOSC. Q1 Q3 Q4 OSC1 Peripheral Program PC INTOSC PLL Clock Q1 PC + 4 Q2 Output Q3 Q4 Q1 CPU Clock PC + 2 Clock Counter Q2 Q2 Q3 Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale. 2: Clock transition typically occurs within 2-4 TOSC. SCS1:SCS0 bits Changed TPLL(1) 1 2 n-1 n Clock(2) OSTS bit Set Transition Multiplexer TOST(1) PIC18F2455/2550/4455/4550 DS39632E-page 40 © 2009 Microchip Technology Inc. 3.3 Sleep Mode The power-managed Sleep mode in the PIC18F2455/2550/4455/4550 devices is identical to the legacy Sleep mode offered in all other PIC devices. It is entered by clearing the IDLEN bit (the default state on device Reset) and executing the SLEEP instruction. This shuts down the selected oscillator (Figure 3-5). All clock source status bits are cleared. Entering the Sleep mode from any other mode does not require a clock switch. This is because no clocks are needed once the controller has entered Sleep. If the WDT is selected, the INTRC source will continue to operate. If the Timer1 oscillator is enabled, it will also continue to run. When a wake event occurs in Sleep mode (by interrupt, Reset or WDT time-out), the device will not be clocked until the clock source selected by the SCS1:SCS0 bits becomes ready (see Figure 3-6), or it will be clocked from the internal oscillator block if either the Two-Speed Start-up or the Fail-Safe Clock Monitor are enabled (see Section 25.0 “Special Features of the CPU”). In either case, the OSTS bit is set when the primary clock is providing the device clocks. The IDLEN and SCS bits are not affected by the wake-up. 3.4 Idle Modes The Idle modes allow the controller’s CPU to be selectively shut down while the peripherals continue to operate. Selecting a particular Idle mode allows users to further manage power consumption. If the IDLEN bit is set to ‘1’ when a SLEEP instruction is executed, the peripherals will be clocked from the clock source selected using the SCS1:SCS0 bits; however, the CPU will not be clocked. The clock source status bits are not affected. Setting IDLEN and executing a SLEEP instruction provides a quick method of switching from a given Run mode to its corresponding Idle mode. If the WDT is selected, the INTRC source will continue to operate. If the Timer1 oscillator is enabled, it will also continue to run. Since the CPU is not executing instructions, the only exits from any of the Idle modes are by interrupt, WDT time-out or a Reset. When a wake event occurs, CPU execution is delayed by an interval of TCSD (parameter 38, Table 28-12) while it becomes ready to execute code. When the CPU begins executing code, it resumes with the same clock source for the current Idle mode. For example, when waking from RC_IDLE mode, the internal oscillator block will clock the CPU and peripherals (in other words, RC_RUN mode). The IDLEN and SCS bits are not affected by the wake-up. While in any Idle mode or Sleep mode, a WDT time-out will result in a WDT wake-up to the Run mode currently specified by the SCS1:SCS0 bits. FIGURE 3-5: TRANSITION TIMING FOR ENTRY TO SLEEP MODE FIGURE 3-6: TRANSITION TIMING FOR WAKE FROM SLEEP (HSPLL) Q2 Q3 Q4 OSC1 Peripheral Sleep Program Q1 Q1 Counter Clock CPU Clock PC PC + 2 Q3 Q4 Q1 Q2 OSC1 Peripheral Program PC PLL Clock Q3 Q4 Output CPU Clock Q1 Q2 Q3 Q4 Q1 Q2 Clock Counter PC + 4 PC + 6 Q1 Q2 Q3 Q4 Wake Event Note1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale. TOST(1) TPLL(1) OSTS bit Set PC + 2 © 2009 Microchip Technology Inc. DS39632E-page 41 PIC18F2455/2550/4455/4550 3.4.1 PRI_IDLE MODE This mode is unique among the three low-power Idle modes in that it does not disable the primary device clock. For timing sensitive applications, this allows for the fastest resumption of device operation, with its more accurate primary clock source, since the clock source does not have to “warm up” or transition from another oscillator. PRI_IDLE mode is entered from PRI_RUN mode by setting the IDLEN bit and executing a SLEEP instruction. If the device is in another Run mode, set IDLEN first, then clear the SCS bits and execute SLEEP. Although the CPU is disabled, the peripherals continue to be clocked from the primary clock source specified by the FOSC3:FOSC0 Configuration bits. The OSTS bit remains set (see Figure 3-7). When a wake event occurs, the CPU is clocked from the primary clock source. A delay of interval TCSD is required between the wake event and when code execution starts. This is required to allow the CPU to become ready to execute instructions. After the wake-up, the OSTS bit remains set. The IDLEN and SCS bits are not affected by the wake-up (see Figure 3-8). 3.4.2 SEC_IDLE MODE In SEC_IDLE mode, the CPU is disabled but the peripherals continue to be clocked from the Timer1 oscillator. This mode is entered from SEC_RUN by setting the IDLEN bit and executing a SLEEP instruction. If the device is in another Run mode, set IDLEN first, then set SCS1:SCS0 to ‘01’ and execute SLEEP. When the clock source is switched to the Timer1 oscillator, the primary oscillator is shut down, the OSTS bit is cleared and the T1RUN bit is set. When a wake event occurs, the peripherals continue to be clocked from the Timer1 oscillator. After an interval of TCSD following the wake event, the CPU begins executing code being clocked by the Timer1 oscillator. The IDLEN and SCS bits are not affected by the wake-up; the Timer1 oscillator continues to run (see Figure 3-8). FIGURE 3-7: TRANSITION TIMING FOR ENTRY TO IDLE MODE FIGURE 3-8: TRANSITION TIMING FOR WAKE FROM IDLE TO RUN MODE Note: The Timer1 oscillator should already be running prior to entering SEC_IDLE mode. If the T1OSCEN bit is not set when the SLEEP instruction is executed, the SLEEP instruction will be ignored and entry to SEC_IDLE mode will not occur. If the Timer1 oscillator is enabled but not yet running, peripheral clocks will be delayed until the oscillator has started. In such situations, initial oscillator operation is far from stable and unpredictable operation may result. Q1 Peripheral Program PC PC + 2 OSC1 Q3 Q4 Q1 CPU Clock Clock Counter Q2 OSC1 Peripheral Program PC CPU Clock Q1 Q3 Q4 Clock Counter Q2 Wake Event TCSD PIC18F2455/2550/4455/4550 DS39632E-page 42 © 2009 Microchip Technology Inc. 3.4.3 RC_IDLE MODE In RC_IDLE mode, the CPU is disabled but the peripherals continue to be clocked from the internal oscillator block using the INTOSC multiplexer. This mode allows for controllable power conservation during Idle periods. From RC_RUN, this mode is entered by setting the IDLEN bit and executing a SLEEP instruction. If the device is in another Run mode, first set IDLEN, then set the SCS1 bit and execute SLEEP. Although its value is ignored, it is recommended that SCS0 also be cleared; this is to maintain software compatibility with future devices. The INTOSC multiplexer may be used to select a higher clock frequency by modifying the IRCF bits before executing the SLEEP instruction. When the clock source is switched to the INTOSC multiplexer, the primary oscillator is shut down and the OSTS bit is cleared. If the IRCF bits are set to any non-zero value, or the INTSRC bit is set, the INTOSC output is enabled. The IOFS bit becomes set after the INTOSC output becomes stable, after an interval of TIOBST (parameter 39, Table 28-12). Clocks to the peripherals continue while the INTOSC source stabilizes. If the IRCF bits were previously at a non-zero value, or INTSRC was set before the SLEEP instruction was executed and the INTOSC source was already stable, the IOFS bit will remain set. If the IRCF bits and INTSRC are all clear, the INTOSC output will not be enabled, the IOFS bit will remain clear and there will be no indication of the current clock source. When a wake event occurs, the peripherals continue to be clocked from the INTOSC multiplexer. After a delay of TCSD following the wake event, the CPU begins executing code being clocked by the INTOSC multiplexer. The IDLEN and SCS bits are not affected by the wake-up. The INTRC source will continue to run if either the WDT or the Fail-Safe Clock Monitor is enabled. 3.5 Exiting Idle and Sleep Modes An exit from Sleep mode or any of the Idle modes is triggered by an interrupt, a Reset or a WDT time-out. This section discusses the triggers that cause exits from power-managed modes. The clocking subsystem actions are discussed in each of the power-managed modes (see Section 3.2 “Run Modes”, Section 3.3 “Sleep Mode” and Section 3.4 “Idle Modes”). 3.5.1 EXIT BY INTERRUPT Any of the available interrupt sources can cause the device to exit from an Idle mode or Sleep mode to a Run mode. To enable this functionality, an interrupt source must be enabled by setting its enable bit in one of the INTCON or PIE registers. The exit sequence is initiated when the corresponding interrupt flag bit is set. On all exits from Idle or Sleep modes by interrupt, code execution branches to the interrupt vector if the GIE/GIEH bit (INTCON<7>) is set. Otherwise, code execution continues or resumes without branching (see Section 9.0 “Interrupts”). A fixed delay of interval TCSD following the wake event is required when leaving Sleep and Idle modes. This delay is required for the CPU to prepare for execution. Instruction execution resumes on the first clock cycle following this delay. 3.5.2 EXIT BY WDT TIME-OUT A WDT time-out will cause different actions depending on which power-managed mode the device is in when the time-out occurs. If the device is not executing code (all Idle modes and Sleep mode), the time-out will result in an exit from the power-managed mode (see Section 3.2 “Run Modes” and Section 3.3 “Sleep Mode”). If the device is executing code (all Run modes), the time-out will result in a WDT Reset (see Section 25.2 “Watchdog Timer (WDT)”). The WDT timer and postscaler are cleared by executing a SLEEP or CLRWDT instruction, the loss of a currently selected clock source (if the Fail-Safe Clock Monitor is enabled) and modifying the IRCF bits in the OSCCON register if the internal oscillator block is the device clock source. 3.5.3 EXIT BY RESET Normally, the device is held in Reset by the Oscillator Start-up Timer (OST) until the primary clock becomes ready. At that time, the OSTS bit is set and the device begins executing code. If the internal oscillator block is the new clock source, the IOFS bit is set instead. The exit delay time from Reset to the start of code execution depends on both the clock sources before and after the wake-up and the type of oscillator if the new clock source is the primary clock. Exit delays are summarized in Table 3-2. Code execution can begin before the primary clock becomes ready. If either the Two-Speed Start-up (see Section 25.3 “Two-Speed Start-up”) or Fail-Safe Clock Monitor (see Section 25.4 “Fail-Safe Clock Monitor”) is enabled, the device may begin execution as soon as the Reset source has cleared. Execution is clocked by the INTOSC multiplexer driven by the internal oscillator block. Execution is clocked by the internal oscillator block until either the primary clock becomes ready or a power-managed mode is entered before the primary clock becomes ready; the primary clock is then shut down. © 2009 Microchip Technology Inc. DS39632E-page 43 PIC18F2455/2550/4455/4550 3.5.4 EXIT WITHOUT AN OSCILLATOR START-UP DELAY Certain exits from power-managed modes do not invoke the OST at all. There are two cases: • PRI_IDLE mode, where the primary clock source is not stopped; and • the primary clock source is not any of the XT or HS modes. In these instances, the primary clock source either does not require an oscillator start-up delay, since it is already running (PRI_IDLE), or normally does not require an oscillator start-up delay (EC and any internal oscillator modes). However, a fixed delay of interval TCSD following the wake event is still required when leaving Sleep and Idle modes to allow the CPU to prepare for execution. Instruction execution resumes on the first clock cycle following this delay. TABLE 3-2: EXIT DELAY ON WAKE-UP BY RESET FROM SLEEP MODE OR ANY IDLE MODE (BY CLOCK SOURCES) Microcontroller Clock Source Exit Delay Clock Ready Status Before Wake-up After Wake-up Bit (OSCCON) Primary Device Clock (PRI_IDLE mode) XT, HS None XTPLL, HSPLL OSTS EC INTOSC(3) IOFS T1OSC or INTRC(1) XT, HS TOST(4) XTPLL, HSPLL TOST + trc OSTS (4) EC TCSD(2) INTOSC(3) TIOBST(5) IOFS INTOSC(3) XT, HS TOST(4) XTPLL, HSPLL TOST + trc OSTS (4) EC TCSD(2) INTOSC(3) None IOFS None (Sleep mode) XT, HS TOST(4) XTPLL, HSPLL TOST + trc OSTS (4) EC TCSD(2) INTOSC(3) TIOBST(5) IOFS Note 1: In this instance, refers specifically to the 31 kHz INTRC clock source. 2: TCSD (parameter 38, Table 28-12) is a required delay when waking from Sleep and all Idle modes and runs concurrently with any other required delays (see Section 3.4 “Idle Modes”). 3: Includes both the INTOSC 8 MHz source and postscaler derived frequencies. 4: TOST is the Oscillator Start-up Timer period (parameter 32, Table 28-12). trc is the PLL lock time-out (parameter F12, Table 28-9); it is also designated as TPLL. 5: Execution continues during TIOBST (parameter 39, Table 28-12), the INTOSC stabilization period. PIC18F2455/2550/4455/4550 DS39632E-page 44 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 45 PIC18F2455/2550/4455/4550 4.0 RESET The PIC18F2455/2550/4455/4550 devices differentiate between various kinds of Reset: a) Power-on Reset (POR) b) MCLR Reset during normal operation c) MCLR Reset during power-managed modes d) Watchdog Timer (WDT) Reset (during execution) e) Programmable Brown-out Reset (BOR) f) RESET Instruction g) Stack Full Reset h) Stack Underflow Reset This section discusses Resets generated by MCLR, POR and BOR and covers the operation of the various start-up timers. Stack Reset events are covered in Section 5.1.2.4 “Stack Full and Underflow Resets”. WDT Resets are covered in Section 25.2 “Watchdog Timer (WDT)”. A simplified block diagram of the on-chip Reset circuit is shown in Figure 4-1. 4.1 RCON Register Device Reset events are tracked through the RCON register (Register 4-1). The lower five bits of the register indicate that a specific Reset event has occurred. In most cases, these bits can only be cleared by the event and must be set by the application after the event. The state of these flag bits, taken together, can be read to indicate the type of Reset that just occurred. This is described in more detail in Section 4.6 “Reset State of Registers”. The RCON register also has control bits for setting interrupt priority (IPEN) and software control of the BOR (SBOREN). Interrupt priority is discussed in Section 9.0 “Interrupts”. BOR is covered in Section 4.4 “Brown-out Reset (BOR)”. FIGURE 4-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT S R Q External Reset MCLR VDD OSC1 WDT Time-out VDD Rise Detect OST/PWRT INTRC(1) POR Pulse OST 10-Bit Ripple Counter PWRT Chip_Reset 11-Bit Ripple Counter Enable OST(2) Enable PWRT Note 1: This is the low-frequency INTRC source from the internal oscillator block. 2: See Table 4-2 for time-out situations. Brown-out Reset BOREN RESET Instruction Stack Pointer Stack Full/Underflow Reset Sleep ( )_IDLE 1024 Cycles 32 μs 65.5 ms MCLRE PIC18F2455/2550/4455/4550 DS39632E-page 46 © 2009 Microchip Technology Inc. REGISTER 4-1: RCON: RESET CONTROL REGISTER R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0 IPEN SBOREN — RI TO PD POR BOR bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 IPEN: Interrupt Priority Enable bit 1 = Enable priority levels on interrupts 0 = Disable priority levels on interrupts (PIC16CXXX Compatibility mode) bit 6 SBOREN: BOR Software Enable bit(1) If BOREN1:BOREN0 = 01: 1 = BOR is enabled 0 = BOR is disabled If BOREN1:BOREN0 = 00, 10 or 11: Bit is disabled and read as ‘0’. bit 5 Unimplemented: Read as ‘0’ bit 4 RI: RESET Instruction Flag bit 1 = The RESET instruction was not executed (set by firmware only) 0 = The RESET instruction was executed causing a device Reset (must be set in software after a Brown-out Reset occurs) bit 3 TO: Watchdog Time-out Flag bit 1 = Set by power-up, CLRWDT instruction or SLEEP instruction 0 = A WDT time-out occurred bit 2 PD: Power-Down Detection Flag bit 1 = Set by power-up or by the CLRWDT instruction 0 = Set by execution of the SLEEP instruction bit 1 POR: Power-on Reset Status bit(2) 1 = A Power-on Reset has not occurred (set by firmware only) 0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs) bit 0 BOR: Brown-out Reset Status bit 1 = A Brown-out Reset has not occurred (set by firmware only) 0 = A Brown-out Reset occurred (must be set in software after a Brown-out Reset occurs) Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’. 2: The actual Reset value of POR is determined by the type of device Reset. See the notes following this register and Section 4.6 “Reset State of Registers” for additional information. Note 1: It is recommended that the POR bit be set after a Power-on Reset has been detected so that subsequent Power-on Resets may be detected. 2: Brown-out Reset is said to have occurred when BOR is ‘0’ and POR is ‘1’ (assuming that POR was set to ‘1’ by software immediately after POR). © 2009 Microchip Technology Inc. DS39632E-page 47 PIC18F2455/2550/4455/4550 4.2 Master Clear Reset (MCLR) The MCLR pin provides a method for triggering an external Reset of the device. A Reset is generated by holding the pin low. These devices have a noise filter in the MCLR Reset path which detects and ignores small pulses. The MCLR pin is not driven low by any internal Resets, including the WDT. In PIC18F2455/2550/4455/4550 devices, the MCLR input can be disabled with the MCLRE Configuration bit. When MCLR is disabled, the pin becomes a digital input. See Section 10.5 “PORTE, TRISE and LATE Registers” for more information. 4.3 Power-on Reset (POR) A Power-on Reset pulse is generated on-chip whenever VDD rises above a certain threshold. This allows the device to start in the initialized state when VDD is adequate for operation. To take advantage of the POR circuitry, tie the MCLR pin through a resistor (1 kΩ to 10 kΩ) to VDD. This will eliminate external RC components usually needed to create a Power-on Reset delay. A minimum rise rate for VDD is specified (parameter D004, Section 28.1 “DC Characteristics”). For a slow rise time, see Figure 4-2. When the device starts normal operation (i.e., exits the Reset condition), device operating parameters (voltage, frequency, temperature, etc.) must be met to ensure operation. If these conditions are not met, the device must be held in Reset until the operating conditions are met. POR events are captured by the POR bit (RCON<1>). The state of the bit is set to ‘0’ whenever a POR occurs; it does not change for any other Reset event. POR is not reset to ‘1’ by any hardware event. To capture multiple events, the user manually resets the bit to ‘1’ in software following any POR. FIGURE 4-2: EXTERNAL POWER-ON RESET CIRCUIT (FOR SLOW VDD POWER-UP) Note 1: External Power-on Reset circuit is required only if the VDD power-up slope is too slow. The diode D helps discharge the capacitor quickly when VDD powers down. 2: R < 40 kΩ is recommended to make sure that the voltage drop across R does not violate the device’s electrical specification. 3: R1 ≥ 1 kΩ will limit any current flowing into MCLR from external capacitor C, in the event of MCLR/VPP pin breakdown, due to Electrostatic Discharge (ESD) or Electrical Overstress (EOS). C R1 D R VDD MCLR PIC18FXXXX VDD PIC18F2455/2550/4455/4550 DS39632E-page 48 © 2009 Microchip Technology Inc. 4.4 Brown-out Reset (BOR) PIC18F2455/2550/4455/4550 devices implement a BOR circuit that provides the user with a number of configuration and power-saving options. The BOR is controlled by the BORV1:BORV0 and BOREN1:BOREN0 Configuration bits. There are a total of four BOR configurations which are summarized in Table 4-1. The BOR threshold is set by the BORV1:BORV0 bits. If BOR is enabled (any values of BOREN1:BOREN0 except ‘00’), any drop of VDD below VBOR (parameter D005, Section 28.1 “DC Characteristics”) for greater than TBOR (parameter 35, Table 28-12) will reset the device. A Reset may or may not occur if VDD falls below VBOR for less than TBOR. The chip will remain in Brown-out Reset until VDD rises above VBOR. If the Power-up Timer is enabled, it will be invoked after VDD rises above VBOR; it then will keep the chip in Reset for an additional time delay, TPWRT (parameter 33, Table 28-12). If VDD drops below VBOR while the Power-up Timer is running, the chip will go back into a Brown-out Reset and the Power-up Timer will be initialized. Once VDD rises above VBOR, the Power-up Timer will execute the additional time delay. BOR and the Power-on Timer (PWRT) are independently configured. Enabling BOR Reset does not automatically enable the PWRT. 4.4.1 SOFTWARE ENABLED BOR When BOREN1:BOREN0 = 01, the BOR can be enabled or disabled by the user in software. This is done with the control bit, SBOREN (RCON<6>). Setting SBOREN enables the BOR to function as previously described. Clearing SBOREN disables the BOR entirely. The SBOREN bit operates only in this mode; otherwise, it is read as ‘0’. Placing the BOR under software control gives the user the additional flexibility of tailoring the application to its environment without having to reprogram the device to change BOR configuration. It also allows the user to tailor device power consumption in software by eliminating the incremental current that the BOR consumes. While the BOR current is typically very small, it may have some impact in low-power applications. 4.4.2 DETECTING BOR When BOR is enabled, the BOR bit always resets to ‘0’ on any BOR or POR event. This makes it difficult to determine if a BOR event has occurred just by reading the state of BOR alone. A more reliable method is to simultaneously check the state of both POR and BOR. This assumes that the POR bit is reset to ‘1’ in software immediately after any POR event. IF BOR is ‘0’ while POR is ‘1’, it can be reliably assumed that a BOR event has occurred. 4.4.3 DISABLING BOR IN SLEEP MODE When BOREN1:BOREN0 = 10, the BOR remains under hardware control and operates as previously described. Whenever the device enters Sleep mode, however, the BOR is automatically disabled. When the device returns to any other operating mode, BOR is automatically re-enabled. This mode allows for applications to recover from brown-out situations, while actively executing code, when the device requires BOR protection the most. At the same time, it saves additional power in Sleep mode by eliminating the small incremental BOR current. TABLE 4-1: BOR CONFIGURATIONS Note: Even when BOR is under software control, the BOR Reset voltage level is still set by the BORV1:BORV0 Configuration bits. It cannot be changed in software. BOR Configuration Status of SBOREN (RCON<6>) BOR Operation BOREN1 BOREN0 0 0 Unavailable BOR disabled; must be enabled by reprogramming the Configuration bits. 0 1 Available BOR enabled in software; operation controlled by SBOREN. 1 0 Unavailable BOR enabled in hardware in Run and Idle modes, disabled during Sleep mode. 1 1 Unavailable BOR enabled in hardware; must be disabled by reprogramming the Configuration bits. © 2009 Microchip Technology Inc. DS39632E-page 49 PIC18F2455/2550/4455/4550 4.5 Device Reset Timers PIC18F2455/2550/4455/4550 devices incorporate three separate on-chip timers that help regulate the Power-on Reset process. Their main function is to ensure that the device clock is stable before code is executed. These timers are: • Power-up Timer (PWRT) • Oscillator Start-up Timer (OST) • PLL Lock Time-out 4.5.1 POWER-UP TIMER (PWRT) The Power-up Timer (PWRT) of the PIC18F2455/2550/ 4455/4550 devices is an 11-bit counter which uses the INTRC source as the clock input. This yields an approximate time interval of 2048 x 32 μs = 65.6ms. While the PWRT is counting, the device is held in Reset. The power-up time delay depends on the INTRC clock and will vary from chip to chip due to temperature and process variation. See DC parameter 33 (Table 28-12) for details. The PWRT is enabled by clearing the PWRTEN Configuration bit. 4.5.2 OSCILLATOR START-UP TIMER (OST) The Oscillator Start-up Timer (OST) provides a 1024 oscillator cycle (from OSC1 input) delay after the PWRT delay is over (parameter 33, Table 28-12). This ensures that the crystal oscillator or resonator has started and stabilized. The OST time-out is invoked only for XT, HS and HSPLL modes and only on Power-on Reset or on exit from most power-managed modes. 4.5.3 PLL LOCK TIME-OUT With the PLL enabled in its PLL mode, the time-out sequence following a Power-on Reset is slightly different from other oscillator modes. A separate timer is used to provide a fixed time-out that is sufficient for the PLL to lock to the main oscillator frequency. This PLL lock time-out (TPLL) is typically 2 ms and follows the oscillator start-up time-out. 4.5.4 TIME-OUT SEQUENCE On power-up, the time-out sequence is as follows: 1. After the POR condition has cleared, PWRT time-out is invoked (if enabled). 2. Then, the OST is activated. The total time-out will vary based on oscillator configuration and the status of the PWRT. Figure 4-3, Figure 4-4, Figure 4-5, Figure 4-6 and Figure 4-7 all depict time-out sequences on power-up, with the Power-up Timer enabled and the device operating in HS Oscillator mode. Figures 4-3 through 4-6 also apply to devices operating in XT mode. For devices in RC mode and with the PWRT disabled, on the other hand, there will be no time-out at all. Since the time-outs occur from the POR pulse, if MCLR is kept low long enough, all time-outs will expire. Bringing MCLR high will begin execution immediately (Figure 4-5). This is useful for testing purposes or to synchronize more than one PIC18FXXXX device operating in parallel. TABLE 4-2: TIME-OUT IN VARIOUS SITUATIONS Oscillator Configuration Power-up(2) and Brown-out Exit from PWRTEN = 0 PWRTEN = 1 Power-Managed Mode HS, XT 66 ms(1) + 1024 TOSC 1024 TOSC 1024 TOSC HSPLL, XTPLL 66 ms(1) + 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2) EC, ECIO 66 ms(1) — — ECPLL, ECPIO 66 ms(1) + 2 ms(2) 2 ms(2) 2 ms(2) INTIO, INTCKO 66 ms(1) — — INTHS, INTXT 66 ms(1) + 1024 TOSC 1024 TOSC 1024 TOSC Note 1: 66 ms (65.5 ms) is the nominal Power-up Timer (PWRT) delay. 2: 2 ms is the nominal time required for the PLL to lock. PIC18F2455/2550/4455/4550 DS39632E-page 50 © 2009 Microchip Technology Inc. FIGURE 4-3: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD, VDD RISE < TPWRT) FIGURE 4-4: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1 FIGURE 4-5: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2 TPWRT TOST VDD MCLR INTERNAL POR PWRT TIME-OUT OST TIME-OUT INTERNAL RESET TPWRT TOST VDD MCLR INTERNAL POR PWRT TIME-OUT OST TIME-OUT INTERNAL RESET VDD MCLR INTERNAL POR PWRT TIME-OUT OST TIME-OUT INTERNAL RESET TPWRT TOST © 2009 Microchip Technology Inc. DS39632E-page 51 PIC18F2455/2550/4455/4550 FIGURE 4-6: SLOW RISE TIME (MCLR TIED TO VDD, VDD RISE > TPWRT) FIGURE 4-7: TIME-OUT SEQUENCE ON POR w/PLL ENABLED (MCLR TIED TO VDD) VDD MCLR INTERNAL POR PWRT TIME-OUT OST TIME-OUT INTERNAL RESET 0V 1V 5V TPWRT TOST TPWRT TOST VDD MCLR INTERNAL POR PWRT TIME-OUT OST TIME-OUT INTERNAL RESET PLL TIME-OUT TPLL Note: TOST = 1024 clock cycles. TPLL ≈ 2 ms max. First three stages of the Power-up Timer. PIC18F2455/2550/4455/4550 DS39632E-page 52 © 2009 Microchip Technology Inc. 4.6 Reset State of Registers Most registers are unaffected by a Reset. Their status is unknown on POR and unchanged by all other Resets. The other registers are forced to a “Reset state” depending on the type of Reset that occurred. Most registers are not affected by a WDT wake-up, since this is viewed as the resumption of normal operation. Status bits from the RCON register, RI, TO, PD, POR and BOR, are set or cleared differently in different Reset situations as indicated in Table 4-3. These bits are used in software to determine the nature of the Reset. Table 4-4 describes the Reset states for all of the Special Function Registers. These are categorized by Power-on and Brown-out Resets, Master Clear and WDT Resets and WDT wake-ups. TABLE 4-3: STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION FOR RCON REGISTER Condition Program Counter RCON Register STKPTR Register RI TO PD POR BOR STKFUL STKUNF Power-on Reset 0000h 1 1 1 0 0 0 0 RESET instruction 0000h 0 u u u u u u Brown-out Reset 0000h 1 1 1 u 0 u u MCLR Reset during power-managed Run modes 0000h u 1 u u u u u MCLR Reset during power-managed Idle modes and Sleep mode 0000h u 1 0 u u u u WDT time-out during full power or power-managed Run modes 0000h u 0 u u u u u MCLR Reset during full-power execution 0000h u u u u u u u Stack Full Reset (STVREN = 1) 0000h u u u u u 1 u Stack Underflow Reset (STVREN = 1) 0000h u u u u u u 1 Stack Underflow Error (not an actual Reset, STVREN = 0) 0000h u u u u u u 1 WDT time-out during power-managed Idle or Sleep modes PC + 2 u 0 0 u u u u Interrupt exit from power-managed modes PC + 2(1) u u 0 u u u u Legend: u = unchanged Note 1: When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the interrupt vector (008h or 0018h). 2: Reset state is ‘1’ for POR and unchanged for all other Resets when software BOR is enabled (BOREN1:BOREN0 Configuration bits = 01 and SBOREN = 1); otherwise, the Reset state is ‘0’. © 2009 Microchip Technology Inc. DS39632E-page 53 PIC18F2455/2550/4455/4550 TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS Register Applicable Devices Power-on Reset, Brown-out Reset MCLR Resets, WDT Reset, RESET Instruction, Stack Resets Wake-up via WDT or Interrupt TOSU 2455 2550 4455 4550 ---0 0000 ---0 0000 ---0 uuuu(1) TOSH 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu(1) TOSL 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu(1) STKPTR 2455 2550 4455 4550 00-0 0000 uu-0 0000 uu-u uuuu(1) PCLATU 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu PCLATH 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu PCL 2455 2550 4455 4550 0000 0000 0000 0000 PC + 2(3) TBLPTRU 2455 2550 4455 4550 --00 0000 --00 0000 --uu uuuu TBLPTRH 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TBLPTRL 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TABLAT 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu PRODH 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu PRODL 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu INTCON 2455 2550 4455 4550 0000 000x 0000 000u uuuu uuuu(2) INTCON2 2455 2550 4455 4550 1111 -1-1 1111 -1-1 uuuu -u-u(2) INTCON3 2455 2550 4455 4550 11-0 0-00 11-0 0-00 uu-u u-uu(2) INDF0 2455 2550 4455 4550 N/A N/A N/A POSTINC0 2455 2550 4455 4550 N/A N/A N/A POSTDEC0 2455 2550 4455 4550 N/A N/A N/A PREINC0 2455 2550 4455 4550 N/A N/A N/A PLUSW0 2455 2550 4455 4550 N/A N/A N/A FSR0H 2455 2550 4455 4550 ---- 0000 ---- 0000 ---- uuuu FSR0L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu WREG 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu INDF1 2455 2550 4455 4550 N/A N/A N/A POSTINC1 2455 2550 4455 4550 N/A N/A N/A POSTDEC1 2455 2550 4455 4550 N/A N/A N/A PREINC1 2455 2550 4455 4550 N/A N/A N/A PLUSW1 2455 2550 4455 4550 N/A N/A N/A FSR1H 2455 2550 4455 4550 ---- 0000 ---- 0000 ---- uuuu FSR1L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu BSR 2455 2550 4455 4550 ---- 0000 ---- 0000 ---- uuuu Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition. Shaded cells indicate conditions do not apply for the designated device. Note 1: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack. 2: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up). 3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector (0008h or 0018h). 4: See Table 4-3 for Reset value for specific condition. 5: PORTA<6>, LATA<6> and TRISA<6> are enabled depending on the oscillator mode selected. When not enabled as PORTA pins, they are disabled and read ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 54 © 2009 Microchip Technology Inc. INDF2 2455 2550 4455 4550 N/A N/A N/A POSTINC2 2455 2550 4455 4550 N/A N/A N/A POSTDEC2 2455 2550 4455 4550 N/A N/A N/A PREINC2 2455 2550 4455 4550 N/A N/A N/A PLUSW2 2455 2550 4455 4550 N/A N/A N/A FSR2H 2455 2550 4455 4550 ---- 0000 ---- 0000 ---- uuuu FSR2L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu STATUS 2455 2550 4455 4550 ---x xxxx ---u uuuu ---u uuuu TMR0H 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TMR0L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu T0CON 2455 2550 4455 4550 1111 1111 1111 1111 uuuu uuuu OSCCON 2455 2550 4455 4550 0100 q000 0100 00q0 uuuu uuqu HLVDCON 2455 2550 4455 4550 0-00 0101 0-00 0101 u-uu uuuu WDTCON 2455 2550 4455 4550 ---- ---0 ---- ---0 ---- ---u RCON(4) 2455 2550 4455 4550 0q-1 11q0 0q-q qquu uq-u qquu TMR1H 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu TMR1L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu T1CON 2455 2550 4455 4550 0000 0000 u0uu uuuu uuuu uuuu TMR2 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu PR2 2455 2550 4455 4550 1111 1111 1111 1111 1111 1111 T2CON 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu SSPBUF 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu SSPADD 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu SSPSTAT 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu SSPCON1 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu SSPCON2 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu ADRESH 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu ADRESL 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu ADCON0 2455 2550 4455 4550 --00 0000 --00 0000 --uu uuuu ADCON1 2455 2550 4455 4550 --00 0qqq --00 0qqq --uu uuuu ADCON2 2455 2550 4455 4550 0-00 0000 0-00 0000 u-uu uuuu TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED) Register Applicable Devices Power-on Reset, Brown-out Reset MCLR Resets, WDT Reset, RESET Instruction, Stack Resets Wake-up via WDT or Interrupt Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition. Shaded cells indicate conditions do not apply for the designated device. Note 1: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack. 2: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up). 3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector (0008h or 0018h). 4: See Table 4-3 for Reset value for specific condition. 5: PORTA<6>, LATA<6> and TRISA<6> are enabled depending on the oscillator mode selected. When not enabled as PORTA pins, they are disabled and read ‘0’. © 2009 Microchip Technology Inc. DS39632E-page 55 PIC18F2455/2550/4455/4550 CCPR1H 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu CCPR1L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu CCP1CON 2455 2550 4455 4550 --00 0000 --00 0000 --uu uuuu 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu CCPR2H 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu CCPR2L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu CCP2CON 2455 2550 4455 4550 --00 0000 --00 0000 --uu uuuu BAUDCON 2455 2550 4455 4550 0100 0-00 0100 0-00 uuuu u-uu ECCP1DEL 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu ECCP1AS 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu CVRCON 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu CMCON 2455 2550 4455 4550 0000 0111 0000 0111 uuuu uuuu TMR3H 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu TMR3L 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu T3CON 2455 2550 4455 4550 0000 0000 uuuu uuuu uuuu uuuu SPBRGH 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu SPBRG 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu RCREG 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TXREG 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TXSTA 2455 2550 4455 4550 0000 0010 0000 0010 uuuu uuuu RCSTA 2455 2550 4455 4550 0000 000x 0000 000x uuuu uuuu EEADR 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu EEDATA 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu EECON2 2455 2550 4455 4550 0000 0000 0000 0000 0000 0000 EECON1 2455 2550 4455 4550 xx-0 x000 uu-0 u000 uu-0 u000 TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED) Register Applicable Devices Power-on Reset, Brown-out Reset MCLR Resets, WDT Reset, RESET Instruction, Stack Resets Wake-up via WDT or Interrupt Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition. Shaded cells indicate conditions do not apply for the designated device. Note 1: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack. 2: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up). 3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector (0008h or 0018h). 4: See Table 4-3 for Reset value for specific condition. 5: PORTA<6>, LATA<6> and TRISA<6> are enabled depending on the oscillator mode selected. When not enabled as PORTA pins, they are disabled and read ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 56 © 2009 Microchip Technology Inc. IPR2 2455 2550 4455 4550 1111 1111 1111 1111 uuuu uuuu PIR2 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu(2) PIE2 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu IPR1 2455 2550 4455 4550 1111 1111 1111 1111 uuuu uuuu 2455 2550 4455 4550 -111 1111 -111 1111 -uuu uuuu PIR1 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu(2) 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu PIE1 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu OSCTUNE 2455 2550 4455 4550 0--0 0000 0--0 0000 u--u uuuu TRISE 2455 2550 4455 4550 ---- -111 ---- -111 ---- -uuu TRISD 2455 2550 4455 4550 1111 1111 1111 1111 uuuu uuuu TRISC 2455 2550 4455 4550 11-- -111 11-- -111 uu-- -uuu TRISB 2455 2550 4455 4550 1111 1111 1111 1111 uuuu uuuu TRISA(5) 2455 2550 4455 4550 -111 1111(5) -111 1111(5) -uuu uuuu(5) LATE 2455 2550 4455 4550 ---- -xxx ---- -uuu ---- -uuu LATD 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu LATC 2455 2550 4455 4550 xx-- -xxx uu-- -uuu uu-- -uuu LATB 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu LATA(5) 2455 2550 4455 4550 -xxx xxxx(5) -uuu uuuu(5) -uuu uuuu(5) PORTE 2455 2550 4455 4550 0--- x000 0--- x000 u--- uuuu PORTD 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu PORTC 2455 2550 4455 4550 xxxx -xxx uuuu -uuu uuuu -uuu PORTB 2455 2550 4455 4550 xxxx xxxx uuuu uuuu uuuu uuuu PORTA(5) 2455 2550 4455 4550 -x0x 0000(5) -u0u 0000(5) -uuu uuuu(5) TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED) Register Applicable Devices Power-on Reset, Brown-out Reset MCLR Resets, WDT Reset, RESET Instruction, Stack Resets Wake-up via WDT or Interrupt Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition. Shaded cells indicate conditions do not apply for the designated device. Note 1: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack. 2: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up). 3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector (0008h or 0018h). 4: See Table 4-3 for Reset value for specific condition. 5: PORTA<6>, LATA<6> and TRISA<6> are enabled depending on the oscillator mode selected. When not enabled as PORTA pins, they are disabled and read ‘0’. © 2009 Microchip Technology Inc. DS39632E-page 57 PIC18F2455/2550/4455/4550 UEP15 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP14 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP13 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP12 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP11 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP10 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP9 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP8 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP7 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP6 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP5 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP4 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP3 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP2 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP1 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UEP0 2455 2550 4455 4550 ---0 0000 ---0 0000 ---u uuuu UCFG 2455 2550 4455 4550 00-0 0000 00-0 0000 uu-u uuuu UADDR 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu UCON 2455 2550 4455 4550 -0x0 000- -0x0 000- -uuu uuu- USTAT 2455 2550 4455 4550 -xxx xxx- -xxx xxx- -uuu uuu- UEIE 2455 2550 4455 4550 0--0 0000 0--0 0000 u--u uuuu UEIR 2455 2550 4455 4550 0--0 0000 0--0 0000 u--u uuuu UIE 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu UIR 2455 2550 4455 4550 -000 0000 -000 0000 -uuu uuuu UFRMH 2455 2550 4455 4550 ---- -xxx ---- -xxx ---- -uuu UFRML 2455 2550 4455 4550 xxxx xxxx xxxx xxxx uuuu uuuu SPPCON 2455 2550 4455 4550 ---- --00 ---- --00 ---- --uu SPPEPS 2455 2550 4455 4550 00-0 0000 00-0 0000 uu-u uuuu SPPCFG 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu SPPDATA 2455 2550 4455 4550 0000 0000 0000 0000 uuuu uuuu TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED) Register Applicable Devices Power-on Reset, Brown-out Reset MCLR Resets, WDT Reset, RESET Instruction, Stack Resets Wake-up via WDT or Interrupt Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition. Shaded cells indicate conditions do not apply for the designated device. Note 1: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack. 2: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up). 3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector (0008h or 0018h). 4: See Table 4-3 for Reset value for specific condition. 5: PORTA<6>, LATA<6> and TRISA<6> are enabled depending on the oscillator mode selected. When not enabled as PORTA pins, they are disabled and read ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 58 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 59 PIC18F2455/2550/4455/4550 5.0 MEMORY ORGANIZATION There are three types of memory in PIC18 enhanced microcontroller devices: • Program Memory • Data RAM • Data EEPROM As Harvard architecture devices, the data and program memories use separate busses; this allows for concurrent access of the two memory spaces. The data EEPROM, for practical purposes, can be regarded as a peripheral device, since it is addressed and accessed through a set of control registers. Additional detailed information on the operation of the Flash program memory is provided in Section 6.0 “Flash Program Memory”. Data EEPROM is discussed separately in Section 7.0 “Data EEPROM Memory”. 5.1 Program Memory Organization PIC18 microcontrollers implement a 21-bit program counter which is capable of addressing a 2-Mbyte program memory space. Accessing a location between the upper boundary of the physically implemented memory and the 2-Mbyte address will return all ‘0’s (a NOP instruction). The PIC18F2455 and PIC18F4455 each have 24 Kbytes of Flash memory and can store up to 12,288 single-word instructions. The PIC18F2550 and PIC18F4550 each have 32 Kbytes of Flash memory and can store up to 16,384 single-word instructions. PIC18 devices have two interrupt vectors. The Reset vector address is at 0000h and the interrupt vector addresses are at 0008h and 0018h. The program memory maps for PIC18FX455 and PIC18FX550 devices are shown in Figure 5-1. FIGURE 5-1: PROGRAM MEMORY MAP AND STACK PC<20:0> Stack Level 1 • Stack Level 31 Reset Vector Low-Priority Interrupt Vector •• CALL, RCALL, RETURN, RETFIE, RETLW, CALLW, 21 0000h 0018h On-Chip Program Memory High-Priority Interrupt Vector 0008h User Memory Space 1FFFFFh 6000h 5FFFh Read ‘0’ 200000h PC<20:0> Stack Level 1 • Stack Level 31 Reset Vector Low-Priority Interrupt Vector •• CALL, RCALL, RETURN, RETFIE, RETLW, CALLW, 21 0000h 0018h 8000h 7FFFh On-Chip Program Memory High-Priority Interrupt Vector 0008h User Memory Space Read ‘0’ 1FFFFFh 200000h 24 Kbyte Devices 32 Kbyte Device ADDULNK, SUBULNK ADDULNK, SUBULNK PIC18F2455/2550/4455/4550 DS39632E-page 60 © 2009 Microchip Technology Inc. 5.1.1 PROGRAM COUNTER The Program Counter (PC) specifies the address of the instruction to fetch for execution. The PC is 21 bits wide and is contained in three separate 8-bit registers. The low byte, known as the PCL register, is both readable and writable. The high byte, or PCH register, contains the PC<15:8> bits; it is not directly readable or writable. Updates to the PCH register are performed through the PCLATH register. The upper byte is called PCU. This register contains the PC<20:16> bits; it is also not directly readable or writable. Updates to the PCU register are performed through the PCLATU register. The contents of PCLATH and PCLATU are transferred to the program counter by any operation that writes PCL. Similarly, the upper two bytes of the program counter are transferred to PCLATH and PCLATU by an operation that reads PCL. This is useful for computed offsets to the PC (see Section 5.1.4.1 “Computed GOTO”). The PC addresses bytes in the program memory. To prevent the PC from becoming misaligned with word instructions, the Least Significant bit of PCL is fixed to a value of ‘0’. The PC increments by 2 to address sequential instructions in the program memory. The CALL, RCALL and GOTO program branch instructions write to the program counter directly. For these instructions, the contents of PCLATH and PCLATU are not transferred to the program counter. 5.1.2 RETURN ADDRESS STACK The return address stack allows any combination of up to 31 program calls and interrupts to occur. The PC is pushed onto the stack when a CALL or RCALL instruction is executed or an interrupt is Acknowledged. The PC value is pulled off the stack on a RETURN, RETLW or a RETFIE instruction. PCLATU and PCLATH are not affected by any of the RETURN or CALL instructions. The stack operates as a 31-word by 21-bit RAM and a 5-bit Stack Pointer, STKPTR. The stack space is not part of either program or data space. The Stack Pointer is readable and writable and the address on the top of the stack is readable and writable through the Top-of-Stack Special Function Registers. Data can also be pushed to, or popped from the stack, using these registers. A CALL type instruction causes a push onto the stack. The Stack Pointer is first incremented and the location pointed to by the Stack Pointer is written with the contents of the PC (already pointing to the instruction following the CALL). A RETURN type instruction causes a pop from the stack. The contents of the location pointed to by the STKPTR are transferred to the PC and then the Stack Pointer is decremented. The Stack Pointer is initialized to ‘00000’ after all Resets. There is no RAM associated with the location corresponding to a Stack Pointer value of ‘00000’; this is only a Reset value. Status bits indicate if the stack is full, has overflowed or has underflowed. 5.1.2.1 Top-of-Stack Access Only the top of the return address stack (TOS) is readable and writable. A set of three registers, TOSU:TOSH:TOSL, hold the contents of the stack location pointed to by the STKPTR register (Figure 5-2). This allows users to implement a software stack if necessary. After a CALL, RCALL or interrupt, the software can read the pushed value by reading the TOSU:TOSH:TOSL registers. These values can be placed on a user-defined software stack. At return time, the software can return these values to TOSU:TOSH:TOSL and do a return. The user must disable the global interrupt enable bits while accessing the stack to prevent inadvertent stack corruption. FIGURE 5-2: RETURN ADDRESS STACK AND ASSOCIATED REGISTERS 00011 001A34h 11111 11110 11101 00010 00001 00000 00010 Return Address Stack<20:0> Top-of-Stack 000D58h TOSU TOSH TOSL 00h 1Ah 34h STKPTR<4:0> Top-of-Stack Registers Stack Pointer © 2009 Microchip Technology Inc. DS39632E-page 61 PIC18F2455/2550/4455/4550 5.1.2.2 Return Stack Pointer (STKPTR) The STKPTR register (Register 5-1) contains the Stack Pointer value, the STKFUL (Stack Full) status bit and the STKUNF (Stack Underflow) status bit. The value of the Stack Pointer can be 0 through 31. The Stack Pointer increments before values are pushed onto the stack and decrements after values are popped off the stack. On Reset, the Stack Pointer value will be zero. The user may read and write the Stack Pointer value. This feature can be used by a Real-Time Operating System (RTOS) for return stack maintenance. After the PC is pushed onto the stack 31 times (without popping any values off the stack), the STKFUL bit is set. The STKFUL bit is cleared by software or by a POR. The action that takes place when the stack becomes full depends on the state of the STVREN (Stack Overflow Reset Enable) Configuration bit. (Refer to Section 25.1 “Configuration Bits” for a description of the device Configuration bits.) If STVREN is set (default), the 31st push will push the (PC + 2) value onto the stack, set the STKFUL bit and reset the device. The STKFUL bit will remain set and the Stack Pointer will be set to zero. If STVREN is cleared, the STKFUL bit will be set on the 31st push and the Stack Pointer will increment to 31. Any additional pushes will not overwrite the 31st push and the STKPTR will remain at 31. When the stack has been popped enough times to unload the stack, the next pop will return a value of zero to the PC and sets the STKUNF bit, while the Stack Pointer remains at zero. The STKUNF bit will remain set until cleared by software or until a POR occurs. 5.1.2.3 PUSH and POP Instructions Since the Top-of-Stack is readable and writable, the ability to push values onto the stack and pull values off the stack, without disturbing normal program execution, is a desirable feature. The PIC18 instruction set includes two instructions, PUSH and POP, that permit the TOS to be manipulated under software control. TOSU, TOSH and TOSL can be modified to place data or a return address on the stack. The PUSH instruction places the current PC value onto the stack. This increments the Stack Pointer and loads the current PC value onto the stack. The POP instruction discards the current TOS by decrementing the Stack Pointer. The previous value pushed onto the stack then becomes the TOS value. Note: Returning a value of zero to the PC on an underflow has the effect of vectoring the program to the Reset vector, where the stack conditions can be verified and appropriate actions can be taken. This is not the same as a Reset, as the contents of the SFRs are not affected. REGISTER 5-1: STKPTR: STACK POINTER REGISTER R/C-0 R/C-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 STKFUL(1) STKUNF(1) — SP4 SP3 SP2 SP1 SP0 bit 7 bit 0 Legend: C = Clearable bit R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 STKFUL: Stack Full Flag bit(1) 1 = Stack became full or overflowed 0 = Stack has not become full or overflowed bit 6 STKUNF: Stack Underflow Flag bit(1) 1 = Stack underflow occurred 0 = Stack underflow did not occur bit 5 Unimplemented: Read as ‘0’ bit 4-0 SP4:SP0: Stack Pointer Location bits Note 1: Bit 7 and bit 6 are cleared by user software or by a POR. PIC18F2455/2550/4455/4550 DS39632E-page 62 © 2009 Microchip Technology Inc. 5.1.2.4 Stack Full and Underflow Resets Device Resets on stack overflow and stack underflow conditions are enabled by setting the STVREN bit in Configuration Register 4L. When STVREN is set, a full or underflow condition will set the appropriate STKFUL or STKUNF bit and then cause a device Reset. When STVREN is cleared, a full or underflow condition will set the appropriate STKFUL or STKUNF bit but not cause a device Reset. The STKFUL or STKUNF bits are cleared by user software or a Power-on Reset. 5.1.3 FAST REGISTER STACK A Fast Register Stack is provided for the STATUS, WREG and BSR registers to provide a “fast return” option for interrupts. Each stack is only one level deep and is neither readable nor writable. It is loaded with the current value of the corresponding register when the processor vectors for an interrupt. All interrupt sources will push values into the stack registers. The values in the registers are then loaded back into their associated registers if the RETFIE, FAST instruction is used to return from the interrupt. If both low and high-priority interrupts are enabled, the stack registers cannot be used reliably to return from low-priority interrupts. If a high-priority interrupt occurs while servicing a low-priority interrupt, the stack register values stored by the low-priority interrupt will be overwritten. In these cases, users must save the key registers in software during a low-priority interrupt. If interrupt priority is not used, all interrupts may use the Fast Register Stack for returns from interrupt. If no interrupts are used, the Fast Register Stack can be used to restore the STATUS, WREG and BSR registers at the end of a subroutine call. To use the Fast Register Stack for a subroutine call, a CALL label, FAST instruction must be executed to save the STATUS, WREG and BSR registers to the Fast Register Stack. A RETURN, FAST instruction is then executed to restore these registers from the Fast Register Stack. Example 5-1 shows a source code example that uses the Fast Register Stack during a subroutine call and return. EXAMPLE 5-1: FAST REGISTER STACK CODE EXAMPLE 5.1.4 LOOK-UP TABLES IN PROGRAM MEMORY There may be programming situations that require the creation of data structures, or look-up tables, in program memory. For PIC18 devices, look-up tables can be implemented in two ways: • Computed GOTO • Table Reads 5.1.4.1 Computed GOTO A computed GOTO is accomplished by adding an offset to the program counter. An example is shown in Example 5-2. A look-up table can be formed with an ADDWF PCL instruction and a group of RETLW nn instructions. The W register is loaded with an offset into the table before executing a call to that table. The first instruction of the called routine is the ADDWF PCL instruction. The next instruction executed will be one of the RETLW nn instructions that returns the value ‘nn’ to the calling function. The offset value (in WREG) specifies the number of bytes that the program counter should advance and should be multiples of 2 (LSb = 0). In this method, only one data byte may be stored in each instruction location and room on the return address stack is required. EXAMPLE 5-2: COMPUTED GOTO USING AN OFFSET VALUE 5.1.4.2 Table Reads and Table Writes A better method of storing data in program memory allows two bytes of data to be stored in each instruction location. Look-up table data may be stored two bytes per program word by using table reads and writes. The Table Pointer (TBLPTR) register specifies the byte address and the Table Latch (TABLAT) register contains the data that is read from or written to program memory. Data is transferred to or from program memory one byte at a time. Table read and table write operations are discussed further in Section 6.1 “Table Reads and Table Writes”. CALL SUB1, FAST ;STATUS, WREG, BSR ;SAVED IN FAST REGISTER ;STACK • • SUB1 • • RETURN, FAST ;RESTORE VALUES SAVED ;IN FAST REGISTER STACK MOVF OFFSET, W CALL TABLE ORG nn00h TABLE ADDWF PCL RETLW nnh RETLW nnh RETLW nnh . . . © 2009 Microchip Technology Inc. DS39632E-page 63 PIC18F2455/2550/4455/4550 5.2 PIC18 Instruction Cycle 5.2.1 CLOCKING SCHEME The microcontroller clock input, whether from an internal or external source, is internally divided by four to generate four non-overlapping quadrature clocks (Q1, Q2, Q3 and Q4). Internally, the program counter is incremented on every Q1; the instruction is fetched from the program memory and latched into the Instruction Register (IR) during Q4. The instruction is decoded and executed during the following Q1 through Q4. The clocks and instruction execution flow are shown in Figure 5-3. 5.2.2 INSTRUCTION FLOW/PIPELINING An “Instruction Cycle” consists of four Q cycles: Q1 through Q4. The instruction fetch and execute are pipelined in such a manner that a fetch takes one instruction cycle, while the decode and execute takes another instruction cycle. However, due to the pipelining, each instruction effectively executes in one cycle. If an instruction causes the program counter to change (e.g., GOTO), then two cycles are required to complete the instruction (Example 5-3). A fetch cycle begins with the Program Counter (PC) incrementing in Q1. In the execution cycle, the fetched instruction is latched into the Instruction Register (IR) in cycle Q1. This instruction is then decoded and executed during the Q2, Q3 and Q4 cycles. Data memory is read during Q2 (operand read) and written during Q4 (destination write). FIGURE 5-3: CLOCK/INSTRUCTION CYCLE EXAMPLE 5-3: INSTRUCTION PIPELINE FLOW Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 OSC1 Q1 Q2 Q3 Q4 PC OSC2/CLKO (RC mode) PC PC + 2 PC + 4 Fetch INST (PC) Execute INST (PC – 2) Fetch INST (PC + 2) Execute INST (PC) Fetch INST (PC + 4) Execute INST (PC + 2) Internal Phase Clock Note: All instructions are single cycle, except for any program branches. These take two cycles since the fetch instruction is “flushed” from the pipeline while the new instruction is being fetched and then executed. TCY0 TCY1 TCY2 TCY3 TCY4 TCY5 1. MOVLW 55h Fetch 1 Execute 1 2. MOVWF PORTB Fetch 2 Execute 2 3. BRA SUB_1 Fetch 3 Execute 3 4. BSF PORTA, BIT3 (Forced NOP) Fetch 4 Flush (NOP) 5. Instruction @ address SUB_1 Fetch SUB_1 Execute SUB_1 PIC18F2455/2550/4455/4550 DS39632E-page 64 © 2009 Microchip Technology Inc. 5.2.3 INSTRUCTIONS IN PROGRAM MEMORY The program memory is addressed in bytes. Instructions are stored as two bytes or four bytes in program memory. The Least Significant Byte of an instruction word is always stored in a program memory location with an even address (LSb = 0). To maintain alignment with instruction boundaries, the PC increments in steps of 2 and the LSb will always read ‘0’ (see Section 5.1.1 “Program Counter”). Figure 5-4 shows an example of how instruction words are stored in the program memory. The CALL and GOTO instructions have the absolute program memory address embedded into the instruction. Since instructions are always stored on word boundaries, the data contained in the instruction is a word address. The word address is written to PC<20:1>, which accesses the desired byte address in program memory. Instruction #2 in Figure 5-4 shows how the instruction, GOTO 0006h, is encoded in the program memory. Program branch instructions, which encode a relative address offset, operate in the same manner. The offset value stored in a branch instruction represents the number of single-word instructions that the PC will be offset by. Section 26.0 “Instruction Set Summary” provides further details of the instruction set. FIGURE 5-4: INSTRUCTIONS IN PROGRAM MEMORY 5.2.4 TWO-WORD INSTRUCTIONS The standard PIC18 instruction set has four two-word instructions: CALL, MOVFF, GOTO and LSFR. In all cases, the second word of the instructions always has ‘1111’ as its four Most Significant bits; the other 12 bits are literal data, usually a data memory address. The use of ‘1111’ in the 4 MSbs of an instruction specifies a special form of NOP. If the instruction is executed in proper sequence, immediately after the first word, the data in the second word is accessed and used by the instruction sequence. If the first word is skipped for some reason and the second word is executed by itself, a NOP is executed instead. This is necessary for cases when the two-word instruction is preceded by a conditional instruction that changes the PC. Example 5-4 shows how this works. EXAMPLE 5-4: TWO-WORD INSTRUCTIONS Word Address LSB = 1 LSB = 0 ↓ Program Memory Byte Locations → 000000h 000002h 000004h 000006h Instruction 1: MOVLW 055h 0Fh 55h 000008h Instruction 2: GOTO 0006h EFh 03h 00000Ah F0h 00h 00000Ch Instruction 3: MOVFF 123h, 456h C1h 23h 00000Eh F4h 56h 000010h 000012h 000014h Note: See Section 5.5 “Program Memory and the Extended Instruction Set” for information on two-word instruction in the extended instruction set. CASE 1: Object Code Source Code 0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0? 1100 0001 0010 0011 MOVFF REG1, REG2 ; No, skip this word 1111 0100 0101 0110 ; Execute this word as a NOP 0010 0100 0000 0000 ADDWF REG3 ; continue code CASE 2: Object Code Source Code 0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0? 1100 0001 0010 0011 MOVFF REG1, REG2 ; Yes, execute this word 1111 0100 0101 0110 ; 2nd word of instruction 0010 0100 0000 0000 ADDWF REG3 ; continue code © 2009 Microchip Technology Inc. DS39632E-page 65 PIC18F2455/2550/4455/4550 5.3 Data Memory Organization The data memory in PIC18 devices is implemented as static RAM. Each register in the data memory has a 12-bit address, allowing up to 4096 bytes of data memory. The memory space is divided into as many as 16 banks that contain 256 bytes each. PIC18F2455/2550/4455/4550 devices implement eight complete banks, for a total of 2048 bytes. Figure 5-5 shows the data memory organization for the devices. The data memory contains Special Function Registers (SFRs) and General Purpose Registers (GPRs). The SFRs are used for control and status of the controller and peripheral functions, while GPRs are used for data storage and scratchpad operations in the user’s application. Any read of an unimplemented location will read as ‘0’s. The instruction set and architecture allow operations across all banks. The entire data memory may be accessed by Direct, Indirect or Indexed Addressing modes. Addressing modes are discussed later in this subsection. To ensure that commonly used registers (SFRs and select GPRs) can be accessed in a single cycle, PIC18 devices implement an Access Bank. This is a 256-byte memory space that provides fast access to SFRs and the lower portion of GPR Bank 0 without using the BSR. Section 5.3.3 “Access Bank” provides a detailed description of the Access RAM. 5.3.1 USB RAM Banks 4 through 7 of the data memory are actually mapped to special dual port RAM. When the USB module is disabled, the GPRs in these banks are used like any other GPR in the data memory space. When the USB module is enabled, the memory in these banks is allocated as buffer RAM for USB operation. This area is shared between the microcontroller core and the USB Serial Interface Engine (SIE) and is used to transfer data directly between the two. It is theoretically possible to use the areas of USB RAM that are not allocated as USB buffers for normal scratchpad memory or other variable storage. In practice, the dynamic nature of buffer allocation makes this risky at best. Additionally, Bank 4 is used for USB buffer management when the module is enabled and should not be used for any other purposes during that time. Additional information on USB RAM and buffer operation is provided in Section 17.0 “Universal Serial Bus (USB)”. 5.3.2 BANK SELECT REGISTER (BSR) Large areas of data memory require an efficient addressing scheme to make rapid access to any address possible. Ideally, this means that an entire address does not need to be provided for each read or write operation. For PIC18 devices, this is accomplished with a RAM banking scheme. This divides the memory space into 16 contiguous banks of 256 bytes. Depending on the instruction, each location can be addressed directly by its full 12-bit address, or an 8-bit low-order address and a 4-bit Bank Pointer. Most instructions in the PIC18 instruction set make use of the Bank Pointer, known as the Bank Select Register (BSR). This SFR holds the 4 Most Significant bits of a location’s address; the instruction itself includes the eight Least Significant bits. Only the four lower bits of the BSR are implemented (BSR3:BSR0). The upper four bits are unused; they will always read ‘0’ and cannot be written to. The BSR can be loaded directly by using the MOVLB instruction. The value of the BSR indicates the bank in data memory. The eight bits in the instruction show the location in the bank and can be thought of as an offset from the bank’s lower boundary. The relationship between the BSR’s value and the bank division in data memory is shown in Figure 5-6. Since up to sixteen registers may share the same low-order address, the user must always be careful to ensure that the proper bank is selected before performing a data read or write. For example, writing what should be program data to an 8-bit address of F9h, while the BSR is 0Fh, will end up resetting the program counter. While any bank can be selected, only those banks that are actually implemented can be read or written to. Writes to unimplemented banks are ignored, while reads from unimplemented banks will return ‘0’s. Even so, the STATUS register will still be affected as if the operation was successful. The data memory map in Figure 5-5 indicates which banks are implemented. In the core PIC18 instruction set, only the MOVFF instruction fully specifies the 12-bit address of the source and target registers. This instruction ignores the BSR completely when it executes. All other instructions include only the low-order address as an operand and must use either the BSR or the Access Bank to locate their target registers. Note: The operation of some aspects of data memory are changed when the PIC18 extended instruction set is enabled. See Section 5.6 “Data Memory and the Extended Instruction Set” for more information. PIC18F2455/2550/4455/4550 DS39632E-page 66 © 2009 Microchip Technology Inc. FIGURE 5-5: DATA MEMORY MAP Bank 0 Bank 1 Bank 14 Bank 15 BSR<3:0> Data Memory Map = 0000 = 0001 = 1111 060h 05Fh F60h FFFh 00h 5Fh 60h FFh Access Bank When a = 0: The BSR is ignored and the Access Bank is used. The first 96 bytes are general purpose RAM (from Bank 0). The remaining 160 bytes are Special Function Registers (from Bank 15). When a = 1: The BSR specifies the bank used by the instruction. F5Fh F00h EFFh 1FFh 100h 0FFh Access RAM 000h FFh 00h FFh 00h FFh 00h GPR GPR SFR Access RAM High Access RAM Low Bank 2 = 0110 = 0010 (SFRs) 2FFh 200h 3FFh 300h 4FFh 400h 5FFh 500h 6FFh 600h 7FFh 700h 800h Bank 3 Bank 4 Bank 5 Bank 6 Bank 7 Bank 8 FFh 00h FFh 00h FFh 00h FFh 00h FFh 00h FFh 00h 00h GPR GPR(1) GPR GPR(1) GPR(1) GPR(1) FFh = 0011 = 0100 = 0101 = 0111 = 1000 Unused to Read as 00h = 1110 Note 1: These banks also serve as RAM buffer for USB operation. See Section 5.3.1 “USB RAM” for more information. Unused © 2009 Microchip Technology Inc. DS39632E-page 67 PIC18F2455/2550/4455/4550 FIGURE 5-6: USE OF THE BANK SELECT REGISTER (DIRECT ADDRESSING) 5.3.3 ACCESS BANK While the use of the BSR, with an embedded 8-bit address, allows users to address the entire range of data memory, it also means that the user must always ensure that the correct bank is selected. Otherwise, data may be read from or written to the wrong location. This can be disastrous if a GPR is the intended target of an operation but an SFR is written to instead. Verifying and/or changing the BSR for each read or write to data memory can become very inefficient. To streamline access for the most commonly used data memory locations, the data memory is configured with an Access Bank, which allows users to access a mapped block of memory without specifying a BSR. The Access Bank consists of the first 96 bytes of memory (00h-5Fh) in Bank 0 and the last 160 bytes of memory (60h-FFh) in Block 15. The lower half is known as the “Access RAM” and is composed of GPRs. The upper half is where the device’s SFRs are mapped. These two areas are mapped contiguously in the Access Bank and can be addressed in a linear fashion by an 8-bit address (Figure 5-5). The Access Bank is used by core PIC18 instructions that include the Access RAM bit (the ‘a’ parameter in the instruction). When ‘a’ is equal to ‘1’, the instruction uses the BSR and the 8-bit address included in the opcode for the data memory address. When ‘a’ is ‘0’, however, the instruction is forced to use the Access Bank address map; the current value of the BSR is ignored entirely. Using this “forced” addressing allows the instruction to operate on a data address in a single cycle without updating the BSR first. For 8-bit addresses of 60h and above, this means that users can evaluate and operate on SFRs more efficiently. The Access RAM below 60h is a good place for data values that the user might need to access rapidly, such as immediate computational results or common program variables. Access RAM also allows for faster and more code efficient context saving and switching of variables. The mapping of the Access Bank is slightly different when the extended instruction set is enabled (XINST Configuration bit = 1). This is discussed in more detail in Section 5.6.3 “Mapping the Access Bank in Indexed Literal Offset Mode”. 5.3.4 GENERAL PURPOSE REGISTER FILE PIC18 devices may have banked memory in the GPR area. This is data RAM which is available for use by all instructions. GPRs start at the bottom of Bank 0 (address 000h) and grow upwards towards the bottom of the SFR area. GPRs are not initialized by a Power-on Reset and are unchanged on all other Resets. Note 1: The Access RAM bit of the instruction can be used to force an override of the selected bank (BSR<3:0>) to the registers of the Access Bank. 2: The MOVFF instruction embeds the entire 12-bit address in the instruction. Data Memory Bank Select(2) 7 0 From Opcode(2) 0 0 0 0 000h 100h 200h 300h F00h E00h FFFh Bank 0 Bank 1 Bank 2 Bank 14 Bank 15 00h FFh 00h FFh 00h FFh 00h FFh 00h FFh 00h FFh Bank 3 through Bank 13 0 0 1 1 1 1 1 1 1 1 1 1 7 0 BSR(1) PIC18F2455/2550/4455/4550 DS39632E-page 68 © 2009 Microchip Technology Inc. 5.3.5 SPECIAL FUNCTION REGISTERS The Special Function Registers (SFRs) are registers used by the CPU and peripheral modules for controlling the desired operation of the device. These registers are implemented as static RAM in the data memory space. SFRs start at the top of data memory and extend downward to occupy the top segment of Bank 15, from F60h to FFFh. A list of these registers is given in Table 5-1 and Table 5-2. The SFRs can be classified into two sets: those associated with the “core” device functionality (ALU, Resets and interrupts) and those related to the peripheral functions. The Reset and interrupt registers are described in their respective chapters, while the ALU’s STATUS register is described later in this section. Registers related to the operation of a peripheral feature are described in the chapter for that peripheral. The SFRs are typically distributed among the peripherals whose functions they control. Unused SFR locations are unimplemented and read as ‘0’s. TABLE 5-1: SPECIAL FUNCTION REGISTER MAP Address Name Address Name Address Name Address Name Address Name FFFh TOSU FDFh INDF2(1) FBFh CCPR1H F9Fh IPR1 F7Fh UEP15 FFEh TOSH FDEh POSTINC2(1) FBEh CCPR1L F9Eh PIR1 F7Eh UEP14 FFDh TOSL FDDh POSTDEC2(1) FBDh CCP1CON F9Dh PIE1 F7Dh UEP13 FFCh STKPTR FDCh PREINC2(1) FBCh CCPR2H F9Ch —(2) F7Ch UEP12 FFBh PCLATU FDBh PLUSW2(1) FBBh CCPR2L F9Bh OSCTUNE F7Bh UEP11 FFAh PCLATH FDAh FSR2H FBAh CCP2CON F9Ah —(2) F7Ah UEP10 FF9h PCL FD9h FSR2L FB9h —(2) F99h —(2) F79h UEP9 FF8h TBLPTRU FD8h STATUS FB8h BAUDCON F98h —(2) F78h UEP8 FF7h TBLPTRH FD7h TMR0H FB7h ECCP1DEL F97h —(2) F77h UEP7 FF6h TBLPTRL FD6h TMR0L FB6h ECCP1AS F96h TRISE(3) F76h UEP6 FF5h TABLAT FD5h T0CON FB5h CVRCON F95h TRISD(3) F75h UEP5 FF4h PRODH FD4h —(2) FB4h CMCON F94h TRISC F74h UEP4 FF3h PRODL FD3h OSCCON FB3h TMR3H F93h TRISB F73h UEP3 FF2h INTCON FD2h HLVDCON FB2h TMR3L F92h TRISA F72h UEP2 FF1h INTCON2 FD1h WDTCON FB1h T3CON F91h —(2) F71h UEP1 FF0h INTCON3 FD0h RCON FB0h SPBRGH F90h —(2) F70h UEP0 FEFh INDF0(1) FCFh TMR1H FAFh SPBRG F8Fh —(2) F6Fh UCFG FEEh POSTINC0(1) FCEh TMR1L FAEh RCREG F8Eh —(2) F6Eh UADDR FEDh POSTDEC0(1) FCDh T1CON FADh TXREG F8Dh LATE(3) F6Dh UCON FECh PREINC0(1) FCCh TMR2 FACh TXSTA F8Ch LATD(3) F6Ch USTAT FEBh PLUSW0(1) FCBh PR2 FABh RCSTA F8Bh LATC F6Bh UEIE FEAh FSR0H FCAh T2CON FAAh —(2) F8Ah LATB F6Ah UEIR FE9h FSR0L FC9h SSPBUF FA9h EEADR F89h LATA F69h UIE FE8h WREG FC8h SSPADD FA8h EEDATA F88h —(2) F68h UIR FE7h INDF1(1) FC7h SSPSTAT FA7h EECON2(1) F87h —(2) F67h UFRMH FE6h POSTINC1(1) FC6h SSPCON1 FA6h EECON1 F86h —(2) F66h UFRML FE5h POSTDEC1(1) FC5h SSPCON2 FA5h —(2) F85h —(2) F65h SPPCON(3) FE4h PREINC1(1) FC4h ADRESH FA4h —(2) F84h PORTE F64h SPPEPS(3) FE3h PLUSW1(1) FC3h ADRESL FA3h —(2) F83h PORTD(3) F63h SPPCFG(3) FE2h FSR1H FC2h ADCON0 FA2h IPR2 F82h PORTC F62h SPPDATA(3) FE1h FSR1L FC1h ADCON1 FA1h PIR2 F81h PORTB F61h —(2) FE0h BSR FC0h ADCON2 FA0h PIE2 F80h PORTA F60h —(2) Note 1: Not a physical register. 2: Unimplemented registers are read as ‘0’. 3: These registers are implemented only on 40/44-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 69 PIC18F2455/2550/4455/4550 TABLE 5-2: REGISTER FILE SUMMARY File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on POR, BOR Details on page TOSU — — — Top-of-Stack Upper Byte (TOS<20:16>) ---0 0000 53, 60 TOSH Top-of-Stack High Byte (TOS<15:8>) 0000 0000 53, 60 TOSL Top-of-Stack Low Byte (TOS<7:0>) 0000 0000 53, 60 STKPTR STKFUL STKUNF — SP4 SP3 SP2 SP1 SP0 00-0 0000 53, 61 PCLATU — — — Holding Register for PC<20:16> ---0 0000 53, 60 PCLATH Holding Register for PC<15:8> 0000 0000 53, 60 PCL PC Low Byte (PC<7:0>) 0000 0000 53, 60 TBLPTRU — — bit 21(1) Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) --00 0000 53, 84 TBLPTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 0000 0000 53, 84 TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 0000 0000 53, 84 TABLAT Program Memory Table Latch 0000 0000 53, 84 PRODH Product Register High Byte xxxx xxxx 53, 97 PRODL Product Register Low Byte xxxx xxxx 53, 97 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 53, 101 INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP 1111 -1-1 53, 102 INTCON3 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF 11-0 0-00 53, 103 INDF0 Uses contents of FSR0 to address data memory – value of FSR0 not changed (not a physical register) N/A 53, 75 POSTINC0 Uses contents of FSR0 to address data memory – value of FSR0 post-incremented (not a physical register) N/A 53, 76 POSTDEC0 Uses contents of FSR0 to address data memory – value of FSR0 post-decremented (not a physical register) N/A 53, 76 PREINC0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) N/A 53, 76 PLUSW0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) – value of FSR0 offset by W N/A 53, 76 FSR0H — — — — Indirect Data Memory Address Pointer 0 High Byte ---- 0000 53, 75 FSR0L Indirect Data Memory Address Pointer 0 Low Byte xxxx xxxx 53, 75 WREG Working Register xxxx xxxx 53 INDF1 Uses contents of FSR1 to address data memory – value of FSR1 not changed (not a physical register) N/A 53, 75 POSTINC1 Uses contents of FSR1 to address data memory – value of FSR1 post-incremented (not a physical register) N/A 53, 76 POSTDEC1 Uses contents of FSR1 to address data memory – value of FSR1 post-decremented (not a physical register) N/A 53, 76 PREINC1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) N/A 53, 76 PLUSW1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) – value of FSR1 offset by W N/A 53, 76 FSR1H — — — — Indirect Data Memory Address Pointer 1 High Byte ---- 0000 53, 75 FSR1L Indirect Data Memory Address Pointer 1 Low Byte xxxx xxxx 53, 75 BSR — — — — Bank Select Register ---- 0000 54, 65 INDF2 Uses contents of FSR2 to address data memory – value of FSR2 not changed (not a physical register) N/A 54, 75 POSTINC2 Uses contents of FSR2 to address data memory – value of FSR2 post-incremented (not a physical register) N/A 54, 76 POSTDEC2 Uses contents of FSR2 to address data memory – value of FSR2 post-decremented (not a physical register) N/A 54, 76 PREINC2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) N/A 54, 76 PLUSW2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) – value of FSR2 offset by W N/A 54, 76 FSR2H — — — — Indirect Data Memory Address Pointer 2 High Byte ---- 0000 54, 75 FSR2L Indirect Data Memory Address Pointer 2 Low Byte xxxx xxxx 54, 75 STATUS — — — N OV Z DC C ---x xxxx 54, 73 TMR0H Timer0 Register High Byte 0000 0000 54, 129 TMR0L Timer0 Register Low Byte xxxx xxxx 54, 129 T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 1111 1111 54, 127 Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition. Shaded cells are unimplemented, read as ‘0’. Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits. 2: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 3: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices; individual unimplemented bits should be interpreted as ‘-’. 4: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. 5: RE3 is only available as a port pin when the MCLRE Configuration bit is clear; otherwise, the bit reads as ‘0’. 6: RC5 and RC4 are only available as port pins when the USB module is disabled (UCON<3> = 0). 7: I2C™ Slave mode only. PIC18F2455/2550/4455/4550 DS39632E-page 70 © 2009 Microchip Technology Inc. OSCCON IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 0100 q000 54, 33 HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 0-00 0101 54, 285 WDTCON — — — — — — — SWDTEN --- ---0 54, 304 RCON IPEN SBOREN(2) — RI TO PD POR BOR 0q-1 11q0 54, 46 TMR1H Timer1 Register High Byte xxxx xxxx 54, 136 TMR1L Timer1 Register Low Byte xxxx xxxx 54, 136 T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 0000 0000 54, 131 TMR2 Timer2 Register 0000 0000 54, 138 PR2 Timer2 Period Register 1111 1111 54, 138 T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 54, 137 SSPBUF MSSP Receive Buffer/Transmit Register xxxx xxxx 54, 198, 207 SSPADD MSSP Address Register in I2C™ Slave mode. MSSP Baud Rate Reload Register in I2C™ Master mode. 0000 0000 54, 207 SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 54, 198, 208 SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 54, 199, 209 SSPCON2 GCEN ACKSTAT ACKDT/ ADMSK5(7) ACKEN/ ADMSK4(7) RCEN/ ADMSK3(7) PEN/ ADMSK2(7) RSEN/ ADMSK1(7) SEN 0000 0000 54, 210 ADRESH A/D Result Register High Byte xxxx xxxx 54, 274 ADRESL A/D Result Register Low Byte xxxx xxxx 54, 274 ADCON0 — — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON --00 0000 54, 265 ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 --00 0qqq 54, 266 ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 0-00 0000 54, 267 CCPR1H Capture/Compare/PWM Register 1 High Byte xxxx xxxx 55, 144 CCPR1L Capture/Compare/PWM Register 1 Low Byte xxxx xxxx 55, 144 CCP1CON P1M1(3) P1M0(3) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 0000 0000 55, 143, 151 CCPR2H Capture/Compare/PWM Register 2 High Byte xxxx xxxx 55, 144 CCPR2L Capture/Compare/PWM Register 2 Low Byte xxxx xxxx 55, 144 CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 55, 143 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 0100 0-00 55, 246 ECCP1DEL PRSEN PDC6(3) PDC5(3) PDC4(3) PDC3(3) PDC2(3) PDC1(3) PDC0(3) 0000 0000 55, 160 ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(3) PSSBD0(3) 0000 0000 55, 161 CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 0000 0000 55, 281 CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 0000 0111 55, 275 TMR3H Timer3 Register High Byte xxxx xxxx 55, 141 TMR3L Timer3 Register Low Byte xxxx xxxx 55, 141 T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 0000 0000 55, 139 SPBRGH EUSART Baud Rate Generator Register High Byte 0000 0000 55, 247 SPBRG EUSART Baud Rate Generator Register Low Byte 0000 0000 55, 247 RCREG EUSART Receive Register 0000 0000 55, 256 TXREG EUSART Transmit Register 0000 0000 55, 253 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 0000 0010 55, 244 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 55, 245 TABLE 5-2: REGISTER FILE SUMMARY (CONTINUED) File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on POR, BOR Details on page Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition. Shaded cells are unimplemented, read as ‘0’. Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits. 2: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 3: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices; individual unimplemented bits should be interpreted as ‘-’. 4: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. 5: RE3 is only available as a port pin when the MCLRE Configuration bit is clear; otherwise, the bit reads as ‘0’. 6: RC5 and RC4 are only available as port pins when the USB module is disabled (UCON<3> = 0). 7: I2C™ Slave mode only. © 2009 Microchip Technology Inc. DS39632E-page 71 PIC18F2455/2550/4455/4550 EEADR EEPROM Address Register 0000 0000 55, 91 EEDATA EEPROM Data Register 0000 0000 55, 91 EECON2 EEPROM Control Register 2 (not a physical register) 0000 0000 55, 82 EECON1 EEPGD CFGS — FREE WRERR WREN WR RD xx-0 x000 55, 83 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 1111 1111 56, 109 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 0000 0000 56, 105 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 0000 0000 56, 107 IPR1 SPPIP(3) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 56, 108 PIR1 SPPIF(3) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 56, 104 PIE1 SPPIE(3) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 56, 106 OSCTUNE INTSRC — — TUN4 TUN3 TUN2 TUN1 TUN0 0--0 0000 56, 28 TRISE(3) — — — — — TRISE2 TRISE1 TRISE0 ---- -111 56, 126 TRISD(3) TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 1111 1111 56, 124 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 11-- -111 56, 121 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 1111 1111 56, 118 TRISA — TRISA6(4) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 -111 1111 56, 115 LATE(3) — — — — — LATE2 LATE1 LATE0 ---- -xxx 56, 126 LATD(3) LATD7 LATD6 LATD5 LATD4 LATD3 LATD2 LATD1 LATD0 xxxx xxxx 56, 124 LATC LATC7 LATC6 — — — LATC2 LATC1 LATC0 xx-- -xxx 56, 121 LATB LATB7 LATB6 LATB5 LATB4 LATB3 LATB2 LATB1 LATB0 xxxx xxxx 56, 118 LATA — LATA6(4) LATA5 LATA4 LATA3 LATA2 LATA1 LATA0 -xxx xxxx 56, 115 PORTE RDPU(3) — — — RE3(5) RE2(3) RE1(3) RE0(3) 0--- x000 56, 125 PORTD(3) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 xxxx xxxx 56, 124 PORTC RC7 RC6 RC5(6) RC4(6) — RC2 RC1 RC0 xxxx -xxx 56, 121 PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxxx xxxx 56, 118 PORTA — RA6(4) RA5 RA4 RA3 RA2 RA1 RA0 -x0x 0000 56, 115 UEP15 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP14 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP13 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP12 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP11 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP10 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP9 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP8 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP7 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP6 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP5 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP4 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP3 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP2 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP1 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 UEP0 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL ---0 0000 57, 172 TABLE 5-2: REGISTER FILE SUMMARY (CONTINUED) File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on POR, BOR Details on page Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition. Shaded cells are unimplemented, read as ‘0’. Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits. 2: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 3: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices; individual unimplemented bits should be interpreted as ‘-’. 4: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. 5: RE3 is only available as a port pin when the MCLRE Configuration bit is clear; otherwise, the bit reads as ‘0’. 6: RC5 and RC4 are only available as port pins when the USB module is disabled (UCON<3> = 0). 7: I2C™ Slave mode only. PIC18F2455/2550/4455/4550 DS39632E-page 72 © 2009 Microchip Technology Inc. UCFG UTEYE UOEMON — UPUEN UTRDIS FSEN PPB1 PPB0 00-0 0000 57, 168 UADDR — ADDR6 ADDR5 ADDR4 ADDR3 ADDR2 ADDR1 ADDR0 -000 0000 57, 173 UCON — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — -0x0 000- 57, 166 USTAT — ENDP3 ENDP2 ENDP1 ENDP0 DIR PPBI — -xxx xxx- 57, 171 UEIE BTSEE — — BTOEE DFN8EE CRC16EE CRC5EE PIDEE 0--0 0000 57, 185 UEIR BTSEF — — BTOEF DFN8EF CRC16EF CRC5EF PIDEF 0--0 0000 57, 184 UIE — SOFIE STALLIE IDLEIE TRNIE ACTVIE UERRIE URSTIE -000 0000 57, 183 UIR — SOFIF STALLIF IDLEIF TRNIF ACTVIF UERRIF URSTIF -000 0000 57, 181 UFRMH — — — — — FRM10 FRM9 FRM8 ---- -xxx 57, 173 UFRML FRM7 FRM6 FRM5 FRM4 FRM3 FRM2 FRM1 FRM0 xxxx xxxx 57, 173 SPPCON(3) — — — — — — SPPOWN SPPEN ---- --00 57, 191 SPPEPS(3) RDSPP WRSPP — SPPBUSY ADDR3 ADDR2 ADDR1 ADDR0 00-0 0000 57, 195 SPPCFG(3) CLKCFG1 CLKCFG0 CSEN CLK1EN WS3 WS2 WS1 WS0 0000 0000 57, 192 SPPDATA(3) DATA7 DATA6 DATA5 DATA4 DATA3 DATA2 DATA1 DATA0 0000 0000 57, 196 TABLE 5-2: REGISTER FILE SUMMARY (CONTINUED) File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on POR, BOR Details on page Legend: x = unknown, u = unchanged, - = unimplemented, q = value depends on condition. Shaded cells are unimplemented, read as ‘0’. Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits. 2: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 3: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices; individual unimplemented bits should be interpreted as ‘-’. 4: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. 5: RE3 is only available as a port pin when the MCLRE Configuration bit is clear; otherwise, the bit reads as ‘0’. 6: RC5 and RC4 are only available as port pins when the USB module is disabled (UCON<3> = 0). 7: I2C™ Slave mode only. © 2009 Microchip Technology Inc. DS39632E-page 73 PIC18F2455/2550/4455/4550 5.3.6 STATUS REGISTER The STATUS register, shown in Register 5-2, contains the arithmetic status of the ALU. As with any other SFR, it can be the operand for any instruction. If the STATUS register is the destination for an instruction that affects the Z, DC, C, OV or N bits, the results of the instruction are not written; instead, the STATUS register is updated according to the instruction performed. Therefore, the result of an instruction with the STATUS register as its destination may be different than intended. As an example, CLRF STATUS will set the Z bit and leave the remaining Status bits unchanged (‘000u u1uu’). It is recommended that only BCF, BSF, SWAPF, MOVFF and MOVWF instructions are used to alter the STATUS register because these instructions do not affect the Z, C, DC, OV or N bits in the STATUS register. For other instructions that do not affect Status bits, see the instruction set summaries in Table 26-2 and Table 26-3. Note: The C and DC bits operate as the Borrow and Digit Borrow bits, respectively, in subtraction. REGISTER 5-2: STATUS REGISTER U-0 U-0 U-0 R/W-x R/W-x R/W-x R/W-x R/W-x — — — N OV Z DC(1) C(2) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-5 Unimplemented: Read as ‘0’ bit 4 N: Negative bit This bit is used for signed arithmetic (2’s complement). It indicates whether the result was negative (ALU MSB = 1). 1 = Result was negative 0 = Result was positive bit 3 OV: Overflow bit This bit is used for signed arithmetic (2’s complement). It indicates an overflow of the 7-bit magnitude which causes the sign bit (bit 7 of the result) to change state. 1 = Overflow occurred for signed arithmetic (in this arithmetic operation) 0 = No overflow occurred bit 2 Z: Zero bit 1 = The result of an arithmetic or logic operation is zero 0 = The result of an arithmetic or logic operation is not zero bit 1 DC: Digit Carry/Borrow bit(1) For ADDWF, ADDLW, SUBLW and SUBWF instructions: 1 = A carry-out from the 4th low-order bit of the result occurred 0 = No carry-out from the 4th low-order bit of the result bit 0 C: Carry/Borrow bit(2) For ADDWF, ADDLW, SUBLW and SUBWF instructions: 1 = A carry-out from the Most Significant bit of the result occurred 0 = No carry-out from the Most Significant bit of the result occurred Note 1: For Borrow, the polarity is reversed. A subtraction is executed by adding the 2’s complement of the second operand. For rotate (RRF, RLF) instructions, this bit is loaded with either bit 4 or bit 3 of the source register. 2: For Borrow, the polarity is reversed. A subtraction is executed by adding the 2’s complement of the second operand. For rotate (RRF, RLF) instructions, this bit is loaded with either the high or low-order bit of the source register. PIC18F2455/2550/4455/4550 DS39632E-page 74 © 2009 Microchip Technology Inc. 5.4 Data Addressing Modes While the program memory can be addressed in only one way – through the program counter – information in the data memory space can be addressed in several ways. For most instructions, the addressing mode is fixed. Other instructions may use up to three modes, depending on which operands are used and whether or not the extended instruction set is enabled. The addressing modes are: • Inherent • Literal • Direct • Indirect An additional addressing mode, Indexed Literal Offset, is available when the extended instruction set is enabled (XINST Configuration bit = 1). Its operation is discussed in greater detail in Section 5.6.1 “Indexed Addressing with Literal Offset”. 5.4.1 INHERENT AND LITERAL ADDRESSING Many PIC18 control instructions do not need any argument at all; they either perform an operation that globally affects the device or they operate implicitly on one register. This addressing mode is known as Inherent Addressing. Examples include SLEEP, RESET and DAW. Other instructions work in a similar way but require an additional explicit argument in the opcode. This is known as Literal Addressing mode because they require some literal value as an argument. Examples include ADDLW and MOVLW, which respectively, add or move a literal value to the W register. Other examples include CALL and GOTO, which include a 20-bit program memory address. 5.4.2 DIRECT ADDRESSING Direct Addressing mode specifies all or part of the source and/or destination address of the operation within the opcode itself. The options are specified by the arguments accompanying the instruction. In the core PIC18 instruction set, bit-oriented and byte-oriented instructions use some version of Direct Addressing by default. All of these instructions include some 8-bit literal address as their Least Significant Byte. This address specifies either a register address in one of the banks of data RAM (Section 5.3.4 “General Purpose Register File”) or a location in the Access Bank (Section 5.3.3 “Access Bank”) as the data source for the instruction. The Access RAM bit ‘a’ determines how the address is interpreted. When ‘a’ is ‘1’, the contents of the BSR (Section 5.3.2 “Bank Select Register (BSR)”) are used with the address to determine the complete 12-bit address of the register. When ‘a’ is ‘0’, the address is interpreted as being a register in the Access Bank. Addressing that uses the Access RAM is sometimes also known as Direct Forced Addressing mode. A few instructions, such as MOVFF, include the entire 12-bit address (either source or destination) in their opcodes. In these cases, the BSR is ignored entirely. The destination of the operation’s results is determined by the destination bit ‘d’. When ‘d’ is ‘1’, the results are stored back in the source register, overwriting its original contents. When ‘d’ is ‘0’, the results are stored in the W register. Instructions without the ‘d’ argument have a destination that is implicit in the instruction; their destination is either the target register being operated on or the W register. 5.4.3 INDIRECT ADDRESSING Indirect Addressing allows the user to access a location in data memory without giving a fixed address in the instruction. This is done by using File Select Registers (FSRs) as pointers to the locations to be read or written to. Since the FSRs are themselves located in RAM as Special Function Registers, they can also be directly manipulated under program control. This makes FSRs very useful in implementing data structures, such as tables and arrays in data memory. The registers for Indirect Addressing are also implemented with Indirect File Operands (INDFs) that permit automatic manipulation of the pointer value with auto-incrementing, auto-decrementing or offsetting with another value. This allows for efficient code, using loops, such as the example of clearing an entire RAM bank in Example 5-5. EXAMPLE 5-5: HOW TO CLEAR RAM (BANK 1) USING INDIRECT ADDRESSING Note: The execution of some instructions in the core PIC18 instruction set are changed when the PIC18 extended instruction set is enabled. See Section 5.6 “Data Memory and the Extended Instruction Set” for more information. LFSR FSR0, 100h ; NEXT CLRF POSTINC0 ; Clear INDF ; register then ; inc pointer BTFSS FSR0H, 1 ; All done with ; Bank1? BRA NEXT ; NO, clear next CONTINUE ; YES, continue © 2009 Microchip Technology Inc. DS39632E-page 75 PIC18F2455/2550/4455/4550 5.4.3.1 FSR Registers and the INDF Operand At the core of Indirect Addressing are three sets of registers: FSR0, FSR1 and FSR2. Each represents a pair of 8-bit registers: FSRnH and FSRnL. The four upper bits of the FSRnH register are not used, so each FSR pair holds a 12-bit value. This represents a value that can address the entire range of the data memory in a linear fashion. The FSR register pairs, then, serve as pointers to data memory locations. Indirect Addressing is accomplished with a set of Indirect File Operands, INDF0 through INDF2. These can be thought of as “virtual” registers; they are mapped in the SFR space but are not physically implemented. Reading or writing to a particular INDF register actually accesses its corresponding FSR register pair. A read from INDF1, for example, reads the data at the address indicated by FSR1H:FSR1L. Instructions that use the INDF registers as operands actually use the contents of their corresponding FSR as a pointer to the instruction’s target. The INDF operand is just a convenient way of using the pointer. Because Indirect Addressing uses a full 12-bit address, data RAM banking is not necessary. Thus, the current contents of the BSR and the Access RAM bit have no effect on determining the target address. FIGURE 5-7: INDIRECT ADDRESSING FSR1H:FSR1L 7 0 Data Memory 000h 100h 200h 300h F00h E00h FFFh Bank 0 Bank 1 Bank 2 Bank 14 Bank 15 Bank 3 through Bank 13 ADDWF, INDF1, 1 7 0 Using an instruction with one of the indirect addressing registers as the operand.... ...uses the 12-bit address stored in the FSR pair associated with that register.... ...to determine the data memory location to be used in that operation. In this case, the FSR1 pair contains ECCh. This means the contents of location ECCh will be added to that of the W register and stored back in ECCh. x x x x 1 1 1 0 1 1 0 0 1 1 0 0 PIC18F2455/2550/4455/4550 DS39632E-page 76 © 2009 Microchip Technology Inc. 5.4.3.2 FSR Registers and POSTINC, POSTDEC, PREINC and PLUSW In addition to the INDF operand, each FSR register pair also has four additional indirect operands. Like INDF, these are “virtual” registers that cannot be indirectly read or written to. Accessing these registers actually accesses the associated FSR register pair, but also performs a specific action on it stored value. They are: • POSTDEC: accesses the FSR value, then automatically decrements it by ‘1’ afterwards • POSTINC: accesses the FSR value, then automatically increments it by ‘1’ afterwards • PREINC: increments the FSR value by ‘1’, then uses it in the operation • PLUSW: adds the signed value of the W register (range of -127 to 128) to that of the FSR and uses the new value in the operation. In this context, accessing an INDF register uses the value in the FSR registers without changing them. Similarly, accessing a PLUSW register gives the FSR value offset by that in the W register; neither value is actually changed in the operation. Accessing the other virtual registers changes the value of the FSR registers. Operations on the FSRs with POSTDEC, POSTINC and PREINC affect the entire register pair; that is, rollovers of the FSRnL register, from FFh to 00h, carry over to the FSRnH register. On the other hand, results of these operations do not change the value of any flags in the STATUS register (e.g., Z, N, OV, etc.). The PLUSW register can be used to implement a form of Indexed Addressing in the data memory space. By manipulating the value in the W register, users can reach addresses that are fixed offsets from pointer addresses. In some applications, this can be used to implement some powerful program control structure, such as software stacks, inside of data memory. 5.4.3.3 Operations by FSRs on FSRs Indirect Addressing operations that target other FSRs or virtual registers represent special cases. For example, using an FSR to point to one of the virtual registers will not result in successful operations. As a specific case, assume that FSR0H:FSR0L contains FE7h, the address of INDF1. Attempts to read the value of INDF1, using INDF0 as an operand, will return 00h. Attempts to write to INDF1, using INDF0 as the operand, will result in a NOP. On the other hand, using the virtual registers to write to an FSR pair may not occur as planned. In these cases, the value will be written to the FSR pair but without any incrementing or decrementing. Thus, writing to INDF2 or POSTDEC2 will write the same value to the FSR2H:FSR2L. Since the FSRs are physical registers mapped in the SFR space, they can be manipulated through all direct operations. Users should proceed cautiously when working on these registers, particularly if their code uses Indirect Addressing. Similarly, operations by Indirect Addressing are generally permitted on all other SFRs. Users should exercise the appropriate caution that they do not inadvertently change settings that might affect the operation of the device. © 2009 Microchip Technology Inc. DS39632E-page 77 PIC18F2455/2550/4455/4550 5.5 Program Memory and the Extended Instruction Set The operation of program memory is unaffected by the use of the extended instruction set. Enabling the extended instruction set adds eight additional two-word commands to the existing PIC18 instruction set: ADDFSR, ADDULNK, CALLW, MOVSF, MOVSS, PUSHL, SUBFSR and SUBULNK. These instructions are executed as described in Section 5.2.4 “Two-Word Instructions”. 5.6 Data Memory and the Extended Instruction Set Enabling the PIC18 extended instruction set (XINST Configuration bit = 1) significantly changes certain aspects of data memory and its addressing. Specifically, the use of the Access Bank for many of the core PIC18 instructions is different. This is due to the introduction of a new addressing mode for the data memory space. This mode also alters the behavior of Indirect Addressing using FSR2 and its associated operands. What does not change is just as important. The size of the data memory space is unchanged, as well as its linear addressing. The SFR map remains the same. Core PIC18 instructions can still operate in both Direct and Indirect Addressing mode; inherent and literal instructions do not change at all. Indirect Addressing with FSR0 and FSR1 also remains unchanged. 5.6.1 INDEXED ADDRESSING WITH LITERAL OFFSET Enabling the PIC18 extended instruction set changes the behavior of Indirect Addressing using the FSR2 register pair and its associated file operands. Under the proper conditions, instructions that use the Access Bank – that is, most bit-oriented and byte-oriented instructions – can invoke a form of Indexed Addressing using an offset specified in the instruction. This special addressing mode is known as Indexed Addressing with Literal Offset or Indexed Literal Offset mode. When using the extended instruction set, this addressing mode requires the following: • The use of the Access Bank is forced (‘a’ = 0); and • The file address argument is less than or equal to 5Fh. Under these conditions, the file address of the instruction is not interpreted as the lower byte of an address (used with the BSR in Direct Addressing), or as an 8-bit address in the Access Bank. Instead, the value is interpreted as an offset value to an Address Pointer specified by FSR2. The offset and the contents of FSR2 are added to obtain the target address of the operation. 5.6.2 INSTRUCTIONS AFFECTED BY INDEXED LITERAL OFFSET MODE Any of the core PIC18 instructions that can use Direct Addressing are potentially affected by the Indexed Literal Offset Addressing mode. This includes all byte-oriented and bit-oriented instructions, or almost one-half of the standard PIC18 instruction set. Instructions that only use Inherent or Literal Addressing modes are unaffected. Additionally, byte-oriented and bit-oriented instructions are not affected if they do not use the Access Bank (Access RAM bit is ‘1’) or include a file address of 60h or above. Instructions meeting these criteria will continue to execute as before. A comparison of the different possible addressing modes when the extended instruction set is enabled in shown in Figure 5-8. Those who desire to use byte-oriented or bit-oriented instructions in the Indexed Literal Offset mode should note the changes to assembler syntax for this mode. This is described in more detail in Section 26.2.1 “Extended Instruction Syntax”. PIC18F2455/2550/4455/4550 DS39632E-page 78 © 2009 Microchip Technology Inc. FIGURE 5-8: COMPARING ADDRESSING OPTIONS FOR BIT-ORIENTED AND BYTE-ORIENTED INSTRUCTIONS (EXTENDED INSTRUCTION SET ENABLED) EXAMPLE INSTRUCTION: ADDWF, f, d, a (Opcode: 0010 01da ffff ffff) When a = 0 and f ≥ 60h: The instruction executes in Direct Forced mode. ‘f’ is interpreted as a location in the Access RAM between 060h and 0FFh. This is the same as the SFRs or locations F60h to 0FFh (Bank 15) of data memory. Locations below 60h are not available in this addressing mode. When a = 0 and f ≤ 5Fh: The instruction executes in Indexed Literal Offset mode. ‘f’ is interpreted as an offset to the address value in FSR2. The two are added together to obtain the address of the target register for the instruction. The address can be anywhere in the data memory space. Note that in this mode, the correct syntax is now: ADDWF [k], d where ‘k’ is the same as ‘f’. When a = 1 (all values of f): The instruction executes in Direct mode (also known as Direct Long mode). ‘f’ is interpreted as a location in one of the 16 banks of the data memory space. The bank is designated by the Bank Select Register (BSR). The address can be in any implemented bank in the data memory space. 000h 060h 100h F00h F60h FFFh Valid range 00h 60h FFh Data Memory Access RAM Bank 0 Bank 1 through Bank 14 Bank 15 SFRs 000h 080h 100h F00h F60h FFFh Data Memory Bank 0 Bank 1 through Bank 14 Bank 15 SFRs FSR2H FSR2L 001001da ffffffff 001001da ffffffff 000h 080h 100h F00h F60h FFFh Data Memory Bank 0 Bank 1 through Bank 14 Bank 15 SFRs for ‘f’ BSR 00000000 080h © 2009 Microchip Technology Inc. DS39632E-page 79 PIC18F2455/2550/4455/4550 5.6.3 MAPPING THE ACCESS BANK IN INDEXED LITERAL OFFSET MODE The use of Indexed Literal Offset Addressing mode effectively changes how the lower portion of Access RAM (00h to 5Fh) is mapped. Rather than containing just the contents of the bottom half of Bank 0, this mode maps the contents from Bank 0 and a user-defined “window” that can be located anywhere in the data memory space. The value of FSR2 establishes the lower boundary of the addresses mapped into the window, while the upper boundary is defined by FSR2 plus 95 (5Fh). Addresses in the Access RAM above 5Fh are mapped as previously described (see Section 5.3.3 “Access Bank”). An example of Access Bank remapping in this addressing mode is shown in Figure 5-9. Remapping of the Access Bank applies only to operations using the Indexed Literal Offset mode. Operations that use the BSR (Access RAM bit is ‘1’) will continue to use Direct Addressing as before. Any indirect or indexed operation that explicitly uses any of the indirect file operands (including FSR2) will continue to operate as standard Indirect Addressing. Any instruction that uses the Access Bank, but includes a register address of greater than 05Fh, will use Direct Addressing and the normal Access Bank map. 5.6.4 BSR IN INDEXED LITERAL OFFSET MODE Although the Access Bank is remapped when the extended instruction set is enabled, the operation of the BSR remains unchanged. Direct Addressing, using the BSR to select the data memory bank, operates in the same manner as previously described. FIGURE 5-9: REMAPPING THE ACCESS BANK WITH INDEXED LITERAL OFFSET ADDRESSING Data Memory 000h 100h 200h F60h F00h FFFh Bank 1 Bank 15 Bank 2 through Bank 14 SFRs ADDWF f, d, a FSR2H:FSR2L = 120h Locations in the region from the FSR2 Pointer (120h) to the pointer plus 05Fh (17Fh) are mapped to the bottom of the Access RAM (000h-05Fh). Special Function Registers at F60h through FFFh are mapped to 60h through FFh as usual. Bank 0 addresses below 5Fh are not available in this mode. They can still be addressed by using the BSR. Access Bank 00h 60h FFh Bank 0 SFRs Bank 1 “Window” Window Example Situation: 120h 17Fh 5Fh PIC18F2455/2550/4455/4550 DS39632E-page 80 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 81 PIC18F2455/2550/4455/4550 6.0 FLASH PROGRAM MEMORY The Flash program memory is readable, writable and erasable, during normal operation over the entire VDD range. A read from program memory is executed on one byte at a time. A write to program memory is executed on blocks of 32 bytes at a time. Program memory is erased in blocks of 64 bytes at a time. A Bulk Erase operation may not be issued from user code. Writing or erasing program memory will cease instruction fetches until the operation is complete. The program memory cannot be accessed during the write or erase, therefore, code cannot execute. An internal programming timer terminates program memory writes and erases. A value written to program memory does not need to be a valid instruction. Executing a program memory location that forms an invalid instruction results in a NOP. 6.1 Table Reads and Table Writes In order to read and write program memory, there are two operations that allow the processor to move bytes between the program memory space and the data RAM: • Table Read (TBLRD) • Table Write (TBLWT) The program memory space is 16 bits wide, while the data RAM space is 8 bits wide. Table reads and table writes move data between these two memory spaces through an 8-bit register (TABLAT). Table read operations retrieve data from program memory and place it into the data RAM space. Figure 6-1 shows the operation of a table read with program memory and data RAM. Table write operations store data from the data memory space into holding registers in program memory. The procedure to write the contents of the holding registers into program memory is detailed in Section 6.5 “Writing to Flash Program Memory”. Figure 6-2 shows the operation of a table write with program memory and data RAM. Table operations work with byte entities. A table block containing data, rather than program instructions, is not required to be word-aligned. Therefore, a table block can start and end at any byte address. If a table write is being used to write executable code into program memory, program instructions will need to be word-aligned. FIGURE 6-1: TABLE READ OPERATION Table Pointer(1) Table Latch (8-bit) Program Memory TBLPTRH TBLPTRL TABLAT TBLPTRU Instruction: TBLRD* Note 1: Table Pointer register points to a byte in program memory. Program Memory (TBLPTR) PIC18F2455/2550/4455/4550 DS39632E-page 82 © 2009 Microchip Technology Inc. FIGURE 6-2: TABLE WRITE OPERATION 6.2 Control Registers Several control registers are used in conjunction with the TBLRD and TBLWT instructions. These include the: • EECON1 register • EECON2 register • TABLAT register • TBLPTR registers 6.2.1 EECON1 AND EECON2 REGISTERS The EECON1 register (Register 6-1) is the control register for memory accesses. The EECON2 register is not a physical register; it is used exclusively in the memory write and erase sequences. Reading EECON2 will read all ‘0’s. The EEPGD control bit determines if the access will be a program or data EEPROM memory access. When clear, any subsequent operations will operate on the data EEPROM memory. When set, any subsequent operations will operate on the program memory. The CFGS control bit determines if the access will be to the Configuration/Calibration registers or to program memory/data EEPROM memory. When set, subsequent operations will operate on Configuration registers regardless of EEPGD (see Section 25.0 “Special Features of the CPU”). When clear, memory selection access is determined by EEPGD. The FREE bit, when set, will allow a program memory erase operation. When FREE is set, the erase operation is initiated on the next WR command. When FREE is clear, only writes are enabled. The WREN bit, when set, will allow a write operation. On power-up, the WREN bit is clear. The WRERR bit is set in hardware when the WREN bit is set and cleared when the internal programming timer expires and the write operation is complete. The WR control bit initiates write operations. The bit cannot be cleared, only set, in software; it is cleared in hardware at the completion of the write operation. Table Pointer(1) Table Latch (8-bit) TBLPTRH TBLPTRL TABLAT Program Memory (TBLPTR) TBLPTRU Instruction: TBLWT* Note 1: Table Pointer actually points to one of 32 holding registers, the address of which is determined by TBLPTRL<4:0>. The process for physically writing data to the program memory array is discussed in Section 6.5 “Writing to Flash Program Memory”. Holding Registers Program Memory Note: During normal operation, the WRERR is read as ‘1’. This can indicate that a write operation was prematurely terminated by a Reset or a write operation was attempted improperly. Note: The EEIF interrupt flag bit (PIR2<4>) is set when the write is complete. It must be cleared in software. © 2009 Microchip Technology Inc. DS39632E-page 83 PIC18F2455/2550/4455/4550 REGISTER 6-1: EECON1: DATA EEPROM CONTROL REGISTER 1 R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0 EEPGD CFGS — FREE WRERR(1) WREN WR RD bit 7 bit 0 Legend: S = Settable bit R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit 1 = Access Flash program memory 0 = Access data EEPROM memory bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit 1 = Access Configuration registers 0 = Access Flash program or data EEPROM memory bit 5 Unimplemented: Read as ‘0’ bit 4 FREE: Flash Row Erase Enable bit 1 = Erase the program memory row addressed by TBLPTR on the next WR command (cleared by completion of erase operation) 0 = Perform write-only bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit(1) 1 = A write operation is prematurely terminated (any Reset during self-timed programming in normal operation or an improper write attempt) 0 = The write operation completed bit 2 WREN: Flash Program/Data EEPROM Write Enable bit 1 = Allows write cycles to Flash program/data EEPROM 0 = Inhibits write cycles to Flash program/data EEPROM bit 1 WR: Write Control bit 1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle (The operation is self-timed and the bit is cleared by hardware once write is complete. The WR bit can only be set (not cleared) in software.) 0 = Write cycle to the EEPROM is complete bit 0 RD: Read Control bit 1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit can only be set (not cleared) in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.) 0 = Does not initiate an EEPROM read Note 1: When a WRERR occurs, the EEPGD and CFGS bits are not cleared. This allows tracing of the error condition. PIC18F2455/2550/4455/4550 DS39632E-page 84 © 2009 Microchip Technology Inc. 6.2.2 TABLE LATCH REGISTER (TABLAT) The Table Latch (TABLAT) is an 8-bit register mapped into the SFR space. The Table Latch register is used to hold 8-bit data during data transfers between program memory and data RAM. 6.2.3 TABLE POINTER REGISTER (TBLPTR) The Table Pointer (TBLPTR) register addresses a byte within the program memory. The TBLPTR is comprised of three SFR registers: Table Pointer Upper Byte, Table Pointer High Byte and Table Pointer Low Byte (TBLPTRU:TBLPTRH:TBLPTRL). These three registers join to form a 22-bit wide pointer. The low-order 21 bits allow the device to address up to 2 Mbytes of program memory space. The 22nd bit allows access to the Device ID, the user ID and the Configuration bits. The Table Pointer, TBLPTR, is used by the TBLRD and TBLWT instructions. These instructions can update the TBLPTR in one of four ways based on the table operation. These operations are shown in Table 6-1. These operations on the TBLPTR only affect the low-order 21 bits. 6.2.4 TABLE POINTER BOUNDARIES TBLPTR is used in reads, writes and erases of the Flash program memory. When a TBLRD is executed, all 22 bits of the TBLPTR determine which byte is read from program memory into TABLAT. When a TBLWT is executed, the five LSbs of the Table Pointer register (TBLPTR<4:0>) determine which of the 32 program memory holding registers is written to. When the timed write to program memory begins (via the WR bit), the 16 MSbs of the TBLPTR (TBLPTR<21:6>) determine which program memory block of 32 bytes is written to. For more detail, see Section 6.5 “Writing to Flash Program Memory”. When an erase of program memory is executed, the 16 MSbs of the Table Pointer register (TBLPTR<21:6>) point to the 64-byte block that will be erased. The Least Significant bits (TBLPTR<5:0>) are ignored. Figure 6-3 describes the relevant boundaries of the TBLPTR based on Flash program memory operations. TABLE 6-1: TABLE POINTER OPERATIONS WITH TBLRD AND TBLWT INSTRUCTIONS FIGURE 6-3: TABLE POINTER BOUNDARIES BASED ON OPERATION Example Operation on Table Pointer TBLRD* TBLWT* TBLPTR is not modified TBLRD*+ TBLWT*+ TBLPTR is incremented after the read/write TBLRD*- TBLWT*- TBLPTR is decremented after the read/write TBLRD+* TBLWT+* TBLPTR is incremented before the read/write 21 16 15 8 7 0 TABLE ERASE TABLE READ – TBLPTR<21:0> TBLPTRU TBLPTRH TBLPTRL TBLPTR<21:6> TABLE WRITE – TBLPTR<21:5> © 2009 Microchip Technology Inc. DS39632E-page 85 PIC18F2455/2550/4455/4550 6.3 Reading the Flash Program Memory The TBLRD instruction is used to retrieve data from program memory and places it into data RAM. Table reads from program memory are performed one byte at a time. TBLPTR points to a byte address in program space. Executing TBLRD places the byte pointed to into TABLAT. In addition, TBLPTR can be modified automatically for the next table read operation. The internal program memory is typically organized by words. The Least Significant bit of the address selects between the high and low bytes of the word. Figure 6-4 shows the interface between the internal program memory and the TABLAT. FIGURE 6-4: READS FROM FLASH PROGRAM MEMORY EXAMPLE 6-1: READING A FLASH PROGRAM MEMORY WORD (Even Byte Address) Program Memory (Odd Byte Address) TBLRD TABLAT TBLPTR = xxxxx1 FETCH Instruction Register (IR) Read Register TBLPTR = xxxxx0 MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base MOVWF TBLPTRU ; address of the word MOVLW CODE_ADDR_HIGH MOVWF TBLPTRH MOVLW CODE_ADDR_LOW MOVWF TBLPTRL READ_WORD TBLRD*+ ; read into TABLAT and increment MOVF TABLAT, W ; get data MOVWF WORD_EVEN TBLRD*+ ; read into TABLAT and increment MOVF TABLAT, W ; get data MOVF WORD_ODD PIC18F2455/2550/4455/4550 DS39632E-page 86 © 2009 Microchip Technology Inc. 6.4 Erasing Flash Program Memory The minimum erase block is 32 words or 64 bytes. Only through the use of an external programmer, or through ICSP control, can larger blocks of program memory be Bulk Erased. Word Erase in the Flash array is not supported. When initiating an erase sequence from the microcontroller itself, a block of 64 bytes of program memory is erased. The Most Significant 16 bits of the TBLPTR<21:6> point to the block being erased. TBLPTR<5:0> are ignored. The EECON1 register commands the erase operation. The EEPGD bit must be set to point to the Flash program memory. The WREN bit must be set to enable write operations. The FREE bit is set to select an erase operation. For protection, the write initiate sequence for EECON2 must be used. A long write is necessary for erasing the internal Flash. Instruction execution is halted while in a long write cycle. The long write will be terminated by the internal programming timer. 6.4.1 FLASH PROGRAM MEMORY ERASE SEQUENCE The sequence of events for erasing a block of internal program memory is: 1. Load Table Pointer register with address of row being erased. 2. Set the EECON1 register for the erase operation: • set EEPGD bit to point to program memory; • clear the CFGS bit to access program memory; • set WREN bit to enable writes; • set FREE bit to enable the erase. 3. Disable interrupts. 4. Write 55h to EECON2. 5. Write 0AAh to EECON2. 6. Set the WR bit. This will begin the Row Erase cycle. 7. The CPU will stall for duration of the erase (about 2 ms using internal timer). 8. Re-enable interrupts. EXAMPLE 6-2: ERASING A FLASH PROGRAM MEMORY ROW MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base MOVWF TBLPTRU ; address of the memory block MOVLW CODE_ADDR_HIGH MOVWF TBLPTRH MOVLW CODE_ADDR_LOW MOVWF TBLPTRL ERASE_ROW BSF EECON1, EEPGD ; point to Flash program memory BCF EECON1, CFGS ; access Flash program memory BSF EECON1, WREN ; enable write to memory BSF EECON1, FREE ; enable Row Erase operation BCF INTCON, GIE ; disable interrupts Required MOVLW 55h Sequence MOVWF EECON2 ; write 55h MOVLW 0AAh MOVWF EECON2 ; write 0AAh BSF EECON1, WR ; start erase (CPU stall) BSF INTCON, GIE ; re-enable interrupts © 2009 Microchip Technology Inc. DS39632E-page 87 PIC18F2455/2550/4455/4550 6.5 Writing to Flash Program Memory The minimum programming block is 16 words or 32 bytes. Word or byte programming is not supported. Table writes are used internally to load the holding registers needed to program the Flash memory. There are 32 holding registers used by the table writes for programming. Since the Table Latch (TABLAT) is only a single byte, the TBLWT instruction may need to be executed 32 times for each programming operation. All of the table write operations will essentially be short writes because only the holding registers are written. At the end of updating the 32 holding registers, the EECON1 register must be written to in order to start the programming operation with a long write. The long write is necessary for programming the internal Flash. Instruction execution is halted while in a long write cycle. The long write will be terminated by the internal programming timer. The EEPROM on-chip timer controls the write time. The write/erase voltages are generated by an on-chip charge pump, rated to operate over the voltage range of the device. FIGURE 6-5: TABLE WRITES TO FLASH PROGRAM MEMORY 6.5.1 FLASH PROGRAM MEMORY WRITE SEQUENCE The sequence of events for programming an internal program memory location should be: 1. Read 64 bytes into RAM. 2. Update data values in RAM as necessary. 3. Load Table Pointer register with address being erased. 4. Execute the Row Erase procedure. 5. Load Table Pointer register with address of first byte being written. 6. Write 32 bytes into the holding registers with auto-increment. 7. Set the EECON1 register for the write operation: • set EEPGD bit to point to program memory; • clear the CFGS bit to access program memory; • set WREN to enable byte writes. 8. Disable interrupts. 9. Write 55h to EECON2. 10. Write 0AAh to EECON2. 11. Set the WR bit. This will begin the write cycle. 12. The CPU will stall for duration of the write (about 2 ms using internal timer). 13. Re-enable interrupts. 14. Repeat steps 6 through 14 once more to write 64 bytes. 15. Verify the memory (table read). This procedure will require about 8 ms to update one row of 64 bytes of memory. An example of the required code is given in Example 6-3. Note: The default value of the holding registers on device Resets and after write operations is FFh. A write of FFh to a holding register does not modify that byte. This means that individual bytes of program memory may be modified, provided that the change does not attempt to change any bit from a ‘0’ to a ‘1’. When modifying individual bytes, it is not necessary to load all 32 holding registers before executing a write operation. TBLPTR = xxxx00 TBLPTR = xxxx01 TBLPTR = xxxx02 TBLPTR = xxxx1F Program Memory Holding Register Holding Register Holding Register Holding Register 8 8 8 8 TABLAT Write Register Note: Before setting the WR bit, the Table Pointer address needs to be within the intended address range of the 32 bytes in the holding register. PIC18F2455/2550/4455/4550 DS39632E-page 88 © 2009 Microchip Technology Inc. EXAMPLE 6-3: WRITING TO FLASH PROGRAM MEMORY MOVLW D'64’ ; number of bytes in erase block MOVWF COUNTER MOVLW BUFFER_ADDR_HIGH ; point to buffer MOVWF FSR0H MOVLW BUFFER_ADDR_LOW MOVWF FSR0L MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base MOVWF TBLPTRU ; address of the memory block MOVLW CODE_ADDR_HIGH MOVWF TBLPTRH MOVLW CODE_ADDR_LOW MOVWF TBLPTRL READ_BLOCK TBLRD*+ ; read into TABLAT, and inc MOVF TABLAT, W ; get data MOVWF POSTINC0 ; store data DECFSZ COUNTER ; done? BRA READ_BLOCK ; repeat MODIFY_WORD MOVLW DATA_ADDR_HIGH ; point to buffer MOVWF FSR0H MOVLW DATA_ADDR_LOW MOVWF FSR0L MOVLW NEW_DATA_LOW ; update buffer word MOVWF POSTINC0 MOVLW NEW_DATA_HIGH MOVWF INDF0 ERASE_BLOCK MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base MOVWF TBLPTRU ; address of the memory block MOVLW CODE_ADDR_HIGH MOVWF TBLPTRH MOVLW CODE_ADDR_LOW MOVWF TBLPTRL BSF EECON1, EEPGD ; point to Flash program memory BCF EECON1, CFGS ; access Flash program memory BSF EECON1, WREN ; enable write to memory BSF EECON1, FREE ; enable Row Erase operation BCF INTCON, GIE ; disable interrupts MOVLW 55h Required MOVWF EECON2 ; write 55h Sequence MOVLW 0AAh MOVWF EECON2 ; write 0AAh BSF EECON1, WR ; start erase (CPU stall) BSF INTCON, GIE ; re-enable interrupts TBLRD*- ; dummy read decrement MOVLW BUFFER_ADDR_HIGH ; point to buffer MOVWF FSR0H MOVLW BUFFER_ADDR_LOW MOVWF FSR0L MOVLW D’2’ MOVWF COUNTER1 WRITE_BUFFER_BACK MOVLW D’32’ ; number of bytes in holding register MOVWF COUNTER WRITE_BYTE_TO_HREGS MOVF POSTINC0, W ; get low byte of buffer data MOVWF TABLAT ; present data to table latch TBLWT+* ; write data, perform a short write ; to internal TBLWT holding register. DECFSZ COUNTER ; loop until buffers are full BRA WRITE_WORD_TO_HREGS © 2009 Microchip Technology Inc. DS39632E-page 89 PIC18F2455/2550/4455/4550 EXAMPLE 6-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED) 6.5.2 WRITE VERIFY Depending on the application, good programming practice may dictate that the value written to the memory should be verified against the original value. This should be used in applications where excessive writes can stress bits near the specification limit. 6.5.3 UNEXPECTED TERMINATION OF WRITE OPERATION If a write is terminated by an unplanned event, such as loss of power or an unexpected Reset, the memory location just programmed should be verified and reprogrammed if needed. If the write operation is interrupted by a MCLR Reset or a WDT Time-out Reset during normal operation, the user can check the WRERR bit and rewrite the location(s) as needed. 6.5.4 PROTECTION AGAINST SPURIOUS WRITES To protect against spurious writes to Flash program memory, the write initiate sequence must also be followed. See Section 25.0 “Special Features of the CPU” for more detail. 6.6 Flash Program Operation During Code Protection See Section 25.5 “Program Verification and Code Protection” for details on code protection of Flash program memory. TABLE 6-2: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY PROGRAM_MEMORY BSF EECON1, EEPGD ; point to Flash program memory BCF EECON1, CFGS ; access Flash program memory BSF EECON1, WREN ; enable write to memory BCF INTCON, GIE ; disable interrupts MOVLW 55h Required MOVWF EECON2 ; write 55h Sequence MOVLW 0AAh MOVWF EECON2 ; write 0AAh BSF EECON1, WR ; start program (CPU stall) DECFSZ COUNTER1 BRA WRITE_BUFFER_BACK BSF INTCON, GIE ; re-enable interrupts BCF EECON1, WREN ; disable write to memory Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page TBLPTRU — — bit 21(1) Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) 53 TBLPTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 53 TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 53 TABLAT Program Memory Table Latch 53 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 EECON2 EEPROM Control Register 2 (not a physical register) 55 EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 55 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access. Note 1: Bit 21 of the TBLPTRU allows access to the device Configuration bits. PIC18F2455/2550/4455/4550 DS39632E-page 90 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 91 PIC18F2455/2550/4455/4550 7.0 DATA EEPROM MEMORY The data EEPROM is a nonvolatile memory array, separate from the data RAM and program memory, that is used for long-term storage of program data. It is not directly mapped in either the register file or program memory space, but is indirectly addressed through the Special Function Registers (SFRs). The EEPROM is readable and writable during normal operation over the entire VDD range. Four SFRs are used to read and write to the data EEPROM as well as the program memory. They are: • EECON1 • EECON2 • EEDATA • EEADR The data EEPROM allows byte read and write. When interfacing to the data memory block, EEDATA holds the 8-bit data for read/write and the EEADR register holds the address of the EEPROM location being accessed. The EEPROM data memory is rated for high erase/write cycle endurance. A byte write automatically erases the location and writes the new data (erase-before-write). The write time is controlled by an on-chip timer; it will vary with voltage and temperature as well as from chip to chip. Please refer to parameter D122 (Table 28-1 in Section 28.0 “Electrical Characteristics”) for exact limits. 7.1 EECON1 and EECON2 Registers Access to the data EEPROM is controlled by two registers: EECON1 and EECON2. These are the same registers which control access to the program memory and are used in a similar manner for the data EEPROM. The EECON1 register (Register 7-1) is the control register for data and program memory access. Control bit, EEPGD, determines if the access will be to program or data EEPROM memory. When clear, operations will access the data EEPROM memory. When set, program memory is accessed. Control bit, CFGS, determines if the access will be to the Configuration registers or to program memory/data EEPROM memory. When set, subsequent operations access Configuration registers. When CFGS is clear, the EEPGD bit selects either Flash program or data EEPROM memory. The WREN bit, when set, will allow a write operation. On power-up, the WREN bit is clear. The WRERR bit is set in hardware when the WREN bit is set and cleared when the internal programming timer expires and the write operation is complete. The WR control bit initiates write operations. The bit cannot be cleared, only set, in software; it is cleared in hardware at the completion of the write operation. Control bits, RD and WR, start read and erase/write operations, respectively. These bits are set by firmware and cleared by hardware at the completion of the operation. The RD bit cannot be set when accessing program memory (EEPGD = 1). Program memory is read using table read instructions. See Section 6.1 “Table Reads and Table Writes” regarding table reads. The EECON2 register is not a physical register. It is used exclusively in the memory write and erase sequences. Reading EECON2 will read all ‘0’s. Note: During normal operation, the WRERR is read as ‘1’. This can indicate that a write operation was prematurely terminated by a Reset or a write operation was attempted improperly. Note: The EEIF interrupt flag bit (PIR2<4>) is set when the write is complete. It must be cleared in software. PIC18F2455/2550/4455/4550 DS39632E-page 92 © 2009 Microchip Technology Inc. REGISTER 7-1: EECON1: DATA EEPROM CONTROL REGISTER 1 R/W-x R/W-x U-0 R/W-0 R/W-x R/W-0 R/S-0 R/S-0 EEPGD CFGS — FREE WRERR(1) WREN WR RD bit 7 bit 0 Legend: S = Settable bit R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit 1 = Access Flash program memory 0 = Access data EEPROM memory bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit 1 = Access Configuration registers 0 = Access Flash program or data EEPROM memory bit 5 Unimplemented: Read as ‘0’ bit 4 FREE: Flash Row Erase Enable bit 1 = Erase the program memory row addressed by TBLPTR on the next WR command (cleared by completion of erase operation) 0 = Perform write-only bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit(1) 1 = A write operation is prematurely terminated (any Reset during self-timed programming in normal operation or an improper write attempt) 0 = The write operation completed bit 2 WREN: Flash Program/Data EEPROM Write Enable bit 1 = Allows write cycles to Flash program/data EEPROM 0 = Inhibits write cycles to Flash program/data EEPROM bit 1 WR: Write Control bit 1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle (The operation is self-timed and the bit is cleared by hardware once write is complete. The WR bit can only be set (not cleared) in software.) 0 = Write cycle to the EEPROM is complete bit 0 RD: Read Control bit 1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared in hardware. The RD bit can only be set (not cleared) in software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.) 0 = Does not initiate an EEPROM read Note 1: When a WRERR occurs, the EEPGD and CFGS bits are not cleared. This allows tracing of the error condition. © 2009 Microchip Technology Inc. DS39632E-page 93 PIC18F2455/2550/4455/4550 7.2 Reading the Data EEPROM Memory To read a data memory location, the user must write the address to the EEADR register, clear the EEPGD control bit (EECON1<7>) and then set control bit, RD (EECON1<0>). The data is available on the very next instruction cycle; therefore, the EEDATA register can be read by the next instruction. EEDATA will hold this value until another read operation or until it is written to by the user (during a write operation). The basic process is shown in Example 7-1. 7.3 Writing to the Data EEPROM Memory To write an EEPROM data location, the address must first be written to the EEADR register and the data written to the EEDATA register. The sequence in Example 7-2 must be followed to initiate the write cycle. The write will not begin if this sequence is not exactly followed (write 55h to EECON2, write 0AAh to EECON2, then set WR bit) for each byte. It is strongly recommended that interrupts be disabled during this code segment. Additionally, the WREN bit in EECON1 must be set to enable writes. This mechanism prevents accidental writes to data EEPROM due to unexpected code execution (i.e., runaway programs). The WREN bit should be kept clear at all times except when updating the EEPROM. The WREN bit is not cleared by hardware. After a write sequence has been initiated, EECON1, EEADR and EEDATA cannot be modified. The WR bit will be inhibited from being set unless the WREN bit is set. The WREN bit must be set on a previous instruction. Both WR and WREN cannot be set with the same instruction. At the completion of the write cycle, the WR bit is cleared in hardware and the EEPROM Interrupt Flag bit (EEIF) is set. The user may either enable this interrupt, or poll this bit. EEIF must be cleared by software. 7.4 Write Verify Depending on the application, good programming practice may dictate that the value written to the memory should be verified against the original value. This should be used in applications where excessive writes can stress bits near the specification limit. EXAMPLE 7-1: DATA EEPROM READ EXAMPLE 7-2: DATA EEPROM WRITE MOVLW DATA_EE_ADDR ; MOVWF EEADR ; Lower bits of Data Memory Address to read BCF EECON1, EEPGD ; Point to DATA memory BCF EECON1, CFGS ; Access EEPROM BSF EECON1, RD ; EEPROM Read MOVF EEDATA, W ; W = EEDATA MOVLW DATA_EE_ADDR ; MOVWF EEADR ; Lower bits of Data Memory Address to write MOVLW DATA_EE_DATA ; MOVWF EEDATA ; Data Memory Value to write BCF EECON1, EEPGD ; Point to DATA memory BCF EECON1, CFGS ; Access EEPROM BSF EECON1, WREN ; Enable writes BCF INTCON, GIE ; Disable Interrupts MOVLW 55h ; Required MOVWF EECON2 ; Write 55h Sequence MOVLW 0AAh ; MOVWF EECON2 ; Write 0AAh BSF EECON1, WR ; Set WR bit to begin write BSF INTCON, GIE ; Enable Interrupts ; User code execution BCF EECON1, WREN ; Disable writes on write complete (EEIF set) PIC18F2455/2550/4455/4550 DS39632E-page 94 © 2009 Microchip Technology Inc. 7.5 Operation During Code-Protect Data EEPROM memory has its own code-protect bits in Configuration Words. External read and write operations are disabled if code protection is enabled. The microcontroller itself can both read and write to the internal data EEPROM regardless of the state of the code-protect Configuration bit. Refer to Section 25.0 “Special Features of the CPU” for additional information. 7.6 Protection Against Spurious Write There are conditions when the device may not want to write to the data EEPROM memory. To protect against spurious EEPROM writes, various mechanisms have been implemented. On power-up, the WREN bit is cleared. In addition, writes to the EEPROM are blocked during the Power-up Timer period (TPWRT, parameter 33, Table 28-12). The write initiate sequence and the WREN bit together help prevent an accidental write during brown-out, power glitch or software malfunction. 7.7 Using the Data EEPROM The data EEPROM is a high-endurance, byteaddressable array that has been optimized for the storage of frequently changing information (e.g., program variables or other data that are updated often). Frequently changing values will typically be updated more often than specification D124 or D124A. If this is not the case, an array refresh must be performed. For this reason, variables that change infrequently (such as constants, IDs, calibration, etc.) should be stored in Flash program memory. A simple data EEPROM refresh routine is shown in Example 7-3. EXAMPLE 7-3: DATA EEPROM REFRESH ROUTINE Note: If data EEPROM is only used to store constants and/or data that changes rarely, an array refresh is likely not required. See specification D124 or D124A. CLRF EEADR ; Start at address 0 BCF EECON1, CFGS ; Set for memory BCF EECON1, EEPGD ; Set for Data EEPROM BCF INTCON, GIE ; Disable interrupts BSF EECON1, WREN ; Enable writes Loop ; Loop to refresh array BSF EECON1, RD ; Read current address MOVLW 55h ; Required MOVWF EECON2 ; Write 55h Sequence MOVLW 0AAh ; MOVWF EECON2 ; Write 0AAh BSF EECON1, WR ; Set WR bit to begin write BTFSC EECON1, WR ; Wait for write to complete BRA $-2 INCFSZ EEADR, F ; Increment address BRA LOOP ; Not zero, do it again BCF EECON1, WREN ; Disable writes BSF INTCON, GIE ; Enable interrupts © 2009 Microchip Technology Inc. DS39632E-page 95 PIC18F2455/2550/4455/4550 TABLE 7-1: REGISTERS ASSOCIATED WITH DATA EEPROM MEMORY Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 EEADR EEPROM Address Register 55 EEDATA EEPROM Data Register 55 EECON2 EEPROM Control Register 2 (not a physical register) 55 EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 55 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access. PIC18F2455/2550/4455/4550 DS39632E-page 96 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 97 PIC18F2455/2550/4455/4550 8.0 8 x 8 HARDWARE MULTIPLIER 8.1 Introduction All PIC18 devices include an 8 x 8 hardware multiplier as part of the ALU. The multiplier performs an unsigned operation and yields a 16-bit result that is stored in the product register pair, PRODH:PRODL. The multiplier’s operation does not affect any flags in the STATUS register. Making multiplication a hardware operation allows it to be completed in a single instruction cycle. This has the advantages of higher computational throughput and reduced code size for multiplication algorithms and allows the PIC18 devices to be used in many applications previously reserved for digital signal processors. A comparison of various hardware and software multiply operations, along with the savings in memory and execution time, is shown in Table 8-1. 8.2 Operation Example 8-1 shows the instruction sequence for an 8 x 8 unsigned multiplication. Only one instruction is required when one of the arguments is already loaded in the WREG register. Example 8-2 shows the sequence to do an 8 x 8 signed multiplication. To account for the sign bits of the arguments, each argument’s Most Significant bit (MSb) is tested and the appropriate subtractions are done. EXAMPLE 8-1: 8 x 8 UNSIGNED MULTIPLY ROUTINE EXAMPLE 8-2: 8 x 8 SIGNED MULTIPLY ROUTINE TABLE 8-1: PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS MOVF ARG1, W ; MULWF ARG2 ; ARG1 * ARG2 -> ; PRODH:PRODL MOVF ARG1, W MULWF ARG2 ; ARG1 * ARG2 -> ; PRODH:PRODL BTFSC ARG2, SB ; Test Sign Bit SUBWF PRODH, F ; PRODH = PRODH ; - ARG1 MOVF ARG2, W BTFSC ARG1, SB ; Test Sign Bit SUBWF PRODH, F ; PRODH = PRODH ; - ARG2 Routine Multiply Method Program Memory (Words) Cycles (Max) Time @ 40 MHz @ 10 MHz @ 4 MHz 8 x 8 unsigned Without hardware multiply 13 69 6.9 μs 27.6 μs 69 μs Hardware multiply 1 1 100 ns 400 ns 1 μs 8 x 8 signed Without hardware multiply 33 91 9.1 μs 36.4 μs 91 μs Hardware multiply 6 6 600 ns 2.4 μs 6 μs 16 x 16 unsigned Without hardware multiply 21 242 24.2 μs 96.8 μs 242 μs Hardware multiply 28 28 2.8 μs 11.2 μs 28 μs 16 x 16 signed Without hardware multiply 52 254 25.4 μs 102.6 μs 254 μs Hardware multiply 35 40 4.0 μs 16.0 μs 40 μs PIC18F2455/2550/4455/4550 DS39632E-page 98 © 2009 Microchip Technology Inc. Example 8-3 shows the sequence to do a 16 x 16 unsigned multiplication. Equation 8-1 shows the algorithm that is used. The 32-bit result is stored in four registers (RES3:RES0). EQUATION 8-1: 16 x 16 UNSIGNED MULTIPLICATION ALGORITHM EXAMPLE 8-3: 16 x 16 UNSIGNED MULTIPLY ROUTINE Example 8-4 shows the sequence to do a 16 x 16 signed multiply. Equation 8-2 shows the algorithm used. The 32-bit result is stored in four registers (RES3:RES0). To account for the sign bits of the arguments, the MSb for each argument pair is tested and the appropriate subtractions are done. EQUATION 8-2: 16 x 16 SIGNED MULTIPLICATION ALGORITHM EXAMPLE 8-4: 16 x 16 SIGNED MULTIPLY ROUTINE RES3:RES0 = ARG1H:ARG1L • ARG2H:ARG2L = (ARG1H • ARG2H • 216) + (ARG1H • ARG2L • 28) + (ARG1L • ARG2H • 28) + (ARG1L • ARG2L) MOVF ARG1L, W MULWF ARG2L ; ARG1L * ARG2L-> ; PRODH:PRODL MOVFF PRODH, RES1 ; MOVFF PRODL, RES0 ; ; MOVF ARG1H, W MULWF ARG2H ; ARG1H * ARG2H-> ; PRODH:PRODL MOVFF PRODH, RES3 ; MOVFF PRODL, RES2 ; ; MOVF ARG1L, W MULWF ARG2H ; ARG1L * ARG2H-> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; MOVF ARG1H, W ; MULWF ARG2L ; ARG1H * ARG2L-> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; RES3:RES0 = ARG1H:ARG1L • ARG2H:ARG2L = (ARG1H • ARG2H • 216) + (ARG1H • ARG2L • 28) + (ARG1L • ARG2H • 28) + (ARG1L • ARG2L) + (-1 • ARG2H<7> • ARG1H:ARG1L • 216) + (-1 • ARG1H<7> • ARG2H:ARG2L • 216) MOVF ARG1L, W MULWF ARG2L ; ARG1L * ARG2L -> ; PRODH:PRODL MOVFF PRODH, RES1 ; MOVFF PRODL, RES0 ; ; MOVF ARG1H, W MULWF ARG2H ; ARG1H * ARG2H -> ; PRODH:PRODL MOVFF PRODH, RES3 ; MOVFF PRODL, RES2 ; ; MOVF ARG1L,W MULWF ARG2H ; ARG1L * ARG2H -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; MOVF ARG1H, W ; MULWF ARG2L ; ARG1H * ARG2L -> ; PRODH:PRODL MOVF PRODL, W ; ADDWF RES1, F ; Add cross MOVF PRODH, W ; products ADDWFC RES2, F ; CLRF WREG ; ADDWFC RES3, F ; ; BTFSS ARG2H, 7 ; ARG2H:ARG2L neg? BRA SIGN_ARG1 ; no, check ARG1 MOVF ARG1L, W ; SUBWF RES2 ; MOVF ARG1H, W ; SUBWFB RES3 ; SIGN_ARG1 BTFSS ARG1H, 7 ; ARG1H:ARG1L neg? BRA CONT_CODE ; no, done MOVF ARG2L, W ; SUBWF RES2 ; MOVF ARG2H, W ; SUBWFB RES3 ; CONT_CODE : © 2009 Microchip Technology Inc. DS39632E-page 99 PIC18F2455/2550/4455/4550 9.0 INTERRUPTS The PIC18F2455/2550/4455/4550 devices have multiple interrupt sources and an interrupt priority feature that allows each interrupt source to be assigned a highpriority level or a low-priority level. The high-priority interrupt vector is at 000008h and the low-priority interrupt vector is at 000018h. High-priority interrupt events will interrupt any low-priority interrupts that may be in progress. There are ten registers which are used to control interrupt operation. These registers are: • RCON • INTCON • INTCON2 • INTCON3 • PIR1, PIR2 • PIE1, PIE2 • IPR1, IPR2 It is recommended that the Microchip header files supplied with MPLAB® IDE be used for the symbolic bit names in these registers. This allows the assembler/ compiler to automatically take care of the placement of these bits within the specified register. Each interrupt source has three bits to control its operation. The functions of these bits are: • Flag bit to indicate that an interrupt event occurred • Enable bit that allows program execution to branch to the interrupt vector address when the flag bit is set • Priority bit to select high priority or low priority The interrupt priority feature is enabled by setting the IPEN bit (RCON<7>). When interrupt priority is enabled, there are two bits which enable interrupts globally. Setting the GIEH bit (INTCON<7>) enables all interrupts that have the priority bit set (high priority). Setting the GIEL bit (INTCON<6>) enables all interrupts that have the priority bit cleared (low priority). When the interrupt flag, enable bit and appropriate global interrupt enable bit are set, the interrupt will vector immediately to address 000008h or 000018h, depending on the priority bit setting. Individual interrupts can be disabled through their corresponding enable bits. When the IPEN bit is cleared (default state), the interrupt priority feature is disabled and interrupts are compatible with PIC® mid-range devices. In Compatibility mode, the interrupt priority bits for each source have no effect. INTCON<6> is the PEIE bit which enables/disables all peripheral interrupt sources. INTCON<7> is the GIE bit which enables/disables all interrupt sources. All interrupts branch to address 000008h in Compatibility mode. When an interrupt is responded to, the global interrupt enable bit is cleared to disable further interrupts. If the IPEN bit is cleared, this is the GIE bit. If interrupt priority levels are used, this will be either the GIEH or GIEL bit. High-priority interrupt sources can interrupt a lowpriority interrupt. Low-priority interrupts are not processed while high-priority interrupts are in progress. The return address is pushed onto the stack and the PC is loaded with the interrupt vector address (000008h or 000018h). Once in the Interrupt Service Routine, the source(s) of the interrupt can be determined by polling the interrupt flag bits. The interrupt flag bits must be cleared in software before re-enabling interrupts to avoid recursive interrupts. The “return from interrupt” instruction, RETFIE, exits the interrupt routine and sets the GIE bit (GIEH or GIEL if priority levels are used) which re-enables interrupts. For external interrupt events, such as the INTx pins or the PORTB input change interrupt, the interrupt latency will be three to four instruction cycles. The exact latency is the same for one or two-cycle instructions. Individual interrupt flag bits are set regardless of the status of their corresponding enable bit or the GIE bit. 9.1 USB Interrupts Unlike other peripherals, the USB module is capable of generating a wide range of interrupts for many types of events. These include several types of normal communication and status events and several module level error events. To handle these events, the USB module is equipped with its own interrupt logic. The logic functions in a manner similar to the microcontroller level interrupt funnel, with each interrupt source having separate flag and enable bits. All events are funneled to a single device level interrupt, USBIF (PIR2<5>). Unlike the device level interrupt logic, the individual USB interrupt events cannot be individually assigned their own priority. This is determined at the device level interrupt funnel for all USB events by the USBIP bit. For additional details on USB interrupt logic, refer to Section 17.5 “USB Interrupts”. Note: Do not use the MOVFF instruction to modify any of the interrupt control registers while any interrupt is enabled. Doing so may cause erratic microcontroller behavior. PIC18F2455/2550/4455/4550 DS39632E-page 100 © 2009 Microchip Technology Inc. FIGURE 9-1: INTERRUPT LOGIC TMR0IE GIE/GIEH PEIE/GIEL Wake-up if in Sleep Mode Interrupt to CPU Vector to Location 0008h INT2IF INT2IE INT2IP INT1IF INT1IE INT1IP TMR0IF TMR0IE TMR0IP RBIF RBIE RBIP IPEN TMR0IF TMR0IP INT1IF INT1IE INT1IP INT2IF INT2IE INT2IP RBIF RBIE RBIP INT0IF INT0IE PEIE/GIEL Interrupt to CPU Vector to Location IPEN IPEN 0018h Peripheral Interrupt Flag bit Peripheral Interrupt Enable bit Peripheral Interrupt Priority bit Peripheral Interrupt Flag bit Peripheral Interrupt Enable bit Peripheral Interrupt Priority bit TMR1IF TMR1IE TMR1IP USBIF USBIE USBIP Additional Peripheral Interrupts TMR1IF TMR1IE TMR1IP High-Priority Interrupt Generation Low-Priority Interrupt Generation USBIF USBIE USBIP Additional Peripheral Interrupts GIE/GIEH From USB Interrupt Logic From USB Interrupt Logic © 2009 Microchip Technology Inc. DS39632E-page 101 PIC18F2455/2550/4455/4550 9.2 INTCON Registers The INTCON registers are readable and writable registers which contain various enable, priority and flag bits. Note: Interrupt flag bits are set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the global interrupt enable bit. User software should ensure the appropriate interrupt flag bits are clear prior to enabling an interrupt. This feature allows for software polling. REGISTER 9-1: INTCON: INTERRUPT CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 GIE/GIEH: Global Interrupt Enable bit When IPEN = 0: 1 = Enables all unmasked interrupts 0 = Disables all interrupts When IPEN = 1: 1 = Enables all high-priority interrupts 0 = Disables all interrupts bit 6 PEIE/GIEL: Peripheral Interrupt Enable bit When IPEN = 0: 1 = Enables all unmasked peripheral interrupts 0 = Disables all peripheral interrupts When IPEN = 1: 1 = Enables all low-priority peripheral interrupts (if GIE/GIEH = 1) 0 = Disables all low-priority peripheral interrupts bit 5 TMR0IE: TMR0 Overflow Interrupt Enable bit 1 = Enables the TMR0 overflow interrupt 0 = Disables the TMR0 overflow interrupt bit 4 INT0IE: INT0 External Interrupt Enable bit 1 = Enables the INT0 external interrupt 0 = Disables the INT0 external interrupt bit 3 RBIE: RB Port Change Interrupt Enable bit 1 = Enables the RB port change interrupt 0 = Disables the RB port change interrupt bit 2 TMR0IF: TMR0 Overflow Interrupt Flag bit 1 = TMR0 register has overflowed (must be cleared in software) 0 = TMR0 register did not overflow bit 1 INT0IF: INT0 External Interrupt Flag bit 1 = The INT0 external interrupt occurred (must be cleared in software) 0 = The INT0 external interrupt did not occur bit 0 RBIF: RB Port Change Interrupt Flag bit(1) 1 = At least one of the RB7:RB4 pins changed state (must be cleared in software) 0 = None of the RB7:RB4 pins have changed state Note 1: A mismatch condition will continue to set this bit. Reading PORTB, and then waiting one additional instruction cycle, will end the mismatch condition and allow the bit to be cleared. PIC18F2455/2550/4455/4550 DS39632E-page 102 © 2009 Microchip Technology Inc. REGISTER 9-2: INTCON2: INTERRUPT CONTROL REGISTER 2 R/W-1 R/W-1 R/W-1 R/W-1 U-0 R/W-1 U-0 R/W-1 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 RBPU: PORTB Pull-up Enable bit 1 = All PORTB pull-ups are disabled 0 = PORTB pull-ups are enabled by individual port latch values bit 6 INTEDG0: External Interrupt 0 Edge Select bit 1 = Interrupt on rising edge 0 = Interrupt on falling edge bit 5 INTEDG1: External Interrupt 1 Edge Select bit 1 = Interrupt on rising edge 0 = Interrupt on falling edge bit 4 INTEDG2: External Interrupt 2 Edge Select bit 1 = Interrupt on rising edge 0 = Interrupt on falling edge bit 3 Unimplemented: Read as ‘0’ bit 2 TMR0IP: TMR0 Overflow Interrupt Priority bit 1 = High priority 0 = Low priority bit 1 Unimplemented: Read as ‘0’ bit 0 RBIP: RB Port Change Interrupt Priority bit 1 = High priority 0 = Low priority Note: Interrupt flag bits are set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the global interrupt enable bit. User software should ensure the appropriate interrupt flag bits are clear prior to enabling an interrupt. This feature allows for software polling. © 2009 Microchip Technology Inc. DS39632E-page 103 PIC18F2455/2550/4455/4550 REGISTER 9-3: INTCON3: INTERRUPT CONTROL REGISTER 3 R/W-1 R/W-1 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 INT2IP: INT2 External Interrupt Priority bit 1 = High priority 0 = Low priority bit 6 INT1IP: INT1 External Interrupt Priority bit 1 = High priority 0 = Low priority bit 5 Unimplemented: Read as ‘0’ bit 4 INT2IE: INT2 External Interrupt Enable bit 1 = Enables the INT2 external interrupt 0 = Disables the INT2 external interrupt bit 3 INT1IE: INT1 External Interrupt Enable bit 1 = Enables the INT1 external interrupt 0 = Disables the INT1 external interrupt bit 2 Unimplemented: Read as ‘0’ bit 1 INT2IF: INT2 External Interrupt Flag bit 1 = The INT2 external interrupt occurred (must be cleared in software) 0 = The INT2 external interrupt did not occur bit 0 INT1IF: INT1 External Interrupt Flag bit 1 = The INT1 external interrupt occurred (must be cleared in software) 0 = The INT1 external interrupt did not occur Note: Interrupt flag bits are set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the global interrupt enable bit. User software should ensure the appropriate interrupt flag bits are clear prior to enabling an interrupt. This feature allows for software polling. PIC18F2455/2550/4455/4550 DS39632E-page 104 © 2009 Microchip Technology Inc. 9.3 PIR Registers The PIR registers contain the individual flag bits for the peripheral interrupts. Due to the number of peripheral interrupt sources, there are two Peripheral Interrupt Request (Flag) registers (PIR1 and PIR2). Note 1: Interrupt flag bits are set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the Global Interrupt Enable bit, GIE (INTCON<7>). 2: User software should ensure the appropriate interrupt flag bits are cleared prior to enabling an interrupt and after servicing that interrupt. REGISTER 9-4: PIR1: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 1 R/W-0 R/W-0 R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SPPIF: Streaming Parallel Port Read/Write Interrupt Flag bit(1) 1 = A read or a write operation has taken place (must be cleared in software) 0 = No read or write has occurred bit 6 ADIF: A/D Converter Interrupt Flag bit 1 = An A/D conversion completed (must be cleared in software) 0 = The A/D conversion is not complete bit 5 RCIF: EUSART Receive Interrupt Flag bit 1 = The EUSART receive buffer, RCREG, is full (cleared when RCREG is read) 0 = The EUSART receive buffer is empty bit 4 TXIF: EUSART Transmit Interrupt Flag bit 1 = The EUSART transmit buffer, TXREG, is empty (cleared when TXREG is written) 0 = The EUSART transmit buffer is full bit 3 SSPIF: Master Synchronous Serial Port Interrupt Flag bit 1 = The transmission/reception is complete (must be cleared in software) 0 = Waiting to transmit/receive bit 2 CCP1IF: CCP1 Interrupt Flag bit Capture mode: 1 = A TMR1 register capture occurred (must be cleared in software) 0 = No TMR1 register capture occurred Compare mode: 1 = A TMR1 register compare match occurred (must be cleared in software) 0 = No TMR1 register compare match occurred PWM mode: Unused in this mode. bit 1 TMR2IF: TMR2 to PR2 Match Interrupt Flag bit 1 = TMR2 to PR2 match occurred (must be cleared in software) 0 = No TMR2 to PR2 match occurred bit 0 TMR1IF: TMR1 Overflow Interrupt Flag bit 1 = TMR1 register overflowed (must be cleared in software) 0 = TMR1 register did not overflow Note 1: This bit is reserved on 28-pin devices; always maintain this bit clear. © 2009 Microchip Technology Inc. DS39632E-page 105 PIC18F2455/2550/4455/4550 REGISTER 9-5: PIR2: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 2 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 OSCFIF: Oscillator Fail Interrupt Flag bit 1 = System oscillator failed, clock input has changed to INTOSC (must be cleared in software) 0 = System clock operating bit 6 CMIF: Comparator Interrupt Flag bit 1 = Comparator input has changed (must be cleared in software) 0 = Comparator input has not changed bit 5 USBIF: USB Interrupt Flag bit 1 = USB has requested an interrupt (must be cleared in software) 0 = No USB interrupt request bit 4 EEIF: Data EEPROM/Flash Write Operation Interrupt Flag bit 1 = The write operation is complete (must be cleared in software) 0 = The write operation is not complete or has not been started bit 3 BCLIF: Bus Collision Interrupt Flag bit 1 = A bus collision has occurred (must be cleared in software) 0 = No bus collision occurred bit 2 HLVDIF: High/Low-Voltage Detect Interrupt Flag bit 1 = A high/low-voltage condition occurred (must be cleared in software) 0 = No high/low-voltage event has occurred bit 1 TMR3IF: TMR3 Overflow Interrupt Flag bit 1 = TMR3 register overflowed (must be cleared in software) 0 = TMR3 register did not overflow bit 0 CCP2IF: CCP2 Interrupt Flag bit Capture mode: 1 = A TMR1 or TMR3 register capture occurred (must be cleared in software) 0 = No TMR1 or TMR3 register capture occurred Compare mode: 1 = A TMR1 or TMR3 register compare match occurred (must be cleared in software) 0 = No TMR1 or TMR3 register compare match occurred PWM mode: Unused in this mode. PIC18F2455/2550/4455/4550 DS39632E-page 106 © 2009 Microchip Technology Inc. 9.4 PIE Registers The PIE registers contain the individual enable bits for the peripheral interrupts. Due to the number of peripheral interrupt sources, there are two Peripheral Interrupt Enable registers (PIE1 and PIE2). When IPEN = 0, the PEIE bit must be set to enable any of these peripheral interrupts. REGISTER 9-6: PIE1: PERIPHERAL INTERRUPT ENABLE REGISTER 1 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SPPIE: Streaming Parallel Port Read/Write Interrupt Enable bit(1) 1 = Enables the SPP read/write interrupt 0 = Disables the SPP read/write interrupt bit 6 ADIE: A/D Converter Interrupt Enable bit 1 = Enables the A/D interrupt 0 = Disables the A/D interrupt bit 5 RCIE: EUSART Receive Interrupt Enable bit 1 = Enables the EUSART receive interrupt 0 = Disables the EUSART receive interrupt bit 4 TXIE: EUSART Transmit Interrupt Enable bit 1 = Enables the EUSART transmit interrupt 0 = Disables the EUSART transmit interrupt bit 3 SSPIE: Master Synchronous Serial Port Interrupt Enable bit 1 = Enables the MSSP interrupt 0 = Disables the MSSP interrupt bit 2 CCP1IE: CCP1 Interrupt Enable bit 1 = Enables the CCP1 interrupt 0 = Disables the CCP1 interrupt bit 1 TMR2IE: TMR2 to PR2 Match Interrupt Enable bit 1 = Enables the TMR2 to PR2 match interrupt 0 = Disables the TMR2 to PR2 match interrupt bit 0 TMR1IE: TMR1 Overflow Interrupt Enable bit 1 = Enables the TMR1 overflow interrupt 0 = Disables the TMR1 overflow interrupt Note 1: This bit is reserved on 28-pin devices; always maintain this bit clear. © 2009 Microchip Technology Inc. DS39632E-page 107 PIC18F2455/2550/4455/4550 REGISTER 9-7: PIE2: PERIPHERAL INTERRUPT ENABLE REGISTER 2 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 OSCFIE: Oscillator Fail Interrupt Enable bit 1 = Enabled 0 = Disabled bit 6 CMIE: Comparator Interrupt Enable bit 1 = Enabled 0 = Disabled bit 5 USBIE: USB Interrupt Enable bit 1 = Enabled 0 = Disabled bit 4 EEIE: Data EEPROM/Flash Write Operation Interrupt Enable bit 1 = Enabled 0 = Disabled bit 3 BCLIE: Bus Collision Interrupt Enable bit 1 = Enabled 0 = Disabled bit 2 HLVDIE: High/Low-Voltage Detect Interrupt Enable bit 1 = Enabled 0 = Disabled bit 1 TMR3IE: TMR3 Overflow Interrupt Enable bit 1 = Enabled 0 = Disabled bit 0 CCP2IE: CCP2 Interrupt Enable bit 1 = Enabled 0 = Disabled PIC18F2455/2550/4455/4550 DS39632E-page 108 © 2009 Microchip Technology Inc. 9.5 IPR Registers The IPR registers contain the individual priority bits for the peripheral interrupts. Due to the number of peripheral interrupt sources, there are two Peripheral Interrupt Priority registers (IPR1 and IPR2). Using the priority bits requires that the Interrupt Priority Enable (IPEN) bit be set. REGISTER 9-8: IPR1: PERIPHERAL INTERRUPT PRIORITY REGISTER 1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SPPIP: Streaming Parallel Port Read/Write Interrupt Priority bit(1) 1 = High priority 0 = Low priority bit 6 ADIP: A/D Converter Interrupt Priority bit 1 = High priority 0 = Low priority bit 5 RCIP: EUSART Receive Interrupt Priority bit 1 = High priority 0 = Low priority bit 4 TXIP: EUSART Transmit Interrupt Priority bit 1 = High priority 0 = Low priority bit 3 SSPIP: Master Synchronous Serial Port Interrupt Priority bit 1 = High priority 0 = Low priority bit 2 CCP1IP: CCP1 Interrupt Priority bit 1 = High priority 0 = Low priority bit 1 TMR2IP: TMR2 to PR2 Match Interrupt Priority bit 1 = High priority 0 = Low priority bit 0 TMR1IP: TMR1 Overflow Interrupt Priority bit 1 = High priority 0 = Low priority Note 1: This bit is reserved on 28-pin devices; always maintain this bit clear. © 2009 Microchip Technology Inc. DS39632E-page 109 PIC18F2455/2550/4455/4550 REGISTER 9-9: IPR2: PERIPHERAL INTERRUPT PRIORITY REGISTER 2 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 OSCFIP: Oscillator Fail Interrupt Priority bit 1 = High priority 0 = Low priority bit 6 CMIP: Comparator Interrupt Priority bit 1 = High priority 0 = Low priority bit 5 USBIP: USB Interrupt Priority bit 1 = High priority 0 = Low priority bit 4 EEIP: Data EEPROM/Flash Write Operation Interrupt Priority bit 1 = High priority 0 = Low priority bit 3 BCLIP: Bus Collision Interrupt Priority bit 1 = High priority 0 = Low priority bit 2 HLVDIP: High/Low-Voltage Detect Interrupt Priority bit 1 = High priority 0 = Low priority bit 1 TMR3IP: TMR3 Overflow Interrupt Priority bit 1 = High priority 0 = Low priority bit 0 CCP2IP: CCP2 Interrupt Priority bit 1 = High priority 0 = Low priority PIC18F2455/2550/4455/4550 DS39632E-page 110 © 2009 Microchip Technology Inc. 9.6 RCON Register The RCON register contains flag bits which are used to determine the cause of the last Reset or wake-up from Idle or Sleep modes. RCON also contains the IPEN bit which enables interrupt priorities. REGISTER 9-10: RCON: RESET CONTROL REGISTER R/W-0 R/W-1(1) U-0 R/W-1 R-1 R-1 R/W-0(2) R/W-0 IPEN SBOREN — RI TO PD POR BOR bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 IPEN: Interrupt Priority Enable bit 1 = Enable priority levels on interrupts 0 = Disable priority levels on interrupts (PIC16CXXX Compatibility mode) bit 6 SBOREN: BOR Software Enable bit(1) For details of bit operation, see Register 4-1. bit 5 Unimplemented: Read as ‘0’ bit 4 RI: RESET Instruction Flag bit For details of bit operation, see Register 4-1. bit 3 TO: Watchdog Time-out Flag bit For details of bit operation, see Register 4-1. bit 2 PD: Power-Down Detection Flag bit For details of bit operation, see Register 4-1. bit 1 POR: Power-on Reset Status bit(2) For details of bit operation, see Register 4-1. bit 0 BOR: Brown-out Reset Status bit For details of bit operation, see Register 4-1. Note 1: If SBOREN is enabled, its Reset state is ‘1’; otherwise, it is ‘0’. See Register 4-1 for additional information. 2: The actual Reset value of POR is determined by the type of device Reset. See Register 4-1 for additional information. © 2009 Microchip Technology Inc. DS39632E-page 111 PIC18F2455/2550/4455/4550 9.7 INTx Pin Interrupts External interrupts on the RB0/AN12/INT0/FLT0/SDI/ SDA, RB1/AN10/INT1/SCK/SCL and RB2/AN8/INT2/ VMO pins are edge-triggered. If the corresponding INTEDGx bit in the INTCON2 register is set (= 1), the interrupt is triggered by a rising edge; if the bit is clear, the trigger is on the falling edge. When a valid edge appears on the RBx/INTx pin, the corresponding flag bit, INTxIF, is set. This interrupt can be disabled by clearing the corresponding enable bit, INTxIE. Flag bit, INTxIF, must be cleared in software in the Interrupt Service Routine before re-enabling the interrupt. All external interrupts (INT0, INT1 and INT2) can wakeup the processor from the power-managed modes if bit, INTxIE, was set prior to going into the power-managed modes. If the Global Interrupt Enable bit, GIE, is set, the processor will branch to the interrupt vector following wake-up. Interrupt priority for INT1 and INT2 is determined by the value contained in the interrupt priority bits, INT1IP (INTCON3<6>) and INT2IP (INTCON3<7>). There is no priority bit associated with INT0. It is always a high-priority interrupt source. 9.8 TMR0 Interrupt In 8-bit mode (which is the default), an overflow in the TMR0 register (FFh → 00h) will set flag bit, TMR0IF. In 16-bit mode, an overflow in the TMR0H:TMR0L register pair (FFFFh → 0000h) will set TMR0IF. The interrupt can be enabled/disabled by setting/clearing enable bit, TMR0IE (INTCON<5>). Interrupt priority for Timer0 is determined by the value contained in the interrupt priority bit, TMR0IP (INTCON2<2>). See Section 11.0 “Timer0 Module” for further details on the Timer0 module. 9.9 PORTB Interrupt-on-Change An input change on PORTB<7:4> sets flag bit, RBIF (INTCON<0>). The interrupt can be enabled/disabled by setting/clearing enable bit, RBIE (INTCON<3>). Interrupt priority for PORTB interrupt-on-change is determined by the value contained in the interrupt priority bit, RBIP (INTCON2<0>). 9.10 Context Saving During Interrupts During interrupts, the return PC address is saved on the stack. Additionally, the WREG, STATUS and BSR registers are saved on the Fast Return Stack. If a fast return from interrupt is not used (see Section 5.3 “Data Memory Organization”), the user may need to save the WREG, STATUS and BSR registers on entry to the Interrupt Service Routine. Depending on the user’s application, other registers may also need to be saved. Example 9-1 saves and restores the WREG, STATUS and BSR registers during an Interrupt Service Routine. EXAMPLE 9-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM MOVWF W_TEMP ; W_TEMP is in virtual bank MOVFF STATUS, STATUS_TEMP ; STATUS_TEMP located anywhere MOVFF BSR, BSR_TEMP ; BSR_TMEP located anywhere ; ; USER ISR CODE ; MOVFF BSR_TEMP, BSR ; Restore BSR MOVF W_TEMP, W ; Restore WREG MOVFF STATUS_TEMP, STATUS ; Restore STATUS PIC18F2455/2550/4455/4550 DS39632E-page 112 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 113 PIC18F2455/2550/4455/4550 10.0 I/O PORTS Depending on the device selected and features enabled, there are up to five ports available. Some pins of the I/O ports are multiplexed with an alternate function from the peripheral features on the device. In general, when a peripheral is enabled, that pin may not be used as a general purpose I/O pin. Each port has three registers for its operation. These registers are: • TRIS register (data direction register) • PORT register (reads the levels on the pins of the device) • LAT register (output latch) The Data Latch register (LATA) is useful for readmodify- write operations on the value driven by the I/O pins. A simplified model of a generic I/O port, without the interfaces to other peripherals, is shown in Figure 10-1. FIGURE 10-1: GENERIC I/O PORT OPERATION 10.1 PORTA, TRISA and LATA Registers PORTA is an 8-bit wide, bidirectional port. The corresponding Data Direction register is TRISA. Setting a TRISA bit (= 1) will make the corresponding PORTA pin an input (i.e., put the corresponding output driver in a high-impedance mode). Clearing a TRISA bit (= 0) will make the corresponding PORTA pin an output (i.e., put the contents of the output latch on the selected pin). Reading the PORTA register reads the status of the pins; writing to it will write to the port latch. The Data Latch register (LATA) is also memory mapped. Read-modify-write operations on the LATA register read and write the latched output value for PORTA. The RA4 pin is multiplexed with the Timer0 module clock input to become the RA4/T0CKI pin. The RA6 pin is multiplexed with the main oscillator pin; it is enabled as an oscillator or I/O pin by the selection of the main oscillator in Configuration Register 1H (see Section 25.1 “Configuration Bits” for details). When not used as a port pin, RA6 and its associated TRIS and LAT bits are read as ‘0’. RA4 is also multiplexed with the USB module; it serves as a receiver input from an external USB transceiver. For details on configuration of the USB module, see Section 17.2 “USB Status and Control”. Several PORTA pins are multiplexed with analog inputs, the analog VREF+ and VREF- inputs and the comparator voltage reference output. The operation of pins RA5 and RA3:RA0 as A/D converter inputs is selected by clearing/setting the control bits in the ADCON1 register (A/D Control Register 1). All other PORTA pins have TTL input levels and full CMOS output drivers. The TRISA register controls the direction of the RA pins, even when they are being used as analog inputs. The user must ensure the bits in the TRISA register are maintained set when using them as analog inputs. EXAMPLE 10-1: INITIALIZING PORTA Data Bus WR LAT WR TRIS RD PORT Data Latch TRIS Latch RD TRIS Input Buffer I/O pin(1) D Q CK D Q CK EN Q D EN RD LAT or PORT Note 1: I/O pins have diode protection to VDD and VSS. Note: On a Power-on Reset, RA5 and RA3:RA0 are configured as analog inputs and read as ‘0’. RA4 is configured as a digital input. CLRF PORTA ; Initialize PORTA by ; clearing output ; data latches CLRF LATA ; Alternate method ; to clear output ; data latches MOVLW 0Fh ; Configure A/D MOVWF ADCON1 ; for digital inputs MOVLW 07h ; Configure comparators MOVWF CMCON ; for digital input MOVLW 0CFh ; Value used to ; initialize data ; direction MOVWF TRISA ; Set RA<3:0> as inputs ; RA<5:4> as outputs PIC18F2455/2550/4455/4550 DS39632E-page 114 © 2009 Microchip Technology Inc. TABLE 10-1: PORTA I/O SUMMARY Pin Function TRIS Setting I/O I/O Type Description RA0/AN0 RA0 0 OUT DIG LATA<0> data output; not affected by analog input. 1 IN TTL PORTA<0> data input; disabled when analog input enabled. AN0 1 IN ANA A/D Input Channel 0 and Comparator C1- input. Default configuration on POR; does not affect digital output. RA1/AN1 RA1 0 OUT DIG LATA<1> data output; not affected by analog input. 1 IN TTL PORTA<1> data input; reads ‘0’ on POR. AN1 1 IN ANA A/D Input Channel 1 and Comparator C2- input. Default configuration on POR; does not affect digital output. RA2/AN2/ VREF-/CVREF RA2 0 OUT DIG LATA<2> data output; not affected by analog input. Disabled when CVREF output enabled. 1 IN TTL PORTA<2> data input. Disabled when analog functions enabled; disabled when CVREF output enabled. AN2 1 IN ANA A/D Input Channel 2 and Comparator C2+ input. Default configuration on POR; not affected by analog output. VREF- 1 IN ANA A/D and comparator voltage reference low input. CVREF x OUT ANA Comparator voltage reference output. Enabling this feature disables digital I/O. RA3/AN3/ VREF+ RA3 0 OUT DIG LATA<3> data output; not affected by analog input. 1 IN TTL PORTA<3> data input; disabled when analog input enabled. AN3 1 IN ANA A/D Input Channel 3 and Comparator C1+ input. Default configuration on POR. VREF+ 1 IN ANA A/D and comparator voltage reference high input. RA4/T0CKI/ C1OUT/RCV RA4 0 OUT DIG LATA<4> data output; not affected by analog input. 1 IN ST PORTA<4> data input; disabled when analog input enabled. T0CKI 1 IN ST Timer0 clock input. C1OUT 0 OUT DIG Comparator 1 output; takes priority over port data. RCV x IN TTL External USB transceiver RCV input. RA5/AN4/SS/ HLVDIN/C2OUT RA5 0 OUT DIG LATA<5> data output; not affected by analog input. 1 IN TTL PORTA<5> data input; disabled when analog input enabled. AN4 1 IN ANA A/D Input Channel 4. Default configuration on POR. SS 1 IN TTL Slave select input for MSSP module. HLVDIN 1 IN ANA High/Low-Voltage Detect external trip point input. C2OUT 0 OUT DIG Comparator 2 output; takes priority over port data. OSC2/CLKO/ RA6 OSC2 x OUT ANA Main oscillator feedback output connection (all XT and HS modes). CLKO x OUT DIG System cycle clock output (FOSC/4); available in EC, ECPLL and INTCKO modes. RA6 0 OUT DIG LATA<6> data output. Available only in ECIO, ECPIO and INTIO modes; otherwise, reads as ‘0’. 1 IN TTL PORTA<6> data input. Available only in ECIO, ECPIO and INTIO modes; otherwise, reads as ‘0’. Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input, TTL = TTL Buffer Input, x = Don’t care (TRIS bit does not affect port direction or is overridden for this option) © 2009 Microchip Technology Inc. DS39632E-page 115 PIC18F2455/2550/4455/4550 TABLE 10-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page PORTA — RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 56 LATA — LATA6(1) LATA5 LATA4 LATA3 LATA2 LATA1 LATA0 56 TRISA — TRISA6(1) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 54 CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 55 CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 55 UCON — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — 57 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTA. Note 1: RA6 and its associated latch and data direction bits are enabled as I/O pins based on oscillator configuration; otherwise, they are read as ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 116 © 2009 Microchip Technology Inc. 10.2 PORTB, TRISB and LATB Registers PORTB is an 8-bit wide, bidirectional port. The corresponding Data Direction register is TRISB. Setting a TRISB bit (= 1) will make the corresponding PORTB pin an input (i.e., put the corresponding output driver in a high-impedance mode). Clearing a TRISB bit (= 0) will make the corresponding PORTB pin an output (i.e., put the contents of the output latch on the selected pin). The Data Latch register (LATB) is also memory mapped. Read-modify-write operations on the LATB register read and write the latched output value for PORTB. Each of the PORTB pins has a weak internal pull-up. A single control bit can turn on all the pull-ups. This is performed by clearing bit, RBPU (INTCON2<7>). The weak pull-up is automatically turned off when the port pin is configured as an output. The pull-ups are disabled on a Power-on Reset. Four of the PORTB pins (RB7:RB4) have an interrupton- change feature. Only pins configured as inputs can cause this interrupt to occur. Any RB7:RB4 pin configured as an output is excluded from the interrupton- change comparison. The pins are compared with the old value latched on the last read of PORTB. The “mismatch” outputs of RB7:RB4 are ORed together to generate the RB Port Change Interrupt with Flag bit, RBIF (INTCON<0>). The interrupt-on-change can be used to wake the device from Sleep. The user, in the Interrupt Service Routine, can clear the interrupt in the following manner: a) Any read or write of PORTB (except with the MOVFF (ANY), PORTB instruction). This will end the mismatch condition. b) Wait one TCY delay (for example, execute one NOP instruction). c) Clear flag bit, RBIF A mismatch condition will continue to set flag bit, RBIF. Reading PORTB will end the mismatch condition and allow flag bit, RBIF, to be cleared after a one TCY delay. The interrupt-on-change feature is recommended for wake-up on key depression operation and operations where PORTB is only used for the interrupt-on-change feature. Polling of PORTB is not recommended while using the interrupt-on-change feature. Pins, RB2 and RB3, are multiplexed with the USB peripheral and serve as the differential signal outputs for an external USB transceiver (TRIS configuration). Refer to Section 17.2.2.2 “External Transceiver” for additional information on configuring the USB module for operation with an external transceiver. RB4 is multiplexed with CSSPP, the chip select function for the Streaming Parallel Port (SPP) – TRIS setting. Details of its operation are discussed in Section 18.0 “Streaming Parallel Port”. EXAMPLE 10-2: INITIALIZING PORTB Note: On a Power-on Reset, RB4:RB0 are configured as analog inputs by default and read as ‘0’; RB7:RB5 are configured as digital inputs. By programming the Configuration bit, PBADEN (CONFIG3H<1>), RB4:RB0 will alternatively be configured as digital inputs on POR. CLRF PORTB ; Initialize PORTB by ; clearing output ; data latches CLRF LATB ; Alternate method ; to clear output ; data latches MOVLW 0Eh ; Set RB<4:0> as MOVWF ADCON1 ; digital I/O pins ; (required if config bit ; PBADEN is set) MOVLW 0CFh ; Value used to ; initialize data ; direction MOVWF TRISB ; Set RB<3:0> as inputs ; RB<5:4> as outputs ; RB<7:6> as inputs © 2009 Microchip Technology Inc. DS39632E-page 117 PIC18F2455/2550/4455/4550 TABLE 10-3: PORTB I/O SUMMARY Pin Function TRIS Setting I/O I/O Type Description RB0/AN12/ INT0/FLT0/ SDI/SDA RB0 0 OUT DIG LATB<0> data output; not affected by analog input. 1 IN TTL PORTB<0> data input; weak pull-up when RBPU bit is cleared. Disabled when analog input enabled.(1) AN12 1 IN ANA A/D Input Channel 12.(1) INT0 1 IN ST External Interrupt 0 input. FLT0 1 IN ST Enhanced PWM Fault input (ECCP1 module); enabled in software. SDI 1 IN ST SPI data input (MSSP module). SDA 1 OUT DIG I2C™ data output (MSSP module); takes priority over port data. 1 IN I2C/SMB I2C data input (MSSP module); input type depends on module setting. RB1/AN10/ INT1/SCK/ SCL RB1 0 OUT DIG LATB<1> data output; not affected by analog input. 1 IN TTL PORTB<1> data input; weak pull-up when RBPU bit is cleared. Disabled when analog input enabled.(1) AN10 1 IN ANA A/D Input Channel 10.(1) INT1 1 IN ST External Interrupt 1 input. SCK 0 OUT DIG SPI clock output (MSSP module); takes priority over port data. 1 IN ST SPI clock input (MSSP module). SCL 0 OUT DIG I2C clock output (MSSP module); takes priority over port data. 1 IN I2C/SMB I2C clock input (MSSP module); input type depends on module setting. RB2/AN8/ INT2/VMO RB2 0 OUT DIG LATB<2> data output; not affected by analog input. 1 IN TTL PORTB<2> data input; weak pull-up when RBPU bit is cleared. Disabled when analog input enabled.(1) AN8 1 IN ANA A/D input channel 8.(1) INT2 1 IN ST External Interrupt 2 input. VMO 0 OUT DIG External USB transceiver VMO data output. RB3/AN9/ CCP2/VPO RB3 0 OUT DIG LATB<3> data output; not affected by analog input. 1 IN TTL PORTB<3> data input; weak pull-up when RBPU bit is cleared. Disabled when analog input enabled.(1) AN9 1 IN ANA A/D Input Channel 9.(1) CCP2(2) 0 OUT DIG CCP2 compare and PWM output. 1 IN ST CCP2 capture input. VPO 0 OUT DIG External USB transceiver VPO data output. RB4/AN11/ KBI0/CSSPP RB4 0 OUT DIG LATB<4> data output; not affected by analog input. 1 IN TTL PORTB<4> data input; weak pull-up when RBPU bit is cleared. Disabled when analog input enabled.(1) AN11 1 IN ANA A/D Input Channel 11.(1) KBI0 1 IN TTL Interrupt-on-pin change. CSSPP(4) 0 OUT DIG SPP chip select control output. RB5/KBI1/ PGM RB5 0 OUT DIG LATB<5> data output. 1 IN TTL PORTB<5> data input; weak pull-up when RBPU bit is cleared. KBI1 1 IN TTL Interrupt-on-pin change. PGM x IN ST Single-Supply Programming mode entry (ICSP™). Enabled by LVP Configuration bit; all other pin functions disabled. Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input, I2C/SMB = I2C/SMBus input buffer, TTL = TTL Buffer Input, x = Don’t care (TRIS bit does not affect port direction or is overridden for this option) Note 1: Configuration on POR is determined by PBADEN Configuration bit. Pins are configured as analog inputs when PBADEN is set and digital inputs when PBADEN is cleared. 2: Alternate pin assignment for CCP2 when CCP2MX = 0. Default assignment is RC1. 3: All other pin functions are disabled when ICSP™ or ICD operation is enabled. 4: 40/44-pin devices only. PIC18F2455/2550/4455/4550 DS39632E-page 118 © 2009 Microchip Technology Inc. TABLE 10-4: SUMMARY OF REGISTERS ASSOCIATED WITH PORTB RB6/KBI2/ PGC RB6 0 OUT DIG LATB<6> data output. 1 IN TTL PORTB<6> data input; weak pull-up when RBPU bit is cleared. KBI2 1 IN TTL Interrupt-on-pin change. PGC x IN ST Serial execution (ICSP™) clock input for ICSP and ICD operation.(3) RB7/KBI3/ PGD RB7 0 OUT DIG LATB<7> data output. 1 IN TTL PORTB<7> data input; weak pull-up when RBPU bit is cleared. KBI3 1 IN TTL Interrupt-on-pin change. PGD x OUT DIG Serial execution data output for ICSP and ICD operation.(3) x IN ST Serial execution data input for ICSP and ICD operation.(3) TABLE 10-3: PORTB I/O SUMMARY (CONTINUED) Pin Function TRIS Setting I/O I/O Type Description Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input, I2C/SMB = I2C/SMBus input buffer, TTL = TTL Buffer Input, x = Don’t care (TRIS bit does not affect port direction or is overridden for this option) Note 1: Configuration on POR is determined by PBADEN Configuration bit. Pins are configured as analog inputs when PBADEN is set and digital inputs when PBADEN is cleared. 2: Alternate pin assignment for CCP2 when CCP2MX = 0. Default assignment is RC1. 3: All other pin functions are disabled when ICSP™ or ICD operation is enabled. 4: 40/44-pin devices only. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 56 LATB LATB7 LATB6 LATB5 LATB4 LATB3 LATB2 LATB1 LATB0 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP 53 INTCON3 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF 53 ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 54 SPPCON(1) — — — — — — SPPOWN SPPEN 57 SPPCFG(1) CLKCFG1 CLKCFG0 CSEN CLK1EN WS3 WS2 WS1 WS0 57 UCON — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — 57 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTB. Note 1: These registers are unimplemented on 28-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 119 PIC18F2455/2550/4455/4550 10.3 PORTC, TRISC and LATC Registers PORTC is a 7-bit wide, bidirectional port. The corresponding Data Direction register is TRISC. Setting a TRISC bit (= 1) will make the corresponding PORTC pin an input (i.e., put the corresponding output driver in a high-impedance mode). Clearing a TRISC bit (= 0) will make the corresponding PORTC pin an output (i.e., put the contents of the output latch on the selected pin). The RC3 pin is not implemented in these devices. The Data Latch register (LATC) is also memory mapped. Read-modify-write operations on the LATC register read and write the latched output value for PORTC. PORTC is primarily multiplexed with serial communication modules, including the EUSART, MSSP module and the USB module (Table 10-5). Except for RC4 and RC5, PORTC uses Schmitt Trigger input buffers. Pins RC4 and RC5 are multiplexed with the USB module. Depending on the configuration of the module, they can serve as the differential data lines for the onchip USB transceiver, or the data inputs from an external USB transceiver. Both RC4 and RC5 have TTL input buffers instead of the Schmitt Trigger buffers on the other pins. Unlike other PORTC pins, RC4 and RC5 do not have TRISC bits associated with them. As digital ports, they can only function as digital inputs. When configured for USB operation, the data direction is determined by the configuration and status of the USB module at a given time. If an external transceiver is used, RC4 and RC5 always function as inputs from the transceiver. If the on-chip transceiver is used, the data direction is determined by the operation being performed by the module at that time. When the external transceiver is enabled, RC2 also serves as the output enable control to the transceiver. Additional information on configuring USB options is provided in Section 17.2.2.2 “External Transceiver”. When enabling peripheral functions on PORTC pins other than RC4 and RC5, care should be taken in defining the TRIS bits. Some peripherals override the TRIS bit to make a pin an output, while other peripherals override the TRIS bit to make a pin an input. The user should refer to the corresponding peripheral section for the correct TRIS bit settings. The contents of the TRISC register are affected by peripheral overrides. Reading TRISC always returns the current contents, even though a peripheral device may be overriding one or more of the pins. EXAMPLE 10-3: INITIALIZING PORTC Note: On a Power-on Reset, these pins, except RC4 and RC5, are configured as digital inputs. To use pins RC4 and RC5 as digital inputs, the USB module must be disabled (UCON<3> = 0) and the on-chip USB transceiver must be disabled (UCFG<3> = 1). CLRF PORTC ; Initialize PORTC by ; clearing output ; data latches CLRF LATC ; Alternate method ; to clear output ; data latches MOVLW 07h ; Value used to ; initialize data ; direction MOVWF TRISC ; RC<5:0> as outputs ; RC<7:6> as inputs PIC18F2455/2550/4455/4550 DS39632E-page 120 © 2009 Microchip Technology Inc. TABLE 10-5: PORTC I/O SUMMARY Pin Function TRIS Setting I/O I/O Type Description RC0/T1OSO/ T13CKI RC0 0 OUT DIG LATC<0> data output. 1 IN ST PORTC<0> data input. T1OSO x OUT ANA Timer1 oscillator output; enabled when Timer1 oscillator enabled. Disables digital I/O. T13CKI 1 IN ST Timer1/Timer3 counter input. RC1/T1OSI/ CCP2/UOE RC1 0 OUT DIG LATC<1> data output. 1 IN ST PORTC<1> data input. T1OSI x IN ANA Timer1 oscillator input; enabled when Timer1 oscillator enabled. Disables digital I/O. CCP2(1) 0 OUT DIG CCP2 compare and PWM output; takes priority over port data. 1 IN ST CCP2 capture input. UOE 0 OUT DIG External USB transceiver OE output. RC2/CCP1/ P1A RC2 0 OUT DIG LATC<2> data output. 1 IN ST PORTC<2> data input. CCP1 0 OUT DIG ECCP1 compare and PWM output; takes priority over port data. 1 IN ST ECCP1 capture input. P1A(3) 0 OUT DIG ECCP1 Enhanced PWM output, Channel A; takes priority over port data. May be configured for tri-state during Enhanced PWM shutdown events. RC4/D-/VM RC4 —(2) IN TTL PORTC<4> data input; disabled when USB module or on-chip transceiver are enabled. D- —(2) OUT XCVR USB bus differential minus line output (internal transceiver). —(2) IN XCVR USB bus differential minus line input (internal transceiver). VM —(2) IN TTL External USB transceiver VM input. RC5/D+/VP RC5 —(2) IN TTL PORTC<5> data input; disabled when USB module or on-chip transceiver are enabled. D+ —(2) OUT XCVR USB bus differential plus line output (internal transceiver). —(2) IN XCVR USB bus differential plus line input (internal transceiver). VP —(2) IN TTL External USB transceiver VP input. RC6/TX/CK RC6 0 OUT DIG LATC<6> data output. 1 IN ST PORTC<6> data input. TX 0 OUT DIG Asynchronous serial transmit data output (EUSART module); takes priority over port data. User must configure as output. CK 0 OUT DIG Synchronous serial clock output (EUSART module); takes priority over port data. 1 IN ST Synchronous serial clock input (EUSART module). Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input, TTL = TTL Buffer Input, XCVR = USB transceiver, x = Don’t care (TRIS bit does not affect port direction or is overridden for this option) Note 1: Default pin assignment. Alternate pin assignment is RB3 (when CCP2MX = 0). 2: RC4 and RC5 do not have corresponding TRISC bits. In Port mode, these pins are input only. USB data direction is determined by the USB configuration. 3: 40/44-pin devices only. © 2009 Microchip Technology Inc. DS39632E-page 121 PIC18F2455/2550/4455/4550 TABLE 10-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC RC7/RX/DT/ SDO RC7 0 OUT DIG LATC<7> data output. 1 IN ST PORTC<7> data input. RX 1 IN ST Asynchronous serial receive data input (EUSART module). DT 1 OUT DIG Synchronous serial data output (EUSART module); takes priority over SPI and port data. 1 IN ST Synchronous serial data input (EUSART module). User must configure as an input. SDO 0 OUT DIG SPI data output (MSSP module); takes priority over port data. TABLE 10-5: PORTC I/O SUMMARY (CONTINUED) Pin Function TRIS Setting I/O I/O Type Description Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input, TTL = TTL Buffer Input, XCVR = USB transceiver, x = Don’t care (TRIS bit does not affect port direction or is overridden for this option) Note 1: Default pin assignment. Alternate pin assignment is RB3 (when CCP2MX = 0). 2: RC4 and RC5 do not have corresponding TRISC bits. In Port mode, these pins are input only. USB data direction is determined by the USB configuration. 3: 40/44-pin devices only. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page PORTC RC7 RC6 RC5(1) RC4(1) — RC2 RC1 RC0 56 LATC LATC7 LATC6 — — — LATC2 LATC1 LATC0 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 UCON — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — 57 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTC. Note 1: RC5 and RC4 are only available as port pins when the USB module is disabled (UCON<3> = 0). PIC18F2455/2550/4455/4550 DS39632E-page 122 © 2009 Microchip Technology Inc. 10.4 PORTD, TRISD and LATD Registers PORTD is an 8-bit wide, bidirectional port. The corresponding Data Direction register is TRISD. Setting a TRISD bit (= 1) will make the corresponding PORTD pin an input (i.e., put the corresponding output driver in a high-impedance mode). Clearing a TRISD bit (= 0) will make the corresponding PORTD pin an output (i.e., put the contents of the output latch on the selected pin). The Data Latch register (LATD) is also memory mapped. Read-modify-write operations on the LATD register read and write the latched output value for PORTD. All pins on PORTD are implemented with Schmitt Trigger input buffers. Each pin is individually configurable as an input or output. Each of the PORTD pins has a weak internal pull-up. A single control bit, RDPU (PORTE<7>), can turn on all the pull-ups. This is performed by setting RDPU. The weak pull-up is automatically turned off when the port pin is configured as a digital output or as one of the other multiplexed peripherals. The pull-ups are disabled on a Power-on Reset. The PORTE register is shown in Section 10.5 “PORTE, TRISE and LATE Registers”. Three of the PORTD pins are multiplexed with outputs, P1B, P1C and P1D, of the Enhanced CCP module. The operation of these additional PWM output pins is covered in greater detail in Section 16.0 “Enhanced Capture/Compare/PWM (ECCP) Module”. PORTD can also be configured as an 8-bit wide Streaming Parallel Port (SPP). In this mode, the input buffers are TTL. For additional information on configuration and uses of the SPP, see Section 18.0 “Streaming Parallel Port”. EXAMPLE 10-4: INITIALIZING PORTD Note: PORTD is only available on 40/44-pin devices. Note: On a Power-on Reset, these pins are configured as digital inputs. Note: When the Enhanced PWM mode is used with either dual or quad outputs, the MSSP functions of PORTD are automatically disabled. CLRF PORTD ; Initialize PORTD by ; clearing output ; data latches CLRF LATD ; Alternate method ; to clear output ; data latches MOVLW 0CFh ; Value used to ; initialize data ; direction MOVWF TRISD ; Set RD<3:0> as inputs ; RD<5:4> as outputs ; RD<7:6> as inputs © 2009 Microchip Technology Inc. DS39632E-page 123 PIC18F2455/2550/4455/4550 TABLE 10-7: PORTD I/O SUMMARY Pin Function TRIS Setting I/O I/O Type Description RD0/SPP0 RD0 0 OUT DIG LATD<0> data output. 1 IN ST PORTD<0> data input. SPP0 1 OUT DIG SPP<0> output data; takes priority over port data. 1 IN TTL SPP<0> input data. RD1/SPP1 RD1 0 OUT DIG LATD<1> data output. 1 IN ST PORTD<1> data input. SPP1 1 OUT DIG SPP<1> output data; takes priority over port data. 1 IN TTL SPP<1> input data. RD2/SPP2 RD2 0 OUT DIG LATD<2> data output. 1 IN ST PORTD<2> data input. SPP2 1 OUT DIG SPP<2> output data; takes priority over port data. 1 IN TTL SPP<2> input data. RD3/SPP3 RD3 0 OUT DIG LATD<3> data output. 1 IN ST PORTD<3> data input. SPP3 1 OUT DIG SPP<3> output data; takes priority over port data. 1 IN TTL SPP<3> input data. RD4/SPP4 RD4 0 OUT DIG LATD<4> data output. 1 IN ST PORTD<4> data input. SPP4 1 OUT DIG SPP<4> output data; takes priority over port data. 1 IN TTL SPP<4> input data. RD5/SPP5/P1B RD5 0 OUT DIG LATD<5> data output 1 IN ST PORTD<5> data input SPP5 1 OUT DIG SPP<5> output data; takes priority over port data. 1 IN TTL SPP<5> input data. P1B 0 OUT DIG ECCP1 Enhanced PWM output, Channel B; takes priority over port and SPP data.(1) RD6/SPP6/P1C RD6 0 OUT DIG LATD<6> data output. 1 IN ST PORTD<6> data input. SPP6 1 OUT DIG SPP<6> output data; takes priority over port data. 1 IN TTL SPP<6> input data. P1C 0 OUT DIG ECCP1 Enhanced PWM output, Channel C; takes priority over port and SPP data.(1) RD7/SPP7/P1D RD7 0 OUT DIG LATD<7> data output. 1 IN ST PORTD<7> data input. SPP7 1 OUT DIG SPP<7> output data; takes priority over port data. 1 IN TTL SPP<7> input data. P1D 0 OUT DIG ECCP1 Enhanced PWM output, Channel D; takes priority over port and SPP data.(1) Legend: OUT = Output, IN = Input, DIG = Digital Output, ST = Schmitt Buffer Input, TTL = TTL Buffer Input Note 1: May be configured for tri-state during Enhanced PWM shutdown events. PIC18F2455/2550/4455/4550 DS39632E-page 124 © 2009 Microchip Technology Inc. TABLE 10-8: SUMMARY OF REGISTERS ASSOCIATED WITH PORTD Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page PORTD(3) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 56 LATD(3) LATD7 LATD6 LATD5 LATD4 LATD3 LATD2 LATD1 LATD0 56 TRISD(3) TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 56 PORTE RDPU(3) — — — RE3(1,2) RE2(3) RE1(3) RE0(3) 56 CCP1CON P1M1(3) P1M0(3) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 55 SPPCON(3) — — — — — — SPPOWN SPPEN 57 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTD. Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0). 2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are implemented only when PORTE is implemented (i.e., 40/44-pin devices). 3: These registers and/or bits are unimplemented on 28-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 125 PIC18F2455/2550/4455/4550 10.5 PORTE, TRISE and LATE Registers Depending on the particular PIC18F2455/2550/4455/ 4550 device selected, PORTE is implemented in two different ways. For 40/44-pin devices, PORTE is a 4-bit wide port. Three pins (RE0/AN5/CK1SPP, RE1/AN6/CK2SPP and RE2/AN7/OESPP) are individually configurable as inputs or outputs. These pins have Schmitt Trigger input buffers. When selected as an analog input, these pins will read as ‘0’s. The corresponding Data Direction register is TRISE. Setting a TRISE bit (= 1) will make the corresponding PORTE pin an input (i.e., put the corresponding output driver in a high-impedance mode). Clearing a TRISE bit (= 0) will make the corresponding PORTE pin an output (i.e., put the contents of the output latch on the selected pin). In addition to port data, the PORTE register (Register 10-1) also contains the RDPU control bit (PORTE<7>); this enables or disables the weak pull-ups on PORTD. TRISE controls the direction of the RE pins, even when they are being used as analog inputs. The user must make sure to keep the pins configured as inputs when using them as analog inputs. The Data Latch register (LATE) is also memory mapped. Read-modify-write operations on the LATE register read and write the latched output value for PORTE. The fourth pin of PORTE (MCLR/VPP/RE3) is an input only pin. Its operation is controlled by the MCLRE Configuration bit. When selected as a port pin (MCLRE = 0), it functions as a digital input only pin; as such, it does not have TRIS or LAT bits associated with its operation. Otherwise, it functions as the device’s Master Clear input. In either configuration, RE3 also functions as the programming voltage input during programming. EXAMPLE 10-5: INITIALIZING PORTE 10.5.1 PORTE IN 28-PIN DEVICES For 28-pin devices, PORTE is only available when Master Clear functionality is disabled (MCLRE = 0). In these cases, PORTE is a single bit, input only port comprised of RE3 only. The pin operates as previously described. Note: On a Power-on Reset, RE2:RE0 are configured as analog inputs. Note: On a Power-on Reset, RE3 is enabled as a digital input only if Master Clear functionality is disabled. CLRF PORTE ; Initialize PORTE by ; clearing output ; data latches CLRF LATE ; Alternate method ; to clear output ; data latches MOVLW 0Ah ; Configure A/D MOVWF ADCON1 ; for digital inputs MOVLW 03h ; Value used to ; initialize data ; direction MOVLW 07h ; Turn off MOVWF CMCON ; comparators MOVWF TRISC ; Set RE<0> as inputs ; RE<1> as outputs ; RE<2> as inputs REGISTER 10-1: PORTE REGISTER R/W-0 U-0 U-0 U-0 R/W-x R/W-0 R/W-0 R/W-0 RDPU(3) — — — RE3(1,2) RE2(3) RE1(3) RE0(3) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 RDPU: PORTD Pull-up Enable bit 1 = PORTD pull-ups are enabled by individual port latch values 0 = All PORTD pull-ups are disabled bit 6-4 Unimplemented: Read as ‘0’ bit 3-0 RE3:RE0: PORTE Data Input bits(1,2,3) Note 1: implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0); otherwise, read as ‘0’. 2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are implemented only when PORTE is implemented (i.e., 40/44-pin devices). 3: Unimplemented in 28-pin devices; read as ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 126 © 2009 Microchip Technology Inc. TABLE 10-9: PORTE I/O SUMMARY TABLE 10-10: SUMMARY OF REGISTERS ASSOCIATED WITH PORTE Pin Function TRIS Setting I/O I/O Type Description RE0/AN5/ CK1SPP RE0 0 OUT DIG LATE<0> data output; not affected by analog input. 1 IN ST PORTE<0> data input; disabled when analog input enabled. AN5 1 IN ANA A/D Input Channel 5; default configuration on POR. CK1SPP 0 OUT DIG SPP clock 1 output (SPP enabled). RE1/AN6/ CK2SPP RE1 0 OUT DIG LATE<1> data output; not affected by analog input. 1 IN ST PORTE<1> data input; disabled when analog input enabled. AN6 1 IN ANA A/D Input Channel 6; default configuration on POR. CK2SPP 0 OUT DIG SPP clock 2 output (SPP enabled). RE2/AN7/ OESPP RE2 0 OUT DIG LATE<2> data output; not affected by analog input. 1 IN ST PORTE<2> data input; disabled when analog input enabled. AN7 1 IN ANA A/D Input Channel 7; default configuration on POR. OESPP 0 OUT DIG SPP enable output (SPP enabled). MCLR/VPP/ RE3 MCLR —(1) IN ST External Master Clear input; enabled when MCLRE Configuration bit is set. VPP — (1) IN ANA High-voltage detection, used for ICSP™ mode entry detection. Always available regardless of pin mode. RE3 — (1) IN ST PORTE<3> data input; enabled when MCLRE Configuration bit is clear. Legend: OUT = Output, IN = Input, ANA = Analog Signal, DIG = Digital Output, ST = Schmitt Buffer Input Note 1: RE3 does not have a corresponding TRISE<3> bit. This pin is always an input regardless of mode. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page PORTE RDPU(3) — — — RE3(1,2) RE2(3) RE1(3) RE0(3) 56 LATE(3) — — — — — LATE2 LATE1 LATE0 56 TRISE(3) — — — — — TRISE2 TRISE1 TRISE0 56 ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 54 CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 55 SPPCON(3) — — — — — — SPPOWN SPPEN 57 SPPCFG(3) CLKCFG1 CLKCFG0 CSEN CLK1EN WS3 WS2 WS1 WS0 57 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTE. Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0). 2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are implemented only when PORTE is implemented (i.e., 40/44-pin devices). 3: These registers or bits are unimplemented on 28-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 127 PIC18F2455/2550/4455/4550 11.0 TIMER0 MODULE The Timer0 module incorporates the following features: • Software selectable operation as a timer or counter in both 8-bit or 16-bit modes • Readable and writable registers • Dedicated 8-bit, software programmable prescaler • Selectable clock source (internal or external) • Edge select for external clock • Interrupt on overflow The T0CON register (Register 11-1) controls all aspects of the module’s operation, including the prescale selection. It is both readable and writable. A simplified block diagram of the Timer0 module in 8-bit mode is shown in Figure 11-1. Figure 11-2 shows a simplified block diagram of the Timer0 module in 16-bit mode. REGISTER 11-1: T0CON: TIMER0 CONTROL REGISTER R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 TMR0ON: Timer0 On/Off Control bit 1 = Enables Timer0 0 = Stops Timer0 bit 6 T08BIT: Timer0 8-Bit/16-Bit Control bit 1 = Timer0 is configured as an 8-bit timer/counter 0 = Timer0 is configured as a 16-bit timer/counter bit 5 T0CS: Timer0 Clock Source Select bit 1 = Transition on T0CKI pin 0 = Internal instruction cycle clock (CLKO) bit 4 T0SE: Timer0 Source Edge Select bit 1 = Increment on high-to-low transition on T0CKI pin 0 = Increment on low-to-high transition on T0CKI pin bit 3 PSA: Timer0 Prescaler Assignment bit 1 = TImer0 prescaler is NOT assigned. Timer0 clock input bypasses prescaler. 0 = Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output. bit 2-0 T0PS2:T0PS0: Timer0 Prescaler Select bits 111 = 1:256 Prescale value 110 = 1:128 Prescale value 101 = 1:64 Prescale value 100 = 1:32 Prescale value 011 = 1:16 Prescale value 010 = 1:8 Prescale value 001 = 1:4 Prescale value 000 = 1:2 Prescale value PIC18F2455/2550/4455/4550 DS39632E-page 128 © 2009 Microchip Technology Inc. 11.1 Timer0 Operation Timer0 can operate as either a timer or a counter; the mode is selected by clearing the T0CS bit (T0CON<5>). In Timer mode, the module increments on every clock by default unless a different prescaler value is selected (see Section 11.3 “Prescaler”). If the TMR0 register is written to, the increment is inhibited for the following two instruction cycles. The user can work around this by writing an adjusted value to the TMR0 register. The Counter mode is selected by setting the T0CS bit (= 1). In Counter mode, Timer0 increments either on every rising or falling edge of pin RA4/T0CKI/C1OUT/ RCV. The incrementing edge is determined by the Timer0 Source Edge Select bit, T0SE (T0CON<4>); clearing this bit selects the rising edge. Restrictions on the external clock input are discussed below. An external clock source can be used to drive Timer0; however, it must meet certain requirements to ensure that the external clock can be synchronized with the internal phase clock (TOSC). There is a delay between synchronization and the onset of incrementing the timer/counter. 11.2 Timer0 Reads and Writes in 16-Bit Mode TMR0H is not the actual high byte of Timer0 in 16-bit mode. It is actually a buffered version of the real high byte of Timer0 which is not directly readable nor writable (refer to Figure 11-2). TMR0H is updated with the contents of the high byte of Timer0 during a read of TMR0L. This provides the ability to read all 16 bits of Timer0 without having to verify that the read of the high and low byte were valid, due to a rollover between successive reads of the high and low byte. Similarly, a write to the high byte of Timer0 must also take place through the TMR0H Buffer register. The high byte is updated with the contents of TMR0H when a write occurs to TMR0L. This allows all 16 bits of Timer0 to be updated at once. FIGURE 11-1: TIMER0 BLOCK DIAGRAM (8-BIT MODE) FIGURE 11-2: TIMER0 BLOCK DIAGRAM (16-BIT MODE) Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI maximum prescale. T0CKI pin T0SE 0 1 1 0 T0CS FOSC/4 Programmable Prescaler Sync with Internal Clocks TMR0L (2 TCY Delay) PSA Internal Data Bus T0PS2:T0PS0 Set TMR0IF on Overflow 3 8 8 Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI maximum prescale. T0CKI pin T0SE 0 1 1 0 T0CS FOSC/4 Programmable Prescaler Sync with Internal Clocks TMR0L (2 TCY Delay) Internal Data Bus 8 PSA T0PS2:T0PS0 Set TMR0IF on Overflow 3 TMR0 TMR0H High Byte 8 8 8 Read TMR0L Write TMR0L 8 © 2009 Microchip Technology Inc. DS39632E-page 129 PIC18F2455/2550/4455/4550 11.3 Prescaler An 8-bit counter is available as a prescaler for the Timer0 module. The prescaler is not directly readable or writable; its value is set by the PSA and T0PS2:T0PS0 bits (T0CON<3:0>) which determine the prescaler assignment and prescale ratio. Clearing the PSA bit assigns the prescaler to the Timer0 module. When it is assigned, prescale values from 1:2 through 1:256, in power-of-2 increments, are selectable. When assigned to the Timer0 module, all instructions writing to the TMR0 register (e.g., CLRF TMR0, MOVWF TMR0, BSF TMR0,etc.) clear the prescaler count. 11.3.1 SWITCHING PRESCALER ASSIGNMENT The prescaler assignment is fully under software control and can be changed “on-the-fly” during program execution. 11.4 Timer0 Interrupt The TMR0 interrupt is generated when the TMR0 register overflows from FFh to 00h in 8-bit mode, or from FFFFh to 0000h in 16-bit mode. This overflow sets the TMR0IF flag bit. The interrupt can be masked by clearing the TMR0IE bit (INTCON<5>). Before reenabling the interrupt, the TMR0IF bit must be cleared in software by the Interrupt Service Routine. Since Timer0 is shut down in Sleep mode, the TMR0 interrupt cannot awaken the processor from Sleep. TABLE 11-1: REGISTERS ASSOCIATED WITH TIMER0 Note: Writing to TMR0 when the prescaler is assigned to Timer0 will clear the prescaler count but will not change the prescaler assignment. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page TMR0L Timer0 Register Low Byte 54 TMR0H Timer0 Register High Byte 54 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP 53 T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 54 TRISA — TRISA6(1) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 Legend: — = unimplemented locations, read as ‘0’. Shaded cells are not used by Timer0. Note 1: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 130 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 131 PIC18F2455/2550/4455/4550 12.0 TIMER1 MODULE The Timer1 timer/counter module incorporates these features: • Software selectable operation as a 16-bit timer or counter • Readable and writable 8-bit registers (TMR1H and TMR1L) • Selectable clock source (internal or external) with device clock or Timer1 oscillator internal options • Interrupt on overflow • Module Reset on CCP Special Event Trigger • Device clock status flag (T1RUN) A simplified block diagram of the Timer1 module is shown in Figure 12-1. A block diagram of the module’s operation in Read/Write mode is shown in Figure 12-2. The module incorporates its own low-power oscillator to provide an additional clocking option. The Timer1 oscillator can also be used as a low-power clock source for the microcontroller in power-managed operation. Timer1 can also be used to provide Real-Time Clock (RTC) functionality to applications with only a minimal addition of external components and code overhead. Timer1 is controlled through the T1CON Control register (Register 12-1). It also contains the Timer1 Oscillator Enable bit (T1OSCEN). Timer1 can be enabled or disabled by setting or clearing control bit, TMR1ON (T1CON<0>). REGISTER 12-1: T1CON: TIMER1 CONTROL REGISTER R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 RD16: 16-Bit Read/Write Mode Enable bit 1 = Enables register read/write of Timer1 in one 16-bit operation 0 = Enables register read/write of Timer1 in two 8-bit operations bit 6 T1RUN: Timer1 System Clock Status bit 1 = Device clock is derived from Timer1 oscillator 0 = Device clock is derived from another source bit 5-4 T1CKPS1:T1CKPS0: Timer1 Input Clock Prescale Select bits 11 = 1:8 Prescale value 10 = 1:4 Prescale value 01 = 1:2 Prescale value 00 = 1:1 Prescale value bit 3 T1OSCEN: Timer1 Oscillator Enable bit 1 = Timer1 oscillator is enabled 0 = Timer1 oscillator is shut off The oscillator inverter and feedback resistor are turned off to eliminate power drain. bit 2 T1SYNC: Timer1 External Clock Input Synchronization Select bit When TMR1CS = 1: 1 = Do not synchronize external clock input 0 = Synchronize external clock input When TMR1CS = 0: This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0. bit 1 TMR1CS: Timer1 Clock Source Select bit 1 = External clock from RC0/T1OSO/T13CKI pin (on the rising edge) 0 = Internal clock (FOSC/4) bit 0 TMR1ON: Timer1 On bit 1 = Enables Timer1 0 = Stops Timer1 PIC18F2455/2550/4455/4550 DS39632E-page 132 © 2009 Microchip Technology Inc. 12.1 Timer1 Operation Timer1 can operate in one of these modes: • Timer • Synchronous Counter • Asynchronous Counter The operating mode is determined by the clock select bit, TMR1CS (T1CON<1>). When TMR1CS is cleared (= 0), Timer1 increments on every internal instruction cycle (FOSC/4). When the bit is set, Timer1 increments on every rising edge of the Timer1 external clock input or the Timer1 oscillator, if enabled. When Timer1 is enabled, the RC1/T1OSI/UOE and RC0/T1OSO/T13CKI pins become inputs. This means the values of TRISC<1:0> are ignored and the pins are read as ‘0’. FIGURE 12-1: TIMER1 BLOCK DIAGRAM FIGURE 12-2: TIMER1 BLOCK DIAGRAM (16-BIT READ/WRITE MODE) T1SYNC TMR1CS T1CKPS1:T1CKPS0 Sleep Input T1OSCEN(1) FOSC/4 Internal Clock On/Off Prescaler 1, 2, 4, 8 Synchronize Detect 1 0 2 T1OSO/T13CKI T1OSI 1 0 TMR1ON TMR1L TMR1 Clear TMR1 High Byte (CCP Special Event Trigger) Timer1 Oscillator Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain. On/Off Timer1 Set TMR1IF on Overflow T1SYNC TMR1CS T1CKPS1:T1CKPS0 Sleep Input T1OSCEN(1) FOSC/4 Internal Clock Prescaler 1, 2, 4, 8 Synchronize Detect 1 0 2 T1OSO/T13CKI T1OSI Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain. 1 0 TMR1L Internal Data Bus 8 Set TMR1IF on Overflow TMR1 TMR1H High Byte 8 8 8 Read TMR1L Write TMR1L 8 TMR1ON Clear TMR1 (CCP Special Event Trigger) Timer1 Oscillator On/Off Timer1 © 2009 Microchip Technology Inc. DS39632E-page 133 PIC18F2455/2550/4455/4550 12.2 Timer1 16-Bit Read/Write Mode Timer1 can be configured for 16-bit reads and writes (see Figure 12-2). When the RD16 control bit (T1CON<7>) is set, the address for TMR1H is mapped to a buffer register for the high byte of Timer1. A read from TMR1L will load the contents of the high byte of Timer1 into the Timer1 high byte buffer. This provides the user with the ability to accurately read all 16 bits of Timer1 without having to determine whether a read of the high byte, followed by a read of the low byte, has become invalid due to a rollover between reads. A write to the high byte of Timer1 must also take place through the TMR1H Buffer register. The Timer1 high byte is updated with the contents of TMR1H when a write occurs to TMR1L. This allows a user to write all 16 bits to both the high and low bytes of Timer1 at once. The high byte of Timer1 is not directly readable or writable in this mode. All reads and writes must take place through the Timer1 High Byte Buffer register. Writes to TMR1H do not clear the Timer1 prescaler. The prescaler is only cleared on writes to TMR1L. 12.3 Timer1 Oscillator An on-chip crystal oscillator circuit is incorporated between pins T1OSI (input) and T1OSO (amplifier output). It is enabled by setting the Timer1 Oscillator Enable bit, T1OSCEN (T1CON<3>). The oscillator is a low-power circuit rated for 32 kHz crystals. It will continue to run during all power-managed modes. The circuit for a typical LP oscillator is shown in Figure 12-3. Table 12-1 shows the capacitor selection for the Timer1 oscillator. The user must provide a software time delay to ensure proper start-up of the Timer1 oscillator. FIGURE 12-3: EXTERNAL COMPONENTS FOR THE TIMER1 LP OSCILLATOR TABLE 12-1: CAPACITOR SELECTION FOR THE TIMER OSCILLATOR(2,3,4) 12.3.1 USING TIMER1 AS A CLOCK SOURCE The Timer1 oscillator is also available as a clock source in power-managed modes. By setting the clock select bits, SCS1:SCS0 (OSCCON<1:0>), to ‘01’, the device switches to SEC_RUN mode. Both the CPU and peripherals are clocked from the Timer1 oscillator. If the IDLEN bit (OSCCON<7>) is cleared and a SLEEP instruction is executed, the device enters SEC_IDLE mode. Additional details are available in Section 3.0 “Power-Managed Modes”. Whenever the Timer1 oscillator is providing the clock source, the Timer1 system clock status flag, T1RUN (T1CON<6>), is set. This can be used to determine the controller’s current clocking mode. It can also indicate the clock source being currently used by the Fail-Safe Clock Monitor. If the Clock Monitor is enabled and the Timer1 oscillator fails while providing the clock, polling the T1RUN bit will indicate whether the clock is being provided by the Timer1 oscillator or another source. 12.3.2 LOW-POWER TIMER1 OPTION The Timer1 oscillator can operate at two distinct levels of power consumption based on device configuration. When the LPT1OSC Configuration bit is set, the Timer1 oscillator operates in a low-power mode. When LPT1OSC is not set, Timer1 operates at a higher power level. Power consumption for a particular mode is relatively constant, regardless of the device’s operating mode. The default Timer1 configuration is the higher power mode. As the low-power Timer1 mode tends to be more sensitive to interference, high noise environments may cause some oscillator instability. The low-power option is, therefore, best suited for low noise applications where power conservation is an important design consideration. Note: See the notes with Table 12-1 for additional information about capacitor selection. C1 C2 XTAL PIC18FXXXX T1OSI T1OSO 32.768 kHz 27 pF 27 pF Osc Type Freq C1 C2 LP 32 kHz 27 pF(1) 27 pF(1) Note 1: Microchip suggests these values as a starting point in validating the oscillator circuit. 2: Higher capacitance increases the stability of the oscillator but also increases the start-up time. 3: Since each resonator/crystal has its own characteristics, the user should consult the resonator/crystal manufacturer for appropriate values of external components. 4: Capacitor values are for design guidance only. PIC18F2455/2550/4455/4550 DS39632E-page 134 © 2009 Microchip Technology Inc. 12.3.3 TIMER1 OSCILLATOR LAYOUT CONSIDERATIONS The Timer1 oscillator circuit draws very little power during operation. Due to the low-power nature of the oscillator, it may also be sensitive to rapidly changing signals in close proximity. The oscillator circuit, shown in Figure 12-3, should be located as close as possible to the microcontroller. There should be no circuits passing within the oscillator circuit boundaries other than VSS or VDD. If a high-speed circuit must be located near the oscillator (such as the CCP1 pin in Output Compare or PWM mode, or the primary oscillator using the OSC2 pin), a grounded guard ring around the oscillator circuit, as shown in Figure 12-4, may be helpful when used on a single-sided PCB or in addition to a ground plane. FIGURE 12-4: OSCILLATOR CIRCUIT WITH GROUNDED GUARD RING 12.4 Timer1 Interrupt The TMR1 register pair (TMR1H:TMR1L) increments from 0000h to FFFFh and rolls over to 0000h. The Timer1 interrupt, if enabled, is generated on overflow which is latched in interrupt flag bit, TMR1IF (PIR1<0>). This interrupt can be enabled or disabled by setting or clearing the Timer1 Interrupt Enable bit, TMR1IE (PIE1<0>). 12.5 Resetting Timer1 Using the CCP Special Event Trigger If either of the CCP modules is configured in Compare mode to generate a Special Event Trigger (CCP1M3:CCP1M0 or CCP2M3:CCP2M0 = 1011), this signal will reset Timer1. The trigger from CCP2 will also start an A/D conversion if the A/D module is enabled (see Section 15.3.4 “Special Event Trigger” for more information). The module must be configured as either a timer or a synchronous counter to take advantage of this feature. When used this way, the CCPRH:CCPRL register pair effectively becomes a period register for Timer1. If Timer1 is running in Asynchronous Counter mode, this Reset operation may not work. In the event that a write to Timer1 coincides with a Special Event Trigger, the write operation will take precedence. 12.6 Using Timer1 as a Real-Time Clock Adding an external LP oscillator to Timer1 (such as the one described in Section 12.3 “Timer1 Oscillator”) gives users the option to include RTC functionality to their applications. This is accomplished with an inexpensive watch crystal to provide an accurate time base and several lines of application code to calculate the time. When operating in Sleep mode and using a battery or supercapacitor as a power source, it can completely eliminate the need for a separate RTC device and battery backup. The application code routine, RTCisr, shown in Example 12-1, demonstrates a simple method to increment a counter at one-second intervals using an Interrupt Service Routine. Incrementing the TMR1 register pair to overflow triggers the interrupt and calls the routine, which increments the seconds counter by one. Additional counters for minutes and hours are incremented as the previous counter overflows. Since the register pair is 16 bits wide, counting up to overflow the register directly from a 32.768 kHz clock would take 2 seconds. To force the overflow at the required one-second intervals, it is necessary to preload it. The simplest method is to set the MSb of TMR1H with a BSF instruction. Note that the TMR1L register is never preloaded or altered; doing so may introduce cumulative error over many cycles. For this method to be accurate, Timer1 must operate in Asynchronous mode and the Timer1 overflow interrupt must be enabled (PIE1<0> = 1) as shown in the routine, RTCinit. The Timer1 oscillator must also be enabled and running at all times. VDD OSC1 VSS OSC2 RC0 RC1 RC2 Note: Not drawn to scale. Note: The Special Event Triggers from the CCP2 module will not set the TMR1IF interrupt flag bit (PIR1<0>). © 2009 Microchip Technology Inc. DS39632E-page 135 PIC18F2455/2550/4455/4550 12.7 Considerations in Asynchronous Counter Mode Following a Timer1 interrupt and an update to the TMR1 registers, the Timer1 module uses a falling edge on its clock source to trigger the next register update on the rising edge. If the update is completed after the clock input has fallen, the next rising edge will not be counted. If the application can reliably update TMR1 before the timer input goes low, no additional action is needed. Otherwise, an adjusted update can be performed following a later Timer1 increment. This can be done by monitoring TMR1L within the interrupt routine until it increments, and then updating the TMR1H:TMR1L register pair while the clock is low, or one-half of the period of the clock source. Assuming that Timer1 is being used as a Real-Time Clock, the clock source is a 32.768 kHz crystal oscillator; in this case, one-half period of the clock is 15.25 μs. The Real-Time Clock application code in Example 12-1 shows a typical ISR for Timer1, as well as the optional code required if the update cannot be done reliably within the required interval. EXAMPLE 12-1: IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE RTCinit MOVLW 80h ; Preload TMR1 register pair MOVWF TMR1H ; for 1 second overflow CLRF TMR1L MOVLW b’00001111’ ; Configure for external clock, MOVWF T1CON ; Asynchronous operation, external oscillator CLRF secs ; Initialize timekeeping registers CLRF mins ; MOVLW .12 MOVWF hours BSF PIE1, TMR1IE ; Enable Timer1 interrupt RETURN RTCisr ; Insert the next 4 lines of code when TMR1 ; can not be reliably updated before clock pulse goes low BTFSC TMR1L,0 ; wait for TMR1L to become clear BRA $-2 ; (may already be clear) BTFSS TMR1L,0 ; wait for TMR1L to become set BRA $-2 ; TMR1 has just incremented ; If TMR1 update can be completed before clock pulse goes low ; Start ISR here BSF TMR1H, 7 ; Preload for 1 sec overflow BCF PIR1, TMR1IF ; Clear interrupt flag INCF secs, F ; Increment seconds MOVLW .59 ; 60 seconds elapsed? CPFSGT secs RETURN ; No, done CLRF secs ; Clear seconds INCF mins, F ; Increment minutes MOVLW .59 ; 60 minutes elapsed? CPFSGT mins RETURN ; No, done CLRF mins ; clear minutes INCF hours, F ; Increment hours MOVLW .23 ; 24 hours elapsed? CPFSGT hours RETURN ; No, done CLRF hours ; Reset hours RETURN ; Done PIC18F2455/2550/4455/4550 DS39632E-page 136 © 2009 Microchip Technology Inc. TABLE 12-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 TMR1L Timer1 Register Low Byte 54 TMR1H TImer1 Register High Byte 54 T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 54 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer1 module. Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 137 PIC18F2455/2550/4455/4550 13.0 TIMER2 MODULE The Timer2 module timer incorporates the following features: • 8-bit Timer and Period registers (TMR2 and PR2, respectively) • Readable and writable (both registers) • Software programmable prescaler (1:1, 1:4 and 1:16) • Software programmable postscaler (1:1 through 1:16) • Interrupt on TMR2 to PR2 match • Optional use as the shift clock for the MSSP module The module is controlled through the T2CON register (Register 13-1) which enables or disables the timer and configures the prescaler and postscaler. Timer2 can be shut off by clearing control bit, TMR2ON (T2CON<2>), to minimize power consumption. A simplified block diagram of the module is shown in Figure 13-1. 13.1 Timer2 Operation In normal operation, TMR2 is incremented from 00h on each clock (FOSC/4). A 2-bit counter/prescaler on the clock input gives direct input, divide-by-4 and divide-by- 16 prescale options. These are selected by the prescaler control bits, T2CKPS1:T2CKPS0 (T2CON<1:0>). The value of TMR2 is compared to that of the Period register, PR2, on each clock cycle. When the two values match, the comparator generates a match signal as the timer output. This signal also resets the value of TMR2 to 00h on the next cycle and drives the output counter/postscaler (see Section 13.2 “Timer2 Interrupt”). The TMR2 and PR2 registers are both directly readable and writable. The TMR2 register is cleared on any device Reset, while the PR2 register initializes at FFh. Both the prescaler and postscaler counters are cleared on the following events: • a write to the TMR2 register • a write to the T2CON register • any device Reset (Power-on Reset, MCLR Reset, Watchdog Timer Reset or Brown-out Reset) TMR2 is not cleared when T2CON is written. REGISTER 13-1: T2CON: TIMER2 CONTROL REGISTER U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 Unimplemented: Read as ‘0’ bit 6-3 T2OUTPS3:T2OUTPS0: Timer2 Output Postscale Select bits 0000 = 1:1 Postscale 0001 = 1:2 Postscale • • • 1111 = 1:16 Postscale bit 2 TMR2ON: Timer2 On bit 1 = Timer2 is on 0 = Timer2 is off bit 1-0 T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits 00 = Prescaler is 1 01 = Prescaler is 4 1x = Prescaler is 16 PIC18F2455/2550/4455/4550 DS39632E-page 138 © 2009 Microchip Technology Inc. 13.2 Timer2 Interrupt Timer2 can also generate an optional device interrupt. The Timer2 output signal (TMR2 to PR2 match) provides the input for the 4-bit output counter/postscaler. This counter generates the TMR2 match interrupt flag which is latched in TMR2IF (PIR1<1>). The interrupt is enabled by setting the TMR2 Match Interrupt Enable bit, TMR2IE (PIE1<1>). A range of 16 postscale options (from 1:1 through 1:16 inclusive) can be selected with the postscaler control bits, T2OUTPS3:T2OUTPS0 (T2CON<6:3>). 13.3 TMR2 Output The unscaled output of TMR2 is available primarily to the CCP modules, where it is used as a time base for operations in PWM mode. Timer2 can be optionally used as the shift clock source for the MSSP module operating in SPI mode. Additional information is provided in Section 19.0 “Master Synchronous Serial Port (MSSP) Module”. FIGURE 13-1: TIMER2 BLOCK DIAGRAM TABLE 13-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER Comparator TMR2 Output TMR2 Postscaler Prescaler PR2 2 FOSC/4 1:1 to 1:16 1:1, 1:4, 1:16 4 T2OUTPS3:T2OUTPS0 T2CKPS1:T2CKPS0 Set TMR2IF Internal Data Bus 8 Reset TMR2/PR2 8 8 (to PWM or MSSP) Match Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 TMR2 Timer2 Register 54 T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 54 PR2 Timer2 Period Register 54 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module. Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 139 PIC18F2455/2550/4455/4550 14.0 TIMER3 MODULE The Timer3 module timer/counter incorporates these features: • Software selectable operation as a 16-bit timer or counter • Readable and writable 8-bit registers (TMR3H and TMR3L) • Selectable clock source (internal or external) with device clock or Timer1 oscillator internal options • Interrupt on overflow • Module Reset on CCP Special Event Trigger A simplified block diagram of the Timer3 module is shown in Figure 14-1. A block diagram of the module’s operation in Read/Write mode is shown in Figure 14-2. The Timer3 module is controlled through the T3CON register (Register 14-1). It also selects the clock source options for the CCP modules (see Section 15.1.1 “CCP Modules and Timer Resources” for more information). REGISTER 14-1: T3CON: TIMER3 CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 RD16: 16-Bit Read/Write Mode Enable bit 1 = Enables register read/write of Timer3 in one 16-bit operation 0 = Enables register read/write of Timer3 in two 8-bit operations bit 6, 3 T3CCP2:T3CCP1: Timer3 and Timer1 to CCPx Enable bits 1x = Timer3 is the capture/compare clock source for both CCP modules 01 = Timer3 is the capture/compare clock source for CCP2; Timer1 is the capture/compare clock source for CCP1 00 = Timer1 is the capture/compare clock source for both CCP modules bit 5-4 T3CKPS1:T3CKPS0: Timer3 Input Clock Prescale Select bits 11 = 1:8 Prescale value 10 = 1:4 Prescale value 01 = 1:2 Prescale value 00 = 1:1 Prescale value bit 2 T3SYNC: Timer3 External Clock Input Synchronization Control bit (Not usable if the device clock comes from Timer1/Timer3.) When TMR3CS = 1: 1 = Do not synchronize external clock input 0 = Synchronize external clock input When TMR3CS = 0: This bit is ignored. Timer3 uses the internal clock when TMR3CS = 0. bit 1 TMR3CS: Timer3 Clock Source Select bit 1 = External clock input from Timer1 oscillator or T13CKI (on the rising edge after the first falling edge) 0 = Internal clock (FOSC/4) bit 0 TMR3ON: Timer3 On bit 1 = Enables Timer3 0 = Stops Timer3 PIC18F2455/2550/4455/4550 DS39632E-page 140 © 2009 Microchip Technology Inc. 14.1 Timer3 Operation Timer3 can operate in one of three modes: • Timer • Synchronous Counter • Asynchronous Counter The operating mode is determined by the clock select bit, TMR3CS (T3CON<1>). When TMR3CS is cleared (= 0), Timer3 increments on every internal instruction cycle (FOSC/4). When the bit is set, Timer3 increments on every rising edge of the Timer1 external clock input or the Timer1 oscillator, if enabled. As with Timer1, the RC1/T1OSI/UOE and RC0/ T1OSO/T13CKI pins become inputs when the Timer1 oscillator is enabled. This means the values of TRISC<1:0> are ignored and the pins are read as ‘0’. FIGURE 14-1: TIMER3 BLOCK DIAGRAM FIGURE 14-2: TIMER3 BLOCK DIAGRAM (16-BIT READ/WRITE MODE) T3SYNC TMR3CS T3CKPS1:T3CKPS0 Sleep Input T1OSCEN(1) FOSC/4 Internal Clock Prescaler 1, 2, 4, 8 Synchronize Detect 1 0 2 T1OSO/T13CKI T1OSI 1 0 TMR3ON TMR3L Set TMR3IF on Overflow TMR3 High Byte Timer1 Oscillator Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain. On/Off Timer3 CCP1/CCP2 Special Event Trigger CCP1/CCP2 Select from T3CON<6,3> Clear TMR3 Timer1 Clock Input T3SYNC TMR3CS T3CKPS1:T3CKPS0 Sleep Input T1OSCEN(1) FOSC/4 Internal Clock Prescaler 1, 2, 4, 8 Synchronize Detect 1 0 2 T1OSO/T13CKI T1OSI Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain. 1 0 TMR3L Internal Data Bus 8 Set TMR3IF on Overflow TMR3 TMR3H High Byte 8 8 8 Read TMR1L Write TMR1L 8 TMR3ON CCP1/CCP2 Special Event Trigger Timer1 Oscillator On/Off Timer3 Timer1 Clock Input CCP1/CCP2 Select from T3CON<6,3> Clear TMR3 © 2009 Microchip Technology Inc. DS39632E-page 141 PIC18F2455/2550/4455/4550 14.2 Timer3 16-Bit Read/Write Mode Timer3 can be configured for 16-bit reads and writes (see Figure 14-2). When the RD16 control bit (T3CON<7>) is set, the address for TMR3H is mapped to a buffer register for the high byte of Timer3. A read from TMR3L will load the contents of the high byte of Timer3 into the Timer3 high byte buffer. This provides the user with the ability to accurately read all 16 bits of Timer1 without having to determine whether a read of the high byte, followed by a read of the low byte, has become invalid due to a rollover between reads. A write to the high byte of Timer3 must also take place through the TMR3H Buffer register. The Timer3 high byte is updated with the contents of TMR3H when a write occurs to TMR3L. This allows a user to write all 16 bits to both the high and low bytes of Timer3 at once. The high byte of Timer3 is not directly readable or writable in this mode. All reads and writes must take place through the Timer3 High Byte Buffer register. Writes to TMR3H do not clear the Timer3 prescaler. The prescaler is only cleared on writes to TMR3L. 14.3 Using the Timer1 Oscillator as the Timer3 Clock Source The Timer1 internal oscillator may be used as the clock source for Timer3. The Timer1 oscillator is enabled by setting the T1OSCEN (T1CON<3>) bit. To use it as the Timer3 clock source, the TMR3CS bit must also be set. As previously noted, this also configures Timer3 to increment on every rising edge of the oscillator source. The Timer1 oscillator is described in Section 12.0 “Timer1 Module”. 14.4 Timer3 Interrupt The TMR3 register pair (TMR3H:TMR3L) increments from 0000h to FFFFh and overflows to 0000h. The Timer3 interrupt, if enabled, is generated on overflow and is latched in interrupt flag bit, TMR3IF (PIR2<1>). This interrupt can be enabled or disabled by setting or clearing the Timer3 Interrupt Enable bit, TMR3IE (PIE2<1>). 14.5 Resetting Timer3 Using the CCP Special Event Trigger If the CCP2 module is configured to generate a Special Event Trigger in Compare mode (CCP2M3:CCP2M0 = 1011), this signal will reset Timer3. It will also start an A/D conversion if the A/D module is enabled (see Section 15.3.4 “Special Event Trigger” for more information.). The module must be configured as either a timer or synchronous counter to take advantage of this feature. When used this way, the CCPR2H:CCPR2L register pair effectively becomes a period register for Timer3. If Timer3 is running in Asynchronous Counter mode, the Reset operation may not work. In the event that a write to Timer3 coincides with a Special Event Trigger from a CCP module, the write will take precedence. TABLE 14-1: REGISTERS ASSOCIATED WITH TIMER3 AS A TIMER/COUNTER Note: The Special Event Triggers from the CCP2 module will not set the TMR3IF interrupt flag bit (PIR2<1>). Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 TMR3L Timer3 Register Low Byte 55 TMR3H Timer3 Register High Byte 55 T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 54 T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer3 module. PIC18F2455/2550/4455/4550 DS39632E-page 142 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 143 PIC18F2455/2550/4455/4550 15.0 CAPTURE/COMPARE/PWM (CCP) MODULES PIC18F2455/2550/4455/4550 devices all have two CCP (Capture/Compare/PWM) modules. Each module contains a 16-bit register, which can operate as a 16-bit Capture register, a 16-bit Compare register or a PWM Master/Slave Duty Cycle register. In 28-pin devices, the two standard CCP modules (CCP1 and CCP2) operate as described in this chapter. In 40/44-pin devices, CCP1 is implemented as an Enhanced CCP module, with standard Capture and Compare modes and Enhanced PWM modes. The ECCP implementation is discussed in Section 16.0 “Enhanced Capture/Compare/PWM (ECCP) Module”. The Capture and Compare operations described in this chapter apply to all standard and Enhanced CCP modules. Note: Throughout this section and Section 16.0 “Enhanced Capture/Compare/PWM (ECCP) Module”, references to the register and bit names for CCP modules are referred to generically by the use of ‘x’ or ‘y’ in place of the specific module number. Thus, “CCPxCON” might refer to the control register for CCP1, CCP2 or ECCP1. “CCPxCON” is used throughout these sections to refer to the module control register regardless of whether the CCP module is a standard or Enhanced implementation. REGISTER 15-1: CCPxCON: STANDARD CCPx CONTROL REGISTER U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 —(1) —(1) DCxB1 DCxB0 CCPxM3 CCPxM2 CCPxM1 CCPxM0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-6 Unimplemented: Read as ‘0’(1) bit 5-4 DCxB1:DCxB0: PWM Duty Cycle Bit 1 and Bit 0 for CCPx Module Capture mode: Unused. Compare mode: Unused. PWM mode: These bits are the two LSbs (bit 1 and bit 0) of the 10-bit PWM duty cycle. The eight MSbs of the duty cycle are found in CCPR1L. bit 3-0 CCPxM3:CCPxM0: CCPx Module Mode Select bits 0000 = Capture/Compare/PWM disabled (resets CCPx module) 0001 = Reserved 0010 = Compare mode: toggle output on match (CCPxIF bit is set) 0011 = Reserved 0100 = Capture mode: every falling edge 0101 = Capture mode: every rising edge 0110 = Capture mode: every 4th rising edge 0111 = Capture mode: every 16th rising edge 1000 = Compare mode: initialize CCPx pin low; on compare match, force CCPx pin high (CCPxIF bit is set) 1001 = Compare mode: initialize CCPx pin high; on compare match, force CCPx pin low (CCPxIF bit is set) 1010 = Compare mode: generate software interrupt on compare match (CCPxIF bit is set, CCPx pin reflects I/O state) 1011 = Compare mode: trigger special event, reset timer, start A/D conversion on CCPx match (CCPxIF bit is set) 11xx = PWM mode Note 1: These bits are not implemented on 28-pin devices and are read as ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 144 © 2009 Microchip Technology Inc. 15.1 CCP Module Configuration Each Capture/Compare/PWM module is associated with a control register (generically, CCPxCON) and a data register (CCPRx). The data register, in turn, is comprised of two 8-bit registers: CCPRxL (low byte) and CCPRxH (high byte). All registers are both readable and writable. 15.1.1 CCP MODULES AND TIMER RESOURCES The CCP modules utilize Timers 1, 2 or 3, depending on the mode selected. Timer1 and Timer3 are available to modules in Capture or Compare modes, while Timer2 is available for modules in PWM mode. TABLE 15-1: CCP MODE – TIMER RESOURCE The assignment of a particular timer to a module is determined by the Timer to CCP enable bits in the T3CON register (Register 14-1). Both modules may be active at any given time and may share the same timer resource if they are configured to operate in the same mode (Capture/Compare or PWM) at the same time. The interactions between the two modules are summarized in Figure 15-2. In Timer1 in Asynchronous Counter mode, the capture operation will not work. 15.1.2 CCP2 PIN ASSIGNMENT The pin assignment for CCP2 (capture input, compare and PWM output) can change, based on device configuration. The CCP2MX Configuration bit determines which pin CCP2 is multiplexed to. By default, it is assigned to RC1 (CCP2MX = 1). If the Configuration bit is cleared, CCP2 is multiplexed with RB3. Changing the pin assignment of CCP2 does not automatically change any requirements for configuring the port pin. Users must always verify that the appropriate TRIS register is configured correctly for CCP2 operation, regardless of where it is located. TABLE 15-2: INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES CCP/ECCP Mode Timer Resource Capture Compare PWM Timer1 or Timer3 Timer1 or Timer3 Timer2 CCP1 Mode CCP2 Mode Interaction Capture Capture Each module can use TMR1 or TMR3 as the time base. The time base can be different for each CCP. Capture Compare CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3 (depending upon which time base is used). Automatic A/D conversions on trigger event can also be done. Operation of CCP1 could be affected if it is using the same timer as a time base. Compare Capture CCP1 be configured for the Special Event Trigger to reset TMR1 or TMR3 (depending upon which time base is used). Operation of CCP2 could be affected if it is using the same timer as a time base. Compare Compare Either module can be configured for the Special Event Trigger to reset the time base. Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if both modules are using the same time base. Capture PWM(1) None Compare PWM(1) None PWM(1) Capture None PWM(1) Compare None PWM(1) PWM Both PWMs will have the same frequency and update rate (TMR2 interrupt). Note 1: Includes standard and Enhanced PWM operation. © 2009 Microchip Technology Inc. DS39632E-page 145 PIC18F2455/2550/4455/4550 15.2 Capture Mode In Capture mode, the CCPRxH:CCPRxL register pair captures the 16-bit value of the TMR1 or TMR3 registers when an event occurs on the corresponding CCPx pin. An event is defined as one of the following: • every falling edge • every rising edge • every 4th rising edge • every 16th rising edge The event is selected by the mode select bits, CCPxM3:CCPxM0 (CCPxCON<3:0>). When a capture is made, the interrupt request flag bit, CCPxIF, is set; it must be cleared in software. If another capture occurs before the value in register CCPRx is read, the old captured value is overwritten by the new captured value. 15.2.1 CCP PIN CONFIGURATION In Capture mode, the appropriate CCPx pin should be configured as an input by setting the corresponding TRIS direction bit. 15.2.2 TIMER1/TIMER3 MODE SELECTION The timers that are to be used with the capture feature (Timer1 and/or Timer3) must be running in Timer mode or Synchronized Counter mode. In Asynchronous Counter mode, the capture operation will not work. The timer to be used with each CCP module is selected in the T3CON register (see Section 15.1.1 “CCP Modules and Timer Resources”). 15.2.3 SOFTWARE INTERRUPT When the Capture mode is changed, a false capture interrupt may be generated. The user should keep the CCPxIE interrupt enable bit clear to avoid false interrupts. The interrupt flag bit, CCPxIF, should also be cleared following any such change in operating mode. 15.2.4 CCP PRESCALER There are four prescaler settings in Capture mode. They are specified as part of the operating mode selected by the mode select bits (CCPxM3:CCPxM0). Whenever the CCP module is turned off or Capture mode is disabled, the prescaler counter is cleared. This means that any Reset will clear the prescaler counter. Switching from one capture prescaler to another may generate an interrupt. Also, the prescaler counter will not be cleared, therefore, the first capture may be from a non-zero prescaler. Example 15-1 shows the recommended method for switching between capture prescalers. This example also clears the prescaler counter and will not generate the “false” interrupt. EXAMPLE 15-1: CHANGING BETWEEN CAPTURE PRESCALERS (CCP2 SHOWN) FIGURE 15-1: CAPTURE MODE OPERATION BLOCK DIAGRAM Note: If RB3/CCP2 or RC1/CCP2 is configured as an output, a write to the port can cause a capture condition. CLRF CCP2CON ; Turn CCP module off MOVLW NEW_CAPT_PS ; Load WREG with the ; new prescaler mode ; value and CCP ON MOVWF CCP2CON ; Load CCP2CON with ; this value CCPR1H CCPR1L TMR1H TMR1L Set CCP1IF TMR3 Enable Q1:Q4 CCP1CON<3:0> CCP1 pin Prescaler ÷ 1, 4, 16 and Edge Detect TMR1 Enable T3CCP2 T3CCP2 CCPR2H CCPR2L TMR1H TMR1L Set CCP2IF TMR3 Enable CCP2CON<3:0> CCP2 pin Prescaler ÷ 1, 4, 16 TMR3H TMR3L TMR1 Enable T3CCP2 T3CCP1 T3CCP2 T3CCP1 TMR3H TMR3L and Edge Detect 4 4 4 PIC18F2455/2550/4455/4550 DS39632E-page 146 © 2009 Microchip Technology Inc. 15.3 Compare Mode In Compare mode, the 16-bit CCPRx register value is constantly compared against either the TMR1 or TMR3 register pair value. When a match occurs, the CCPx pin can be: • driven high • driven low • toggled (high-to-low or low-to-high) • remain unchanged (that is, reflects the state of the I/O latch) The action on the pin is based on the value of the mode select bits (CCPxM3:CCPxM0). At the same time, the interrupt flag bit, CCPxIF, is set. 15.3.1 CCP PIN CONFIGURATION The user must configure the CCPx pin as an output by clearing the appropriate TRIS bit. 15.3.2 TIMER1/TIMER3 MODE SELECTION Timer1 and/or Timer3 must be running in Timer mode, or Synchronized Counter mode, if the CCP module is using the compare feature. In Asynchronous Counter mode, the compare operation may not work. 15.3.3 SOFTWARE INTERRUPT MODE When the Generate Software Interrupt mode is chosen (CCPxM3:CCPxM0 = 1010), the corresponding CCPx pin is not affected. Only a CCP interrupt is generated, if enabled, and the CCPxIE bit is set. 15.3.4 SPECIAL EVENT TRIGGER Both CCP modules are equipped with a Special Event Trigger. This is an internal hardware signal generated in Compare mode to trigger actions by other modules. The Special Event Trigger is enabled by selecting the Compare Special Event Trigger mode (CCPxM3:CCPxM0 = 1011). For either CCP module, the Special Event Trigger resets the Timer register pair for whichever timer resource is currently assigned as the module’s time base. This allows the CCPRx registers to serve as a programmable Period register for either timer. The Special Event Trigger for CCP2 can also start an A/D conversion. In order to do this, the A/D converter must already be enabled. FIGURE 15-2: COMPARE MODE OPERATION BLOCK DIAGRAM Note: Clearing the CCP2CON register will force the RB3 or RC1 compare output latch (depending on device configuration) to the default low level. This is not the PORTB or PORTC I/O data latch. CCPR1H CCPR1L TMR1H TMR1L Comparator S Q R Output Logic Special Event Trigger Set CCP1IF CCP1 pin TRIS CCP1CON<3:0> Output Enable TMR3H TMR3L CCPR2H CCPR2L Comparator 1 0 T3CCP2 T3CCP1 Set CCP2IF 1 0 Compare 4 (Timer1/Timer3 Reset) S Q R Output Logic Special Event Trigger CCP2 pin TRIS CCP2CON<3:0> 4 Output Enable (Timer1/Timer3 Reset, A/D Trigger) Match Compare Match © 2009 Microchip Technology Inc. DS39632E-page 147 PIC18F2455/2550/4455/4550 TABLE 15-3: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, TIMER1 AND TIMER3 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 RCON IPEN SBOREN(1) — RI TO PD POR BOR 54 PIR1 SPPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 TMR1L Timer1 Register Low Byte 54 TMR1H Timer1 Register High Byte 54 T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 54 TMR3H Timer3 Register High Byte 55 TMR3L Timer3 Register Low Byte 55 T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 55 CCPR1L Capture/Compare/PWM Register 1 Low Byte 55 CCPR1H Capture/Compare/PWM Register 1 High Byte 55 CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 55 CCPR2L Capture/Compare/PWM Register 2 Low Byte 55 CCPR2H Capture/Compare/PWM Register 2 High Byte 55 CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by Capture/Compare, Timer1 or Timer3. Note 1: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 2: These bits are unimplemented on 28-pin devices; always maintain these bits clear. PIC18F2455/2550/4455/4550 DS39632E-page 148 © 2009 Microchip Technology Inc. 15.4 PWM Mode In Pulse-Width Modulation (PWM) mode, the CCPx pin produces up to a 10-bit resolution PWM output. Since the CCP2 pin is multiplexed with a PORTB or PORTC data latch, the appropriate TRIS bit must be cleared to make the CCP2 pin an output. Figure 15-3 shows a simplified block diagram of the CCP module in PWM mode. For a step-by-step procedure on how to set up the CCP module for PWM operation, see Section 15.4.4 “Setup for PWM Operation”. FIGURE 15-3: SIMPLIFIED PWM BLOCK DIAGRAM A PWM output (Figure 15-4) has a time base (period) and a time that the output stays high (duty cycle). The frequency of the PWM is the inverse of the period (1/period). FIGURE 15-4: PWM OUTPUT 15.4.1 PWM PERIOD The PWM period is specified by writing to the PR2 register. The PWM period can be calculated using the following formula: EQUATION 15-1: PWM frequency is defined as 1/[PWM period]. When TMR2 is equal to PR2, the following three events occur on the next increment cycle: • TMR2 is cleared • The CCPx pin is set (exception: if PWM duty cycle = 0%, the CCPx pin will not be set) • The PWM duty cycle is latched from CCPRxL into CCPRxH 15.4.2 PWM DUTY CYCLE The PWM duty cycle is specified by writing to the CCPRxL register and to the CCPxCON<5:4> bits. Up to 10-bit resolution is available. The CCPRxL contains the eight MSbs and the CCPxCON<5:4> bits contain the two LSbs. This 10-bit value is represented by CCPRxL:CCPxCON<5:4>. The following equation is used to calculate the PWM duty cycle in time: EQUATION 15-2: CCPRxL and CCPxCON<5:4> can be written to at any time, but the duty cycle value is not latched into CCPRxH until after a match between PR2 and TMR2 occurs (i.e., the period is complete). In PWM mode, CCPRxH is a read-only register. Note: Clearing the CCP2CON register will force the RB3 or RC1 output latch (depending on device configuration) to the default low level. This is not the PORTB or PORTC I/O data latch. CCPRxL CCPRxH (Slave) Comparator TMR2 Comparator PR2 (Note 1) R Q S Duty Cycle Registers CCPxCON<5:4> Clear Timer, CCPx pin and latch D.C. Note 1: The 8-bit TMR2 value is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler, to create the 10-bit time base. CCPx Corresponding TRIS bit Output Period Duty Cycle TMR2 = PR2 TMR2 = Duty Cycle TMR2 = PR2 Note: The Timer2 postscalers (see Section 13.0 “Timer2 Module”) are not used in the determination of the PWM frequency. The postscaler could be used to have a servo update rate at a different frequency than the PWM output. PWM Period = [(PR2) + 1] • 4 • TOSC • (TMR2 Prescale Value) PWM Duty Cycle = (CCPRXL:CCPXCON<5:4>) • TOSC • (TMR2 Prescale Value) © 2009 Microchip Technology Inc. DS39632E-page 149 PIC18F2455/2550/4455/4550 The CCPRxH register and a 2-bit internal latch are used to double-buffer the PWM duty cycle. This double-buffering is essential for glitchless PWM operation. When the CCPRxH and 2-bit latch match TMR2, concatenated with an internal 2-bit Q clock or 2 bits of the TMR2 prescaler, the CCPx pin is cleared. The maximum PWM resolution (bits) for a given PWM frequency is given by the equation: EQUATION 15-3: TABLE 15-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz 15.4.3 PWM AUTO-SHUTDOWN (CCP1 ONLY) The PWM auto-shutdown features of the Enhanced CCP module are also available to CCP1 in 28-pin devices. The operation of this feature is discussed in detail in Section 16.4.7 “Enhanced PWM Auto-Shutdown”. Auto-shutdown features are not available for CCP2. 15.4.4 SETUP FOR PWM OPERATION The following steps should be taken when configuring the CCPx module for PWM operation: 1. Set the PWM period by writing to the PR2 register. 2. Set the PWM duty cycle by writing to the CCPRxL register and CCPxCON<5:4> bits. 3. Make the CCPx pin an output by clearing the appropriate TRIS bit. 4. Set the TMR2 prescale value, then enable Timer2 by writing to T2CON. 5. Configure the CCPx module for PWM operation. Note: If the PWM duty cycle value is longer than the PWM period, the CCPx pin will not be cleared. FOSC FPWM ⎝---------------⎠ log⎛ ⎞ = -------l--o---g----(--2----)-------bits PWM Resolution (max) PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz Timer Prescaler (1, 4, 16) 16 4 1 1 1 1 PR2 Value FFh FFh FFh 3Fh 1Fh 17h Maximum Resolution (bits) 10 10 10 8 7 6.58 PIC18F2455/2550/4455/4550 DS39632E-page 150 © 2009 Microchip Technology Inc. TABLE 15-5: REGISTERS ASSOCIATED WITH PWM AND TIMER2 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 RCON IPEN SBOREN(1) — RI TO PD POR BOR 54 PIR1 SPPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 TMR2 Timer2 Register 54 PR2 Timer2 Period Register 54 T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 54 CCPR1L Capture/Compare/PWM Register 1 Low Byte 55 CCPR1H Capture/Compare/PWM Register 1 High Byte 55 CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 55 CCPR2L Capture/Compare/PWM Register 2 Low Byte 55 CCPR2H Capture/Compare/PWM Register 2 High Byte 55 CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 55 ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 55 ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PWM or Timer2. Note 1: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 2: These bits are unimplemented on 28-pin devices; always maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 151 PIC18F2455/2550/4455/4550 16.0 ENHANCED CAPTURE/COMPARE/PWM (ECCP) MODULE In 28-pin devices, CCP1 is implemented as a standard CCP module with Enhanced PWM capabilities. These include the provision for 2 or 4 output channels, user-selectable polarity, dead-band control and automatic shutdown and restart. The Enhanced features are discussed in detail in Section 16.4 “Enhanced PWM Mode”. Capture, Compare and single output PWM functions of the ECCP module are the same as described for the standard CCP module. The control register for the Enhanced CCP module is shown in Register 16-1. It differs from the CCPxCON registers in 28-pin devices in that the two Most Significant bits are implemented to control PWM functionality. Note: The ECCP module is implemented only in 40/44-pin devices. REGISTER 16-1: CCP1CON: ECCP CONTROL REGISTER (40/44-PIN DEVICES) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-6 P1M1:P1M0: Enhanced PWM Output Configuration bits If CCP1M3:CCP1M2 = 00, 01, 10: xx = P1A assigned as Capture/Compare input/output; P1B, P1C, P1D assigned as port pins If CCP1M3:CCP1M2 = 11: 00 = Single output: P1A modulated; P1B, P1C, P1D assigned as port pins 01 = Full-bridge output forward: P1D modulated; P1A active; P1B, P1C inactive 10 = Half-bridge output: P1A, P1B modulated with dead-band control; P1C, P1D assigned as port pins 11 = Full-bridge output reverse: P1B modulated; P1C active; P1A, P1D inactive bit 5-4 DC1B1:DC1B0: PWM Duty Cycle Bit 1 and Bit 0 Capture mode: Unused. Compare mode: Unused. PWM mode: These bits are the two LSbs of the 10-bit PWM duty cycle. The eight MSbs of the duty cycle are found in CCPR1L. bit 3-0 CCP1M3:CCP1M0: Enhanced CCP Mode Select bits 0000 = Capture/Compare/PWM off (resets ECCP module) 0001 = Reserved 0010 = Compare mode, toggle output on match 0011 = Capture mode 0100 = Capture mode, every falling edge 0101 = Capture mode, every rising edge 0110 = Capture mode, every 4th rising edge 0111 = Capture mode, every 16th rising edge 1000 = Compare mode, initialize CCP1 pin low, set output on compare match (set CCP1IF) 1001 = Compare mode, initialize CCP1 pin high, clear output on compare match (set CCP1IF) 1010 = Compare mode, generate software interrupt only, CCP1 pin reverts to I/O state 1011 = Compare mode, trigger special event (CCP1 resets TMR1 or TMR3, sets CCP1IF bit) 1100 = PWM mode: P1A, P1C active-high; P1B, P1D active-high 1101 = PWM mode: P1A, P1C active-high; P1B, P1D active-low 1110 = PWM mode: P1A, P1C active-low; P1B, P1D active-high 1111 = PWM mode: P1A, P1C active-low; P1B, P1D active-low PIC18F2455/2550/4455/4550 DS39632E-page 152 © 2009 Microchip Technology Inc. In addition to the expanded range of modes available through the CCP1CON register, the ECCP module has two additional registers associated with Enhanced PWM operation and auto-shutdown features. They are: • ECCP1DEL (PWM Dead-Band Delay) • ECCP1AS (ECCP Auto-Shutdown Control) 16.1 ECCP Outputs and Configuration The Enhanced CCP module may have up to four PWM outputs, depending on the selected operating mode. These outputs, designated P1A through P1D, are multiplexed with I/O pins on PORTC and PORTD. The outputs that are active depend on the CCP operating mode selected. The pin assignments are summarized in Table 16-1. To configure the I/O pins as PWM outputs, the proper PWM mode must be selected by setting the P1M1:P1M0 and CCP1M3:CCP1M0 bits. The appropriate TRISC and TRISD direction bits for the port pins must also be set as outputs. 16.1.1 ECCP MODULES AND TIMER RESOURCES Like the standard CCP modules, the ECCP module can utilize Timers 1, 2 or 3, depending on the mode selected. Timer1 and Timer3 are available for modules in Capture or Compare modes, while Timer2 is available for modules in PWM mode. Interactions between the standard and Enhanced CCP modules are identical to those described for standard CCP modules. Additional details on timer resources are provided in Section 15.1.1 “CCP Modules and Timer Resources”. 16.2 Capture and Compare Modes Except for the operation of the Special Event Trigger discussed below, the Capture and Compare modes of the ECCP module are identical in operation to that of CCP. These are discussed in detail in Section 15.2 “Capture Mode” and Section 15.3 “Compare Mode”. 16.2.1 SPECIAL EVENT TRIGGER The Special Event Trigger output of ECCP resets the TMR1 or TMR3 register pair, depending on which timer resource is currently selected. This allows the CCPR1H:CCPR1L registers to effectively be a 16-bit programmable period register for Timer1 or Timer3. 16.3 Standard PWM Mode When configured in Single Output mode, the ECCP module functions identically to the standard CCP module in PWM mode as described in Section 15.4 “PWM Mode”. This is also sometimes referred to as “Compatible CCP” mode, as in Table 16-1. TABLE 16-1: PIN ASSIGNMENTS FOR VARIOUS ECCP1 MODES Note: When setting up single output PWM operations, users are free to use either of the processes described in Section 15.4.4 “Setup for PWM Operation” or Section 16.4.9 “Setup for PWM Operation”. The latter is more generic but will work for either single or multi-output PWM. ECCP Mode CCP1CON Configuration RC2 RD5 RD6 RD7 All PIC18F4455/4550 devices: Compatible CCP 00xx 11xx CCP1 RD5/SPP5 RD6/SPP6 RD7/SPP7 Dual PWM 10xx 11xx P1A P1B RD6/SPP6 RD7/SPP7 Quad PWM x1xx 11xx P1A P1B P1C P1D Legend: x = Don’t care. Shaded cells indicate pin assignments not used by ECCP in a given mode. © 2009 Microchip Technology Inc. DS39632E-page 153 PIC18F2455/2550/4455/4550 16.4 Enhanced PWM Mode The Enhanced PWM mode provides additional PWM output options for a broader range of control applications. The module is a backward compatible version of the standard CCP module and offers up to four outputs, designated P1A through P1D. Users are also able to select the polarity of the signal (either active-high or active-low). The module’s output mode and polarity are configured by setting the P1M1:P1M0 and CCP1M3:CCP1M0 bits of the CCP1CON register. Figure 16-1 shows a simplified block diagram of PWM operation. All control registers are double-buffered and are loaded at the beginning of a new PWM cycle (the period boundary when Timer2 resets) in order to prevent glitches on any of the outputs. The exception is the PWM Dead-Band Delay register, ECCP1DEL, which is loaded at either the duty cycle boundary or the boundary period (whichever comes first). Because of the buffering, the module waits until the assigned timer resets instead of starting immediately. This means that Enhanced PWM waveforms do not exactly match the standard PWM waveforms, but are instead offset by one full instruction cycle (4 TOSC). As before, the user must manually configure the appropriate TRIS bits for output. 16.4.1 PWM PERIOD The PWM period is specified by writing to the PR2 register. The PWM period can be calculated using the following equation: EQUATION 16-1: PWM frequency is defined as 1/ [PWM period]. When TMR2 is equal to PR2, the following three events occur on the next increment cycle: • TMR2 is cleared • The CCP1 pin is set (if PWM duty cycle = 0%, the CCP1 pin will not be set) • The PWM duty cycle is copied from CCPR1L into CCPR1H FIGURE 16-1: SIMPLIFIED BLOCK DIAGRAM OF THE ENHANCED PWM MODULE Note: The Timer2 postscaler (see Section 13.0 “Timer2 Module”) is not used in the determination of the PWM frequency. The postscaler could be used to have a servo update rate at a different frequency than the PWM output. PWM Period = [(PR2) + 1] • 4 • TOSC • (TMR2 Prescale Value) CCPR1L CCPR1H (Slave) Comparator TMR2 Comparator PR2 (Note 1) R Q S Duty Cycle Registers CCP1CON<5:4> Clear Timer, set CCP1 pin and latch D.C. Note: The 8-bit TMR2 register is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler, to create the 10-bit time base. TRISD<4> CCP1/P1A TRISD<5> P1B TRISD<6> TRISD<7> P1D Output Controller P1M1:P1M0 2 CCP1M3:CCP1M0 4 ECCP1DEL CCP1/P1A P1B P1C P1D P1C PIC18F2455/2550/4455/4550 DS39632E-page 154 © 2009 Microchip Technology Inc. 16.4.2 PWM DUTY CYCLE The PWM duty cycle is specified by writing to the CCPR1L register and to the CCP1CON<5:4> bits. Up to 10-bit resolution is available. The CCPR1L contains the eight MSbs and the CCP1CON<5:4> contains the two LSbs. This 10-bit value is represented by CCPR1L:CCP1CON<5:4>. The PWM duty cycle is calculated by the following equation. EQUATION 16-2: CCPR1L and CCP1CON<5:4> can be written to at any time, but the duty cycle value is not copied into CCPR1H until a match between PR2 and TMR2 occurs (i.e., the period is complete). In PWM mode, CCPR1H is a read-only register. The CCPR1H register and a 2-bit internal latch are used to double-buffer the PWM duty cycle. This double-buffering is essential for glitchless PWM operation. When the CCPR1H and 2-bit latch match TMR2, concatenated with an internal 2-bit Q clock or two bits of the TMR2 prescaler, the CCP1 pin is cleared. The maximum PWM resolution (bits) for a given PWM frequency is given by the following equation. EQUATION 16-3: 16.4.3 PWM OUTPUT CONFIGURATIONS The P1M1:P1M0 bits in the CCP1CON register allow one of four configurations: • Single Output • Half-Bridge Output • Full-Bridge Output, Forward mode • Full-Bridge Output, Reverse mode The Single Output mode is the standard PWM mode discussed in Section 16.4 “Enhanced PWM Mode”. The Half-Bridge and Full-Bridge Output modes are covered in detail in the sections that follow. The general relationship of the outputs in all configurations is summarized in Figure 16-2 and Figure 16-3. TABLE 16-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz PWM Duty Cycle = (CCPR1L:CCP1CON<5:4> • TOSC • (TMR2 Prescale Value) Note: If the PWM duty cycle value is longer than the PWM period, the CCP1 pin will not be cleared. ( ) PWM Resolution (max) = FOSC FPWM log log(2) bits PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz Timer Prescaler (1, 4, 16) 16 4 1 1 1 1 PR2 Value FFh FFh FFh 3Fh 1Fh 17h Maximum Resolution (bits) 10 10 10 8 7 6.58 © 2009 Microchip Technology Inc. DS39632E-page 155 PIC18F2455/2550/4455/4550 FIGURE 16-2: PWM OUTPUT RELATIONSHIPS (ACTIVE-HIGH STATE) FIGURE 16-3: PWM OUTPUT RELATIONSHIPS (ACTIVE-LOW STATE) 0 Period 00 10 01 11 SIGNAL PR2 + 1 CCP1CON <7:6> P1A Modulated P1A Modulated P1B Modulated P1A Active P1B Inactive P1C Inactive P1D Modulated P1A Inactive P1B Modulated P1C Active P1D Inactive Duty Cycle (Single Output) (Half-Bridge) (Full-Bridge, Forward) (Full-Bridge, Reverse) Delay(1) Delay(1) 0 Period 00 10 01 11 SIGNAL PR2 + 1 CCP1CON <7:6> P1A Modulated P1A Modulated P1B Modulated P1A Active P1B Inactive P1C Inactive P1D Modulated P1A Inactive P1B Modulated P1C Active P1D Inactive Duty Cycle (Single Output) (Half-Bridge) (Full-Bridge, Forward) (Full-Bridge, Reverse) Delay(1) Delay(1) Relationships: • Period = 4 * TOSC * (PR2 + 1) * (TMR2 Prescale Value) • Duty Cycle = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value) • Delay = 4 * TOSC * (ECCP1DEL<6:0>) Note 1: Dead-band delay is programmed using the ECCP1DEL register (Section 16.4.6 “Programmable Dead-Band Delay”). PIC18F2455/2550/4455/4550 DS39632E-page 156 © 2009 Microchip Technology Inc. 16.4.4 HALF-BRIDGE MODE In the Half-Bridge Output mode, two pins are used as outputs to drive push-pull loads. The PWM output signal is output on the P1A pin, while the complementary PWM output signal is output on the P1B pin (Figure 16-4). This mode can be used for half-bridge applications, as shown in Figure 16-5, or for full-bridge applications where four power switches are being modulated with two PWM signals. In Half-Bridge Output mode, the programmable dead-band delay can be used to prevent shoot-through current in half-bridge power devices. The value of bits PDC6:PDC0 sets the number of instruction cycles before the output is driven active. If the value is greater than the duty cycle, the corresponding output remains inactive during the entire cycle. See Section 16.4.6 “Programmable Dead-Band Delay” for more details of the dead-band delay operations. Since the P1A and P1B outputs are multiplexed with the PORTC<2> and PORTD<5> data latches, the TRISC<2> and TRISD<5> bits must be cleared to configure P1A and P1B as outputs. FIGURE 16-4: HALF-BRIDGE PWM OUTPUT FIGURE 16-5: EXAMPLES OF HALF-BRIDGE OUTPUT MODE APPLICATIONS Period Duty Cycle td td (1) P1A(2) P1B(2) td = Dead-Band Delay Period (1) (1) Note 1: At this time, the TMR2 register is equal to the PR2 register. 2: Output signals are shown as active-high. PIC18FX455/X550 P1A P1B FET Driver FET Driver V+ VLoad + V- + VFET Driver FET Driver V+ VLoad FET Driver FET Driver PIC18FX455/X550 P1A P1B Standard Half-Bridge Circuit (“Push-Pull”) Half-Bridge Output Driving a Full-Bridge Circuit © 2009 Microchip Technology Inc. DS39632E-page 157 PIC18F2455/2550/4455/4550 16.4.5 FULL-BRIDGE MODE In Full-Bridge Output mode, four pins are used as outputs; however, only two outputs are active at a time. In the Forward mode, pin P1A is continuously active and pin P1D is modulated. In the Reverse mode, pin P1C is continuously active and pin P1B is modulated. These are illustrated in Figure 16-6. P1A, P1B, P1C and P1D outputs are multiplexed with the PORTC<2>, PORTD<5>, PORTD<6> and PORTD<7> data latches. The TRISC<2>, TRISD<5>, TRISD<6> and TRISD<7> bits must be cleared to make the P1A, P1B, P1C and P1D pins outputs. FIGURE 16-6: FULL-BRIDGE PWM OUTPUT Period Duty Cycle P1A(2) P1B(2) P1C(2) P1D(2) Forward Mode (1) Period Duty Cycle P1A(2) P1C(2) P1D(2) P1B(2) Reverse Mode (1) (1) (1) Note 1: At this time, the TMR2 register is equal to the PR2 register. Note 2: Output signal is shown as active-high. PIC18F2455/2550/4455/4550 DS39632E-page 158 © 2009 Microchip Technology Inc. FIGURE 16-7: EXAMPLE OF FULL-BRIDGE APPLICATION 16.4.5.1 Direction Change in Full-Bridge Mode In the Full-Bridge Output mode, the P1M1 bit in the CCP1CON register allows the user to control the forward/reverse direction. When the application firmware changes this direction control bit, the module will assume the new direction on the next PWM cycle. Just before the end of the current PWM period, the modulated outputs (P1B and P1D) are placed in their inactive state, while the unmodulated outputs (P1A and P1C) are switched to drive in the opposite direction. This occurs in a time interval of (4 TOSC * (Timer2 Prescale Value) before the next PWM period begins. The Timer2 prescaler will be either 1, 4 or 16, depending on the value of the T2CKPS1:T2CKPS0 bits (T2CON<1:0>). During the interval from the switch of the unmodulated outputs to the beginning of the next period, the modulated outputs (P1B and P1D) remain inactive. This relationship is shown in Figure 16-8. Note that in the Full-Bridge Output mode, the ECCP module does not provide any dead-band delay. In general, since only one output is modulated at all times, dead-band delay is not required. However, there is a situation where a dead-band delay might be required. This situation occurs when both of the following conditions are true: 1. The direction of the PWM output changes when the duty cycle of the output is at or near 100%. 2. The turn-off time of the power switch, including the power device and driver circuit, is greater than the turn-on time. Figure 16-9 shows an example where the PWM direction changes from forward to reverse at a near 100% duty cycle. At time t1, the outputs, P1A and P1D, become inactive, while output P1C becomes active. In this example, since the turn-off time of the power devices is longer than the turn-on time, a shoot-through current may flow through power devices, QC and QD, (see Figure 16-7) for the duration of ‘t’. The same phenomenon will occur to power devices, QA and QB, for PWM direction change from reverse to forward. If changing PWM direction at high duty cycle is required for an application, one of the following requirements must be met: 1. Reduce PWM for a PWM period before changing directions. 2. Use switch drivers that can drive the switches off faster than they can drive them on. Other options to prevent shoot-through current may exist. P1A P1C FET Driver FET Driver V+ VLoad FET Driver FET Driver P1B P1D QA QB QD PIC18FX455/X550 QC © 2009 Microchip Technology Inc. DS39632E-page 159 PIC18F2455/2550/4455/4550 FIGURE 16-8: PWM DIRECTION CHANGE FIGURE 16-9: PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE DC Period(1) SIGNAL Note 1: The direction bit in the CCP1 Control register (CCP1CON<7>) is written any time during the PWM cycle. 2: When changing directions, the P1A and P1C signals switch before the end of the current PWM cycle at intervals of 4 TOSC, 16 TOSC or 64 TOSC, depending on the Timer2 prescaler value. The modulated P1B and P1D signals are inactive at this time. Period (Note 2) P1A (Active-High) P1B (Active-High) P1C (Active-High) P1D (Active-High) DC Forward Period Reverse Period P1A(1) tON (2) tOFF (3) t = tOFF – tON (2, 3) P1B(1) P1C(1) P1D(1) External Switch D(1) Potential Shoot-Through Current(1) Note 1: All signals are shown as active-high. 2: tON is the turn-on delay of power switch QC and its driver. 3: tOFF is the turn-off delay of power switch QD and its driver. External Switch C(1) t1 DC DC PIC18F2455/2550/4455/4550 DS39632E-page 160 © 2009 Microchip Technology Inc. 16.4.6 PROGRAMMABLE DEAD-BAND DELAY In half-bridge applications where all power switches are modulated at the PWM frequency at all times, the power switches normally require more time to turn off than to turn on. If both the upper and lower power switches are switched at the same time (one turned on and the other turned off), both switches may be on for a short period of time until one switch completely turns off. During this brief interval, a very high current (shoot-through current) may flow through both power switches, shorting the bridge supply. To avoid this potentially destructive shoot-through current from flowing during switching, turning on either of the power switches is normally delayed to allow the other switch to completely turn off. In the Half-Bridge Output mode, a digitally programmable dead-band delay is available to avoid shoot-through current from destroying the bridge power switches. The delay occurs at the signal transition from the non-active state to the active state. See Figure 16-4 for illustration. Bits PDC6:PDC0 of the ECCP1DEL register (Register 16-2) set the delay period in terms of microcontroller instruction cycles (TCY or 4 TOSC). These bits are not available on 28-pin devices, as the standard CCP module does not support half-bridge operation. 16.4.7 ENHANCED PWM AUTO-SHUTDOWN When ECCP is programmed for any of the Enhanced PWM modes, the active output pins may be configured for auto-shutdown. Auto-shutdown immediately places the Enhanced PWM output pins into a defined shutdown state when a shutdown event occurs. A shutdown event can be caused by either of the comparator modules, a low level on the RB0/AN12/INT0/FLT0/SDI/SDA pin, or any combination of these three sources. The comparators may be used to monitor a voltage input proportional to a current being monitored in the bridge circuit. If the voltage exceeds a threshold, the comparator switches state and triggers a shutdown. Alternatively, a digital signal on the INT0 pin can also trigger a shutdown. The auto-shutdown feature can be disabled by not selecting any auto-shutdown sources. The auto-shutdown sources to be used are selected using the ECCPAS2:ECCPAS0 bits (bits<6:4> of the ECCP1AS register). When a shutdown occurs, the output pins are asynchronously placed in their shutdown states, specified by the PSSAC1:PSSAC0 and PSSBD1:PSSBD0 bits (ECCP1AS3:ECCP1AS0). Each pin pair (P1A/P1C and P1B/P1D) may be set to drive high, drive low or be tri-stated (not driving). The ECCPASE bit (ECCP1AS<7>) is also set to hold the Enhanced PWM outputs in their shutdown states. The ECCPASE bit is set by hardware when a shutdown event occurs. If automatic restarts are not enabled, the ECCPASE bit is cleared by firmware when the cause of the shutdown clears. If automatic restarts are enabled, the ECCPASE bit is automatically cleared when the cause of the auto-shutdown has cleared. If the ECCPASE bit is set when a PWM period begins, the PWM outputs remain in their shutdown state for that entire PWM period. When the ECCPASE bit is cleared, the PWM outputs will return to normal operation at the beginning of the next PWM period. Note: Programmable dead-band delay is not implemented in 28-pin devices with standard CCP modules. Note: Writing to the ECCPASE bit is disabled while a shutdown condition is active. REGISTER 16-2: ECCP1DEL: PWM DEAD-BAND DELAY REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 PRSEN PDC6(1) PDC5(1) PDC4(1) PDC3(1) PDC2(1) PDC1(1) PDC0(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 PRSEN: PWM Restart Enable bit 1 = Upon auto-shutdown, the ECCPASE bit clears automatically once the shutdown event goes away; the PWM restarts automatically 0 = Upon auto-shutdown, ECCPASE must be cleared in software to restart the PWM bit 6-0 PDC6:PDC0: PWM Delay Count bits(1) Delay time, in number of FOSC/4 (4 * TOSC) cycles, between the scheduled and actual time for a PWM signal to transition to active. Note 1: Reserved on 28-pin devices; maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 161 PIC18F2455/2550/4455/4550 REGISTER 16-3: ECCP1AS: ENHANCED CAPTURE/COMPARE/PWM AUTO-SHUTDOWN CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(1) PSSBD0(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 ECCPASE: ECCP Auto-Shutdown Event Status bit 1 = A shutdown event has occurred; ECCP outputs are in shutdown state 0 = ECCP outputs are operating bit 6-4 ECCPAS2:ECCPAS0: ECCP Auto-Shutdown Source Select bits 111 = FLT0 or Comparator 1 or Comparator 2 110 = FLT0 or Comparator 2 101 = FLT0 or Comparator 1 100 = FLT0 011 = Either Comparator 1 or 2 010 = Comparator 2 output 001 = Comparator 1 output 000 = Auto-shutdown is disabled bit 3-2 PSSAC1:PSSAC0: Pins A and C Shutdown State Control bits 1x = Pins A and C tri-state (40/44-pin devices) 01 = Drive Pins A and C to ‘1’ 00 = Drive Pins A and C to ‘0’ bit 1-0 PSSBD1:PSSBD0: Pins B and D Shutdown State Control bits(1) 1x = Pins B and D tri-state 01 = Drive Pins B and D to ‘1’ 00 = Drive Pins B and D to ‘0’ Note 1: Reserved on 28-pin devices; maintain these bits clear. PIC18F2455/2550/4455/4550 DS39632E-page 162 © 2009 Microchip Technology Inc. 16.4.7.1 Auto-Shutdown and Auto-Restart The auto-shutdown feature can be configured to allow automatic restarts of the module following a shutdown event. This is enabled by setting the PRSEN bit of the ECCP1DEL register (ECCP1DEL<7>). In Shutdown mode with PRSEN = 1 (Figure 16-10), the ECCPASE bit will remain set for as long as the cause of the shutdown continues. When the shutdown condition clears, the ECCP1ASE bit is cleared. If PRSEN = 0 (Figure 16-11), once a shutdown condition occurs, the ECCPASE bit will remain set until it is cleared by firmware. Once ECCPASE is cleared, the Enhanced PWM will resume at the beginning of the next PWM period. Independent of the PRSEN bit setting, if the auto-shutdown source is one of the comparators, the shutdown condition is a level. The ECCPASE bit cannot be cleared as long as the cause of the shutdown persists. The Auto-Shutdown mode can be forced by writing a ‘1’ to the ECCPASE bit. 16.4.8 START-UP CONSIDERATIONS When the ECCP module is used in the PWM mode, the application hardware must use the proper external pull-up and/or pull-down resistors on the PWM output pins. When the microcontroller is released from Reset, all of the I/O pins are in the high-impedance state. The external circuits must keep the power switch devices in the OFF state until the microcontroller drives the I/O pins with the proper signal levels or activates the PWM output(s). The CCP1M1:CCP1M0 bits (CCP1CON<1:0>) allow the user to choose whether the PWM output signals are active-high or active-low for each pair of PWM output pins (P1A/P1C and P1B/P1D). The PWM output polarities must be selected before the PWM pins are configured as outputs. Changing the polarity configuration while the PWM pins are configured as outputs is not recommended, since it may result in damage to the application circuits. The P1A, P1B, P1C and P1D output latches may not be in the proper states when the PWM module is initialized. Enabling the PWM pins for output at the same time as the ECCP module may cause damage to the application circuit. The ECCP module must be enabled in the proper output mode and complete a full PWM cycle before configuring the PWM pins as outputs. The completion of a full PWM cycle is indicated by the TMR2IF bit being set as the second PWM period begins. FIGURE 16-10: PWM AUTO-SHUTDOWN (PRSEN = 1, AUTO-RESTART ENABLED) FIGURE 16-11: PWM AUTO-SHUTDOWN (PRSEN = 0, AUTO-RESTART DISABLED) Note: Writing to the ECCPASE bit is disabled while a shutdown condition is active. Shutdown PWM ECCPASE bit Activity Event PWM Period PWM Period PWM Period Duty Cycle Dead Time Duty Cycle Dead Time Duty Cycle Dead Time Shutdown PWM ECCPASE bit Activity Event PWM Period PWM Period PWM Period ECCPASE Cleared by Firmware Duty Cycle Dead Time Duty Cycle Dead Time Dead Time Duty Cycle © 2009 Microchip Technology Inc. DS39632E-page 163 PIC18F2455/2550/4455/4550 16.4.9 SETUP FOR PWM OPERATION The following steps should be taken when configuring the ECCP module for PWM operation: 1. Configure the PWM pins, P1A and P1B (and P1C and P1D, if used), as inputs by setting the corresponding TRIS bits. 2. Set the PWM period by loading the PR2 register. 3. If auto-shutdown is required, do the following: • Disable auto-shutdown (ECCPASE = 0) • Configure source (FLT0, Comparator 1 or Comparator 2) • Wait for non-shutdown condition 4. Configure the ECCP module for the desired PWM mode and configuration by loading the CCP1CON register with the appropriate values: • Select one of the available output configurations and direction with the P1M1:P1M0 bits. • Select the polarities of the PWM output signals with the CCP1M3:CCP1M0 bits. 5. Set the PWM duty cycle by loading the CCPR1L register and CCP1CON<5:4> bits. 6. For Half-Bridge Output mode, set the dead-band delay by loading ECCP1DEL<6:0> with the appropriate value. 7. If auto-shutdown operation is required, load the ECCP1AS register: • Select the auto-shutdown sources using the ECCPAS2:ECCPAS0 bits. • Select the shutdown states of the PWM output pins using the PSSAC1:PSSAC0 and PSSBD1:PSSBD0 bits. • Set the ECCPASE bit (ECCP1AS<7>). • Configure the comparators using the CMCON register. • Configure the comparator inputs as analog inputs. 8. If auto-restart operation is required, set the PRSEN bit (ECCP1DEL<7>). 9. Configure and start TMR2: • Clear the TMR2 interrupt flag bit by clearing the TMR2IF bit (PIR1<1>). • Set the TMR2 prescale value by loading the T2CKPS bits (T2CON<1:0>). • Enable Timer2 by setting the TMR2ON bit (T2CON<2>). 10. Enable PWM outputs after a new PWM cycle has started: • Wait until TMRx overflows (TMRxIF bit is set). • Enable the CCP1/P1A, P1B, P1C and/or P1D pin outputs by clearing the respective TRIS bits. • Clear the ECCPASE bit (ECCP1AS<7>). 16.4.10 OPERATION IN POWER-MANAGED MODES In Sleep mode, all clock sources are disabled. Timer2 will not increment and the state of the module will not change. If the ECCP pin is driving a value, it will continue to drive that value. When the device wakes up, it will continue from this state. If Two-Speed Start-ups are enabled, the initial start-up frequency from INTOSC and the postscaler may not be stable immediately. In PRI_IDLE mode, the primary clock will continue to clock the ECCP module without change. In all other power-managed modes, the selected power-managed mode clock will clock Timer2. Other power-managed mode clocks will most likely be different than the primary clock frequency. 16.4.10.1 Operation with Fail-Safe Clock Monitor If the Fail-Safe Clock Monitor is enabled, a clock failure will force the device into the power-managed RC_RUN mode and the OSCFIF bit (PIR2<7>) will be set. The ECCP will then be clocked from the internal oscillator clock source, which may have a different clock frequency than the primary clock. See the previous section for additional details. 16.4.11 EFFECTS OF A RESET Both Power-on Reset and subsequent Resets will force all ports to Input mode and the CCP registers to their Reset states. This forces the Enhanced CCP module to reset to a state compatible with the standard CCP module. PIC18F2455/2550/4455/4550 DS39632E-page 164 © 2009 Microchip Technology Inc. TABLE 16-3: REGISTERS ASSOCIATED WITH ECCP MODULE AND TIMER1 TO TIMER3 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 RCON IPEN SBOREN(1) — RI TO PD POR BOR 54 IPR1 SPPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 PIR1 SPPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 TRISD(2) TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 56 TMR1L Timer1 Register Low Byte 54 TMR1H Timer1 Register High Byte 54 T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 54 TMR2 Timer2 Module Register 54 T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 54 PR2 Timer2 Period Register 54 TMR3L Timer3 Register Low Byte 55 TMR3H Timer3 Register High Byte 55 T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 55 CCPR1L Capture/Compare/PWM Register 1 (LSB) 55 CCPR1H Capture/Compare/PWM Register 1 (MSB) 55 CCP1CON P1M1(2) P1M0(2) DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 55 ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1(2) PSSBD0(2) 55 ECCP1DEL PRSEN PDC6(2) PDC5(2) PDC4(2) PDC3(2) PDC2(2) PDC1(2) PDC0(2) 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during ECCP operation. Note 1: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. 2: These bits or registers are unimplemented in 28-pin devices; always maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 165 PIC18F2455/2550/4455/4550 17.0 UNIVERSAL SERIAL BUS (USB) This section describes the details of the USB peripheral. Because of the very specific nature of the module, knowledge of USB is expected. Some high-level USB information is provided in Section 17.10 “Overview of USB” only for application design reference. Designers are encouraged to refer to the official specification published by the USB Implementers Forum (USB-IF) for the latest information. USB specification Revision 2.0 is the most current specification at the time of publication of this document. 17.1 Overview of the USB Peripheral The PIC18FX455/X550 device family contains a full-speed and low-speed compatible USB Serial Interface Engine (SIE) that allows fast communication between any USB host and the PIC® microcontroller. The SIE can be interfaced directly to the USB, utilizing the internal transceiver, or it can be connected through an external transceiver. An internal 3.3V regulator is also available to power the internal transceiver in 5V applications. Some special hardware features have been included to improve performance. Dual port memory in the device’s data memory space (USB RAM) has been supplied to share direct memory access between the microcontroller core and the SIE. Buffer descriptors are also provided, allowing users to freely program endpoint memory usage within the USB RAM space. A Streaming Parallel Port has been provided to support the uninterrupted transfer of large volumes of data, such as isochronous data, to external memory buffers. Figure 17-1 presents a general overview of the USB peripheral and its features. FIGURE 17-1: USB PERIPHERAL AND OPTIONS UOE(1) 1 Kbyte USB RAM USB SIE USB Control and VM(1) VP(1) RCV(1) VMO(1) VPO(1) Transceiver External Transceiver P P EN 3.3V Regulator D+ DInternal Pull-ups UOE VUSB External 3.3V Supply(3) FSEN UPUEN UTRDIS USB Clock from the Oscillator Module VREGEN Optional External Pull-ups(2) (Full (Low PIC18FX455/X550 Family SPP7:SPP0 USB Bus USB Bus FS Speed) Speed) Note 1: This signal is only available if the internal transceiver is disabled (UTRDIS = 1). 2: The internal pull-up resistors should be disabled (UPUEN = 0) if external pull-up resistors are used. 3: Do not enable the internal regulator when using an external 3.3V supply. Configuration CK1SPP CK2SPP CSSPP OESPP PIC18F2455/2550/4455/4550 DS39632E-page 166 © 2009 Microchip Technology Inc. 17.2 USB Status and Control The operation of the USB module is configured and managed through three control registers. In addition, a total of 22 registers are used to manage the actual USB transactions. The registers are: • USB Control register (UCON) • USB Configuration register (UCFG) • USB Transfer Status register (USTAT) • USB Device Address register (UADDR) • Frame Number registers (UFRMH:UFRML) • Endpoint Enable registers 0 through 15 (UEPn) 17.2.1 USB CONTROL REGISTER (UCON) The USB Control register (Register 17-1) contains bits needed to control the module behavior during transfers. The register contains bits that control the following: • Main USB Peripheral Enable • Ping-Pong Buffer Pointer Reset • Control of the Suspend mode • Packet Transfer Disable In addition, the USB Control register contains a status bit, SE0 (UCON<5>), which is used to indicate the occurrence of a single-ended zero on the bus. When the USB module is enabled, this bit should be monitored to determine whether the differential data lines have come out of a single-ended zero condition. This helps to differentiate the initial power-up state from the USB Reset signal. The overall operation of the USB module is controlled by the USBEN bit (UCON<3>). Setting this bit activates the module and resets all of the PPBI bits in the Buffer Descriptor Table to ‘0’. This bit also activates the on-chip voltage regulator (if the VREGEN Configuration bit is set) and connects internal pull-up resistors, if they are enabled. Thus, this bit can be used as a soft attach/detach to the USB. Although all status and control bits are ignored when this bit is clear, the module needs to be fully preconfigured prior to setting this bit. Note: When disabling the USB module, make sure the SUSPND bit (UCON<1>) is clear prior to clearing the USBEN bit. Clearing the USBEN bit when the module is in the suspended state may prevent the module from fully powering down. REGISTER 17-1: UCON: USB CONTROL REGISTER U-0 R/W-0 R-x R/C-0 R/W-0 R/W-0 R/W-0 U-0 — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — bit 7 bit 0 Legend: C = Clearable bit R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 Unimplemented: Read as ‘0’ bit 6 PPBRST: Ping-Pong Buffers Reset bit 1 = Reset all Ping-Pong Buffer Pointers to the Even Buffer Descriptor (BD) banks 0 = Ping-Pong Buffer Pointers not being reset bit 5 SE0: Live Single-Ended Zero Flag bit 1 = Single-ended zero active on the USB bus 0 = No single-ended zero detected bit 4 PKTDIS: Packet Transfer Disable bit 1 = SIE token and packet processing disabled, automatically set when a SETUP token is received 0 = SIE token and packet processing enabled bit 3 USBEN: USB Module Enable bit 1 = USB module and supporting circuitry enabled (device attached) 0 = USB module and supporting circuitry disabled (device detached) bit 2 RESUME: Resume Signaling Enable bit 1 = Resume signaling activated 0 = Resume signaling disabled bit 1 SUSPND: Suspend USB bit 1 = USB module and supporting circuitry in Power Conserve mode, SIE clock inactive 0 = USB module and supporting circuitry in normal operation, SIE clock clocked at the configured rate bit 0 Unimplemented: Read as ‘0’ © 2009 Microchip Technology Inc. DS39632E-page 167 PIC18F2455/2550/4455/4550 The PPBRST bit (UCON<6>) controls the Reset status when Double-Buffering mode (ping-pong buffering) is used. When the PPBRST bit is set, all Ping-Pong Buffer Pointers are set to the Even buffers. PPBRST has to be cleared by firmware. This bit is ignored in buffering modes not using ping-pong buffering. The PKTDIS bit (UCON<4>) is a flag indicating that the SIE has disabled packet transmission and reception. This bit is set by the SIE when a SETUP token is received to allow setup processing. This bit cannot be set by the microcontroller, only cleared; clearing it allows the SIE to continue transmission and/or reception. Any pending events within the Buffer Descriptor Table will still be available, indicated within the USTAT register’s FIFO buffer. The RESUME bit (UCON<2>) allows the peripheral to perform a remote wake-up by executing Resume signaling. To generate a valid remote wake-up, firmware must set RESUME for 10 ms and then clear the bit. For more information on Resume signaling, see Sections 7.1.7.5, 11.4.4 and 11.9 in the USB 2.0 specification. The SUSPND bit (UCON<1>) places the module and supporting circuitry (i.e., voltage regulator) in a low-power mode. The input clock to the SIE is also disabled. This bit should be set by the software in response to an IDLEIF interrupt. It should be reset by the microcontroller firmware after an ACTVIF interrupt is observed. When this bit is active, the device remains attached to the bus but the transceiver outputs remain Idle. The voltage on the VUSB pin may vary depending on the value of this bit. Setting this bit before a IDLEIF request will result in unpredictable bus behavior. 17.2.2 USB CONFIGURATION REGISTER (UCFG) Prior to communicating over USB, the module’s associated internal and/or external hardware must be configured. Most of the configuration is performed with the UCFG register (Register 17-2). The separate USB voltage regulator (see Section 17.2.2.8 “Internal Regulator”) is controlled through the Configuration registers. The UFCG register contains most of the bits that control the system level behavior of the USB module. These include: • Bus Speed (full speed versus low speed) • On-Chip Pull-up Resistor Enable • On-Chip Transceiver Enable • Ping-Pong Buffer Usage The UCFG register also contains two bits which aid in module testing, debugging and USB certifications. These bits control output enable state monitoring and eye pattern generation. 17.2.2.1 Internal Transceiver The USB peripheral has a built-in, USB 2.0, full-speed and low-speed compliant transceiver, internally connected to the SIE. This feature is useful for low-cost single chip applications. The UTRDIS bit (UCFG<3>) controls the transceiver; it is enabled by default (UTRDIS = 0). The FSEN bit (UCFG<2>) controls the transceiver speed; setting the bit enables full-speed operation. The on-chip USB pull-up resistors are controlled by the UPUEN bit (UCFG<4>). They can only be selected when the on-chip transceiver is enabled. The USB specification requires 3.3V operation for communications; however, the rest of the chip may be running at a higher voltage. Thus, the transceiver is supplied power from a separate source, VUSB. 17.2.2.2 External Transceiver This module provides support for use with an off-chip transceiver. The off-chip transceiver is intended for applications where physical conditions dictate the location of the transceiver to be away from the SIE. External transceiver operation is enabled by setting the UTRDIS bit. FIGURE 17-2: TYPICAL EXTERNAL TRANSCEIVER WITH ISOLATION Note: While in Suspend mode, a typical bus powered USB device is limited to 2.5 mA of current. Care should be taken to assure minimum current draw when the device enters Suspend mode. Note: The USB speed, transceiver and pull-up should only be configured during the module setup phase. It is not recommended to switch these settings while the module is enabled. PIC® Microcontroller Transceiver VPO UOE Note: The above setting shows a simplified schematic for a full-speed configuration using an external transceiver with isolation. VP RCV VMO VM D+ DIsolation 1.5 kΩ 3.3V Derived from USB VUSB VDD VDD Isolated from USB PIC18F2455/2550/4455/4550 DS39632E-page 168 © 2009 Microchip Technology Inc. There are 6 signals from the module to communicate with and control an external transceiver: • VM: Input from the single-ended D- line • VP: Input from the single-ended D+ line • RCV: Input from the differential receiver • VMO: Output to the differential line driver • VPO: Output to the differential line driver • UOE: Output enable The VPO and VMO signals are outputs from the SIE to the external transceiver. The RCV signal is the output from the external transceiver to the SIE; it represents the differential signals from the serial bus translated into a single pulse train. The VM and VP signals are used to report conditions on the serial bus to the SIE that can’t be captured with the RCV signal. The combinations of states of these signals and their interpretation are listed in Table 17-1 and Table 17-2. REGISTER 17-2: UCFG: USB CONFIGURATION REGISTER R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 UTEYE UOEMON(1) — UPUEN(2,3) UTRDIS(2) FSEN(2) PPB1 PPB0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 UTEYE: USB Eye Pattern Test Enable bit 1 = Eye pattern test enabled 0 = Eye pattern test disabled bit 6 UOEMON: USB OE Monitor Enable bit(1) 1 = UOE signal active; it indicates intervals during which the D+/D- lines are driving 0 = UOE signal inactive bit 5 Unimplemented: Read as ‘0’ bit 4 UPUEN: USB On-Chip Pull-up Enable bit(2,3) 1 = On-chip pull-up enabled (pull-up on D+ with FSEN = 1 or D- with FSEN = 0) 0 = On-chip pull-up disabled bit 3 UTRDIS: On-Chip Transceiver Disable bit(2) 1 = On-chip transceiver disabled; digital transceiver interface enabled 0 = On-chip transceiver active bit 2 FSEN: Full-Speed Enable bit(2) 1 = Full-speed device: controls transceiver edge rates; requires input clock at 48 MHz 0 = Low-speed device: controls transceiver edge rates; requires input clock at 6 MHz bit 1-0 PPB1:PPB0: Ping-Pong Buffers Configuration bits 11 = Even/Odd ping-pong buffers enabled for Endpoints 1 to 15 10 = Even/Odd ping-pong buffers enabled for all endpoints 01 = Even/Odd ping-pong buffer enabled for OUT Endpoint 0 00 = Even/Odd ping-pong buffers disabled Note 1: If UTRDIS is set, the UOE signal will be active independent of the UOEMON bit setting. 2: The UPUEN, UTRDIS and FSEN bits should never be changed while the USB module is enabled. These values must be preconfigured prior to enabling the module. 3: This bit is only valid when the on-chip transceiver is active (UTRDIS = 0); otherwise, it is ignored. © 2009 Microchip Technology Inc. DS39632E-page 169 PIC18F2455/2550/4455/4550 TABLE 17-1: DIFFERENTIAL OUTPUTS TO TRANSCEIVER TABLE 17-2: SINGLE-ENDED INPUTS FROM TRANSCEIVER The UOE signal toggles the state of the external transceiver. This line is pulled low by the device to enable the transmission of data from the SIE to an external device. 17.2.2.3 Internal Pull-up Resistors The PIC18FX455/X550 devices have built-in pull-up resistors designed to meet the requirements for low-speed and full-speed USB. The UPUEN bit (UCFG<4>) enables the internal pull-ups. Figure 17-1 shows the pull-ups and their control. 17.2.2.4 External Pull-up Resistors External pull-up may also be used if the internal resistors are not used. The VUSB pin may be used to pull up D+ or D-. The pull-up resistor must be 1.5 kΩ (±5%) as required by the USB specifications. Figure 17-3 shows an example. FIGURE 17-3: EXTERNAL CIRCUITRY 17.2.2.5 Ping-Pong Buffer Configuration The usage of ping-pong buffers is configured using the PPB1:PPB0 bits. Refer to Section 17.4.4 “Ping-Pong Buffering” for a complete explanation of the ping-pong buffers. 17.2.2.6 USB Output Enable Monitor The USB OE monitor provides indication as to whether the SIE is listening to the bus or actively driving the bus. This is enabled by default when using an external transceiver or when UCFG<6> = 1. The USB OE monitoring is useful for initial system debugging, as well as scope triggering during eye pattern generation tests. 17.2.2.7 Eye Pattern Test Enable An automatic eye pattern test can be generated by the module when the UCFG<7> bit is set. The eye pattern output will be observable based on module settings, meaning that the user is first responsible for configuring the SIE clock settings, pull-up resistor and Transceiver mode. In addition, the module has to be enabled. Once UTEYE is set, the module emulates a switch from a receive to transmit state and will start transmitting a J-K-J-K bit sequence (K-J-K-J for full speed). The sequence will be repeated indefinitely while the Eye Pattern Test mode is enabled. Note that this bit should never be set while the module is connected to an actual USB system. This test mode is intended for board verification to aid with USB certification tests. It is intended to show a system developer the noise integrity of the USB signals which can be affected by board traces, impedance mismatches and proximity to other system components. It does not properly test the transition from a receive to a transmit state. Although the eye pattern is not meant to replace the more complex USB certification test, it should aid during first order system debugging. VPO VMO Bus State 0 0 Single-Ended Zero 0 1 Differential ‘0’ 1 0 Differential ‘1’ 1 1 Illegal Condition VP VM Bus State 0 0 Single-Ended Zero 0 1 Low Speed 1 0 High Speed 1 1 Error PIC® Microcontroller Host Controller/HUB VUSB D+ DNote: The above setting shows a typical connection for a full-speed configuration using an on-chip regulator and an external pull-up resistor. 1.5 kΩ PIC18F2455/2550/4455/4550 DS39632E-page 170 © 2009 Microchip Technology Inc. 17.2.2.8 Internal Regulator The PIC18FX455/X550 devices have a built-in 3.3V regulator to provide power to the internal transceiver and provide a source for the internal/external pull-ups. An external 220 nF (±20%) capacitor is required for stability. The regulator can be enabled or disabled through the VREGEN Configuration bit. When enabled, the voltage is visible on pin VUSB whenever the USBEN bit is also set. When the regulator is disabled (VREGEN = 0), a 3.3V source must be provided through the VUSB pin for the internal transceiver. 17.2.3 USB STATUS REGISTER (USTAT) The USB Status register reports the transaction status within the SIE. When the SIE issues a USB transfer complete interrupt, USTAT should be read to determine the status of the transfer. USTAT contains the transfer endpoint number, direction and Ping-Pong Buffer Pointer value (if used). The USTAT register is actually a read window into a four-byte status FIFO, maintained by the SIE. It allows the microcontroller to process one transfer while the SIE processes additional endpoints (Figure 17-4). When the SIE completes using a buffer for reading or writing data, it updates the USTAT register. If another USB transfer is performed before a transaction complete interrupt is serviced, the SIE will store the status of the next transfer into the status FIFO. Clearing the transfer complete flag bit, TRNIF, causes the SIE to advance the FIFO. If the next data in the FIFO holding register is valid, the SIE will reassert the interrupt within 5 TCY of clearing TRNIF. If no additional data is present, TRNIF will remain clear; USTAT data will no longer be reliable. FIGURE 17-4: USTAT FIFO Note: The drive from VUSB is sufficient to only drive an external pull-up in addition to the internal transceiver. Note 1: Do not enable the internal regulator if an external regulator is connected to VUSB. 2: VDD must be equal to or greater than VUSB at all times, even with the regulator disabled. Note: The data in the USB Status register is valid only when the TRNIF interrupt flag is asserted. Note: If an endpoint request is received while the USTAT FIFO is full, the SIE will automatically issue a NAK back to the host. Data Bus USTAT from SIE 4-byte FIFO for USTAT Clearing TRNIF Advances FIFO © 2009 Microchip Technology Inc. DS39632E-page 171 PIC18F2455/2550/4455/4550 REGISTER 17-3: USTAT: USB STATUS REGISTER U-0 R-x R-x R-x R-x R-x R-x U-0 — ENDP3 ENDP2 ENDP1 ENDP0 DIR PPBI(1) — bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 Unimplemented: Read as ‘0’ bit 6-3 ENDP3:ENDP0: Encoded Number of Last Endpoint Activity bits (represents the number of the BDT updated by the last USB transfer) 1111 = Endpoint 15 1110 = Endpoint 14 .... 0001 = Endpoint 1 0000 = Endpoint 0 bit 2 DIR: Last BD Direction Indicator bit 1 = The last transaction was an IN token 0 = The last transaction was an OUT or SETUP token bit 1 PPBI: Ping-Pong BD Pointer Indicator bit(1) 1 = The last transaction was to the Odd BD bank 0 = The last transaction was to the Even BD bank bit 0 Unimplemented: Read as ‘0’ Note 1: This bit is only valid for endpoints with available Even and Odd BD registers. PIC18F2455/2550/4455/4550 DS39632E-page 172 © 2009 Microchip Technology Inc. 17.2.4 USB ENDPOINT CONTROL Each of the 16 possible bidirectional endpoints has its own independent control register, UEPn (where ‘n’ represents the endpoint number). Each register has an identical complement of control bits. The prototype is shown in Register 17-4. The EPHSHK bit (UEPn<4>) controls handshaking for the endpoint; setting this bit enables USB handshaking. Typically, this bit is always set except when using isochronous endpoints. The EPCONDIS bit (UEPn<3>) is used to enable or disable USB control operations (SETUP) through the endpoint. Clearing this bit enables SETUP transactions. Note that the corresponding EPINEN and EPOUTEN bits must be set to enable IN and OUT transactions. For Endpoint 0, this bit should always be cleared since the USB specifications identify Endpoint 0 as the default control endpoint. The EPOUTEN bit (UEPn<2>) is used to enable or disable USB OUT transactions from the host. Setting this bit enables OUT transactions. Similarly, the EPINEN bit (UEPn<1>) enables or disables USB IN transactions from the host. The EPSTALL bit (UEPn<0>) is used to indicate a STALL condition for the endpoint. If a STALL is issued on a particular endpoint, the EPSTALL bit for that endpoint pair will be set by the SIE. This bit remains set until it is cleared through firmware, or until the SIE is reset. REGISTER 17-4: UEPn: USB ENDPOINT n CONTROL REGISTER (UEP0 THROUGH UEP15) U-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-5 Unimplemented: Read as ‘0’ bit 4 EPHSHK: Endpoint Handshake Enable bit 1 = Endpoint handshake enabled 0 = Endpoint handshake disabled (typically used for isochronous endpoints) bit 3 EPCONDIS: Bidirectional Endpoint Control bit If EPOUTEN = 1 and EPINEN = 1: 1 = Disable Endpoint n from control transfers; only IN and OUT transfers allowed 0 = Enable Endpoint n for control (SETUP) transfers; IN and OUT transfers also allowed bit 2 EPOUTEN: Endpoint Output Enable bit 1 = Endpoint n output enabled 0 = Endpoint n output disabled bit 1 EPINEN: Endpoint Input Enable bit 1 = Endpoint n input enabled 0 = Endpoint n input disabled bit 0 EPSTALL: Endpoint Stall Indicator bit 1 = Endpoint n has issued one or more STALL packets 0 = Endpoint n has not issued any STALL packets © 2009 Microchip Technology Inc. DS39632E-page 173 PIC18F2455/2550/4455/4550 17.2.5 USB ADDRESS REGISTER (UADDR) The USB Address register contains the unique USB address that the peripheral will decode when active. UADDR is reset to 00h when a USB Reset is received, indicated by URSTIF, or when a Reset is received from the microcontroller. The USB address must be written by the microcontroller during the USB setup phase (enumeration) as part of the Microchip USB firmware support. 17.2.6 USB FRAME NUMBER REGISTERS (UFRMH:UFRML) The Frame Number registers contain the 11-bit frame number. The low-order byte is contained in UFRML, while the three high-order bits are contained in UFRMH. The register pair is updated with the current frame number whenever a SOF token is received. For the microcontroller, these registers are read-only. The Frame Number register is primarily used for isochronous transfers. 17.3 USB RAM USB data moves between the microcontroller core and the SIE through a memory space known as the USB RAM. This is a special dual port memory that is mapped into the normal data memory space in Banks 4 through 7 (400h to 7FFh) for a total of 1 Kbyte (Figure 17-5). Bank 4 (400h through 4FFh) is used specifically for endpoint buffer control, while Banks 5 through 7 are available for USB data. Depending on the type of buffering being used, all but 8 bytes of Bank 4 may also be available for use as USB buffer space. Although USB RAM is available to the microcontroller as data memory, the sections that are being accessed by the SIE should not be accessed by the microcontroller. A semaphore mechanism is used to determine the access to a particular buffer at any given time. This is discussed in Section 17.4.1.1 “Buffer Ownership”. FIGURE 17-5: IMPLEMENTATION OF USB RAM IN DATA MEMORY SPACE 400h 4FFh 7FFh 500h USB Data or Buffer Descriptors, USB Data or User Data User Data User Data Unused SFRs 3FFh 000h F60h FFFh Banks 0 Banks 4 Bank15 (USB RAM) F00h Banks 8 800h to 14 to 3 to 7 PIC18F2455/2550/4455/4550 DS39632E-page 174 © 2009 Microchip Technology Inc. 17.4 Buffer Descriptors and the Buffer Descriptor Table The registers in Bank 4 are used specifically for endpoint buffer control in a structure known as the Buffer Descriptor Table (BDT). This provides a flexible method for users to construct and control endpoint buffers of various lengths and configuration. The BDT is composed of Buffer Descriptors (BD) which are used to define and control the actual buffers in the USB RAM space. Each BD, in turn, consists of four registers, where n represents one of the 64 possible BDs (range of 0 to 63): • BDnSTAT: BD Status register • BDnCNT: BD Byte Count register • BDnADRL: BD Address Low register • BDnADRH: BD Address High register BDs always occur as a four-byte block in the sequence, BDnSTAT:BDnCNT:BDnADRL:BDnADRH. The address of BDnSTAT is always an offset of (4n – 1) (in hexadecimal) from 400h, with n being the buffer descriptor number. Depending on the buffering configuration used (Section 17.4.4 “Ping-Pong Buffering”), there are up to 32, 33 or 64 sets of buffer descriptors. At a minimum, the BDT must be at least 8 bytes long. This is because the USB specification mandates that every device must have Endpoint 0 with both input and output for initial setup. Depending on the endpoint and buffering configuration, the BDT can be as long as 256 bytes. Although they can be thought of as Special Function Registers, the Buffer Descriptor Status and Address registers are not hardware mapped, as conventional microcontroller SFRs in Bank 15 are. If the endpoint corresponding to a particular BD is not enabled, its registers are not used. Instead of appearing as unimplemented addresses, however, they appear as available RAM. Only when an endpoint is enabled by setting the UEPn<1> bit does the memory at those addresses become functional as BD registers. As with any address in the data memory space, the BD registers have an indeterminate value on any device Reset. An example of a BD for a 64-byte buffer, starting at 500h, is shown in Figure 17-6. A particular set of BD registers is only valid if the corresponding endpoint has been enabled using the UEPn register. All BD registers are available in USB RAM. The BD for each endpoint should be set up prior to enabling the endpoint. 17.4.1 BD STATUS AND CONFIGURATION Buffer descriptors not only define the size of an endpoint buffer, but also determine its configuration and control. Most of the configuration is done with the BD Status register, BDnSTAT. Each BD has its own unique and correspondingly numbered BDnSTAT register. FIGURE 17-6: EXAMPLE OF A BUFFER DESCRIPTOR Unlike other control registers, the bit configuration for the BDnSTAT register is context sensitive. There are two distinct configurations, depending on whether the microcontroller or the USB module is modifying the BD and buffer at a particular time. Only three bit definitions are shared between the two. 17.4.1.1 Buffer Ownership Because the buffers and their BDs are shared between the CPU and the USB module, a simple semaphore mechanism is used to distinguish which is allowed to update the BD and associated buffers in memory. This is done by using the UOWN bit (BDnSTAT<7>) as a semaphore to distinguish which is allowed to update the BD and associated buffers in memory. UOWN is the only bit that is shared between the two configurations of BDnSTAT. When UOWN is clear, the BD entry is “owned” by the microcontroller core. When the UOWN bit is set, the BD entry and the buffer memory are “owned” by the USB peripheral. The core should not modify the BD or its corresponding data buffer during this time. Note that the microcontroller core can still read BDnSTAT while the SIE owns the buffer and vice versa. The buffer descriptors have a different meaning based on the source of the register update. Prior to placing ownership with the USB peripheral, the user can configure the basic operation of the peripheral through the BDnSTAT bits. During this time, the byte count and buffer location registers can also be set. When UOWN is set, the user can no longer depend on the values that were written to the BDs. From this point, the SIE updates the BDs as necessary, overwriting the original BD values. The BDnSTAT register is updated by the SIE with the token PID and the transfer count, BDnCNT, is updated. 400h USB Data Buffer Buffer BD0STAT BD0CNT BD0ADRL BD0ADRH 401h 402h 403h 500h 53Fh Descriptor Note: Memory regions not to scale. 40h 00h 05h Starting Size of Block (xxh) Address Registers Contents Address © 2009 Microchip Technology Inc. DS39632E-page 175 PIC18F2455/2550/4455/4550 The BDnSTAT byte of the BDT should always be the last byte updated when preparing to arm an endpoint. The SIE will clear the UOWN bit when a transaction has completed. The only exception to this is when KEN is enabled and/or BSTALL is enabled. No hardware mechanism exists to block access when the UOWN bit is set. Thus, unexpected behavior can occur if the microcontroller attempts to modify memory when the SIE owns it. Similarly, reading such memory may produce inaccurate data until the USB peripheral returns ownership to the microcontroller. 17.4.1.2 BDnSTAT Register (CPU Mode) When UOWN = 0, the microcontroller core owns the BD. At this point, the other seven bits of the register take on control functions. The Keep Enable bit, KEN (BDnSTAT<5>), determines if a BD stays enabled. If the bit is set, once the UOWN bit is set, it will remain owned by the SIE independent of the endpoint activity. This prevents the USTAT FIFO from being updated, as well as the transaction complete interrupt from being set for the endpoint. This feature should only be enabled when the Streaming Parallel Port is selected as the data I/O channel instead of USB RAM. The Address Increment Disable bit, INCDIS (BDnSTAT<4>), controls the SIE’s automatic address increment function. Setting INCDIS disables the auto-increment of the buffer address by the SIE for each byte transmitted or received. This feature should only be enabled when using the Streaming Parallel Port, where each data byte is processed to or from the same memory location. The Data Toggle Sync Enable bit, DTSEN (BDnSTAT<3>), controls data toggle parity checking. Setting DTSEN enables data toggle synchronization by the SIE. When enabled, it checks the data packet’s parity against the value of DTS (BDnSTAT<6>). If a packet arrives with an incorrect synchronization, the data will essentially be ignored. It will not be written to the USB RAM and the USB transfer complete interrupt flag will not be set. The SIE will send an ACK token back to the host to Acknowledge receipt, however. The effects of the DTSEN bit on the SIE are summarized in Table 17-3. The Buffer Stall bit, BSTALL (BDnSTAT<2>), provides support for control transfers, usually one-time stalls on Endpoint 0. It also provides support for the SET_FEATURE/CLEAR_FEATURE commands specified in Chapter 9 of the USB specification; typically, continuous STALLs to any endpoint other than the default control endpoint. The BSTALL bit enables buffer stalls. Setting BSTALL causes the SIE to return a STALL token to the host if a received token would use the BD in that location. The EPSTALL bit in the corresponding UEPn control register is set and a STALL interrupt is generated when a STALL is issued to the host. The UOWN bit remains set and the BDs are not changed unless a SETUP token is received. In this case, the STALL condition is cleared and the ownership of the BD is returned to the microcontroller core. The BD9:BD8 bits (BDnSTAT<1:0>) store the two most significant digits of the SIE byte count; the lower 8 digits are stored in the corresponding BDnCNT register. See Section 17.4.2 “BD Byte Count” for more information. TABLE 17-3: EFFECT OF DTSEN BIT ON ODD/EVEN (DATA0/DATA1) PACKET RECEPTION OUT Packet from Host BDnSTAT Settings Device Response after Receiving Packet DTSEN DTS Handshake UOWN TRNIF BDnSTAT and USTAT Status DATA0 1 0 ACK 0 1 Updated DATA1 1 0 ACK 1 0 Not Updated DATA1 1 1 ACK 0 1 Updated DATA0 1 1 ACK 1 0 Not Updated Either 0 x ACK 0 1 Updated Either, with error x x NAK 1 0 Not Updated Legend: x = don’t care PIC18F2455/2550/4455/4550 DS39632E-page 176 © 2009 Microchip Technology Inc. REGISTER 17-5: BDnSTAT: BUFFER DESCRIPTOR n STATUS REGISTER (BD0STAT THROUGH BD63STAT), CPU MODE (DATA IS WRITTEN TO THE SIDE) R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x UOWN(1) DTS(2) KEN INCDIS DTSEN BSTALL BC9 BC8 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 UOWN: USB Own bit(1) 0 = The microcontroller core owns the BD and its corresponding buffer bit 6 DTS: Data Toggle Synchronization bit(2) 1 = Data 1 packet 0 = Data 0 packet bit 5 KEN: BD Keep Enable bit 1 = USB will keep the BD indefinitely once UOWN is set (required for SPP endpoint configuration) 0 = USB will hand back the BD once a token has been processed bit 4 INCDIS: Address Increment Disable bit 1 = Address increment disabled (required for SPP endpoint configuration) 0 = Address increment enabled bit 3 DTSEN: Data Toggle Synchronization Enable bit 1 = Data toggle synchronization is enabled; data packets with incorrect Sync value will be ignored except for a SETUP transaction, which is accepted even if the data toggle bits do not match 0 = No data toggle synchronization is performed bit 2 BSTALL: Buffer Stall Enable bit 1 = Buffer stall enabled; STALL handshake issued if a token is received that would use the BD in the given location (UOWN bit remains set, BD value is unchanged) 0 = Buffer stall disabled bit 1-0 BC9:BC8: Byte Count 9 and 8 bits The byte count bits represent the number of bytes that will be transmitted for an IN token or received during an OUT token. Together with BC<7:0>, the valid byte counts are 0-1023. Note 1: This bit must be initialized by the user to the desired value prior to enabling the USB module. 2: This bit is ignored unless DTSEN = 1. © 2009 Microchip Technology Inc. DS39632E-page 177 PIC18F2455/2550/4455/4550 17.4.1.3 BDnSTAT Register (SIE Mode) When the BD and its buffer are owned by the SIE, most of the bits in BDnSTAT take on a different meaning. The configuration is shown in Register 17-6. Once UOWN is set, any data or control settings previously written there by the user will be overwritten with data from the SIE. The BDnSTAT register is updated by the SIE with the token Packet Identifier (PID) which is stored in BDnSTAT<5:3>. The transfer count in the corresponding BDnCNT register is updated. Values that overflow the 8-bit register carry over to the two most significant digits of the count, stored in BDnSTAT<1:0>. 17.4.2 BD BYTE COUNT The byte count represents the total number of bytes that will be transmitted during an IN transfer. After an IN transfer, the SIE will return the number of bytes sent to the host. For an OUT transfer, the byte count represents the maximum number of bytes that can be received and stored in USB RAM. After an OUT transfer, the SIE will return the actual number of bytes received. If the number of bytes received exceeds the corresponding byte count, the data packet will be rejected and a NAK handshake will be generated. When this happens, the byte count will not be updated. The 10-bit byte count is distributed over two registers. The lower 8 bits of the count reside in the BDnCNT register. The upper two bits reside in BDnSTAT<1:0>. This represents a valid byte range of 0 to 1023. 17.4.3 BD ADDRESS VALIDATION The BD Address register pair contains the starting RAM address location for the corresponding endpoint buffer. For an endpoint starting location to be valid, it must fall in the range of the USB RAM, 400h to 7FFh. No mechanism is available in hardware to validate the BD address. If the value of the BD address does not point to an address in the USB RAM, or if it points to an address within another endpoint’s buffer, data is likely to be lost or overwritten. Similarly, overlapping a receive buffer (OUT endpoint) with a BD location in use can yield unexpected results. When developing USB applications, the user may want to consider the inclusion of software-based address validation in their code. REGISTER 17-6: BDnSTAT: BUFFER DESCRIPTOR n STATUS REGISTER (BD0STAT THROUGH BD63STAT), SIE MODE (DATA RETURNED BY THE SIDE TO THE MICROCONTROLLER) R/W-x U-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x UOWN — PID3 PID2 PID1 PID0 BC9 BC8 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 UOWN: USB Own bit 1 = The SIE owns the BD and its corresponding buffer bit 6 Reserved: Not written by the SIE bit 5-2 PID3:PID0: Packet Identifier bits The received token PID value of the last transfer (IN, OUT or SETUP transactions only). bit 1-0 BC9:BC8: Byte Count 9 and 8 bits These bits are updated by the SIE to reflect the actual number of bytes received on an OUT transfer and the actual number of bytes transmitted on an IN transfer. PIC18F2455/2550/4455/4550 DS39632E-page 178 © 2009 Microchip Technology Inc. 17.4.4 PING-PONG BUFFERING An endpoint is defined to have a ping-pong buffer when it has two sets of BD entries: one set for an Even transfer and one set for an Odd transfer. This allows the CPU to process one BD while the SIE is processing the other BD. Double-buffering BDs in this way allows for maximum throughput to/from the USB. The USB module supports four modes of operation: • No ping-pong support • Ping-pong buffer support for OUT Endpoint 0 only • Ping-pong buffer support for all endpoints • Ping-pong buffer support for all other Endpoints except Endpoint 0 The ping-pong buffer settings are configured using the PPB1:PPB0 bits in the UCFG register. The USB module keeps track of the Ping-Pong Pointer individually for each endpoint. All pointers are initially reset to the Even BD when the module is enabled. After the completion of a transaction (UOWN cleared by the SIE), the pointer is toggled to the Odd BD. After the completion of the next transaction, the pointer is toggled back to the Even BD and so on. The Even/Odd status of the last transaction is stored in the PPBI bit of the USTAT register. The user can reset all Ping-Pong Pointers to Even using the PPBRST bit. Figure 17-7 shows the four different modes of operation and how USB RAM is filled with the BDs. BDs have a fixed relationship to a particular endpoint, depending on the buffering configuration. The mapping of BDs to endpoints is detailed in Table 17-4. This relationship also means that gaps may occur in the BDT if endpoints are not enabled contiguously. This theoretically means that the BDs for disabled endpoints could be used as buffer space. In practice, users should avoid using such spaces in the BDT unless a method of validating BD addresses is implemented. FIGURE 17-7: BUFFER DESCRIPTOR TABLE MAPPING FOR BUFFERING MODES EP1 IN Even EP1 OUT Even EP1 OUT Odd EP1 IN Odd Descriptor Descriptor Descriptor Descriptor EP1 IN EP15 IN EP1 OUT EP0 OUT PPB1:PPB0 = 00 EP0 IN EP1 IN No Ping-Pong EP15 IN EP0 IN EP0 OUT Even PPB1:PPB0 = 01 EP0 OUT Odd EP1 OUT Ping-Pong Buffer EP15 IN Odd EP0 IN Even EP0 OUT Even PPB1:PPB0 = 10 EP0 OUT Odd EP0 IN Odd Ping-Pong Buffers Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor Descriptor 400h 4FFh 4FFh 4FFh 400h 400h 47Fh 483h Available as Data RAM Available as Data RAM Maximum Memory Used: 128 bytes Maximum BDs: 32 (BD0 to BD31) Maximum Memory Used: 132 bytes Maximum BDs: 33 (BD0 to BD32) Maximum Memory Used: 256 bytes Maximum BDs: 64 (BD0 to BD63) Note: Memory area not shown to scale. Descriptor Descriptor Descriptor Descriptor Buffers on EP0 OUT on all EPs EP1 IN Even EP1 OUT Even EP1 OUT Odd EP1 IN Odd Descriptor Descriptor Descriptor Descriptor EP15 IN Odd EP0 OUT PPB1:PPB0 = 11 EP0 IN Ping-Pong Buffers Descriptor Descriptor Descriptor 4FFh 400h Maximum Memory Used: 248 bytes Maximum BDs: 62 (BD0 to BD61) on all other EPs except EP0 Available as Data RAM 4F7h © 2009 Microchip Technology Inc. DS39632E-page 179 PIC18F2455/2550/4455/4550 TABLE 17-4: ASSIGNMENT OF BUFFER DESCRIPTORS FOR THE DIFFERENT BUFFERING MODES TABLE 17-5: SUMMARY OF USB BUFFER DESCRIPTOR TABLE REGISTERS Endpoint BDs Assigned to Endpoint Mode 0 (No Ping-Pong) Mode 1 (Ping-Pong on EP0 OUT) Mode 2 (Ping-Pong on all EPs) Mode 3 (Ping-Pong on all other EPs, except EP0) Out In Out In Out In Out In 0 0 1 0 (E), 1 (O) 2 0 (E), 1 (O) 2 (E), 3 (O) 0 1 1 2 3 3 4 4 (E), 5 (O) 6 (E), 7 (O) 2 (E), 3 (O) 4 (E), 5 (O) 2 4 5 5 6 8 (E), 9 (O) 10 (E), 11 (O) 6 (E), 7 (O) 8 (E), 9 (O) 3 6 7 7 8 12 (E), 13 (O) 14 (E), 15 (O) 10 (E), 11 (O) 12 (E), 13 (O) 4 8 9 9 10 16 (E), 17 (O) 18 (E), 19 (O) 14 (E), 15 (O) 16 (E), 17 (O) 5 10 11 11 12 20 (E), 21 (O) 22 (E), 23 (O) 18 (E), 19 (O) 20 (E), 21 (O) 6 12 13 13 14 24 (E), 25 (O) 26 (E), 27 (O) 22 (E), 23 (O) 24 (E), 25 (O) 7 14 15 15 16 28 (E), 29 (O) 30 (E), 31 (O) 26 (E), 27 (O) 28 (E), 29 (O) 8 16 17 17 18 32 (E), 33 (O) 34 (E), 35 (O) 30 (E), 31 (O) 32 (E), 33 (O) 9 18 19 19 20 36 (E), 37 (O) 38 (E), 39 (O) 34 (E), 35 (O) 36 (E), 37 (O) 10 20 21 21 22 40 (E), 41 (O) 42 (E), 43 (O) 38 (E), 39 (O) 40 (E), 41 (O) 11 22 23 23 24 44 (E), 45 (O) 46 (E), 47 (O) 42 (E), 43 (O) 44 (E), 45 (O) 12 24 25 25 26 48 (E), 49 (O) 50 (E), 51 (O) 46 (E), 47 (O) 48 (E), 49 (O) 13 26 27 27 28 52 (E), 53 (O) 54 (E), 55 (O) 50 (E), 51 (O) 52 (E), 53 (O) 14 28 29 29 30 56 (E), 57 (O) 58 (E), 59 (O) 54 (E), 55 (O) 56 (E), 57 (O) 15 30 31 31 32 60 (E), 61 (O) 62 (E), 63 (O) 58 (E), 59 (O) 60 (E), 61 (O) Legend: (E) = Even transaction buffer, (O) = Odd transaction buffer Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 BDnSTAT(1) UOWN DTS(4) PID3(2) KEN(3) PID2(2) INCDIS(3) PID1(2) DTSEN(3) PID0(2) BSTALL(3) BC9 BC8 BDnCNT(1) Byte Count BDnADRL(1) Buffer Address Low BDnADRH(1) Buffer Address High Note 1: For buffer descriptor registers, n may have a value of 0 to 63. For the sake of brevity, all 64 registers are shown as one generic prototype. All registers have indeterminate Reset values (xxxx xxxx). 2: Bits 5 through 2 of the BDnSTAT register are used by the SIE to return PID3:PID0 values once the register is turned over to the SIE (UOWN bit is set). Once the registers have been under SIE control, the values written for KEN, INCDIS, DTSEN and BSTALL are no longer valid. 3: Prior to turning the buffer descriptor over to the SIE (UOWN bit is cleared), bits 5 through 2 of the BDnSTAT register are used to configure the KEN, INCDIS, DTSEN and BSTALL settings. 4: This bit is ignored unless DTSEN = 1. PIC18F2455/2550/4455/4550 DS39632E-page 180 © 2009 Microchip Technology Inc. 17.5 USB Interrupts The USB module can generate multiple interrupt conditions. To accommodate all of these interrupt sources, the module is provided with its own interrupt logic structure, similar to that of the microcontroller. USB interrupts are enabled with one set of control registers and trapped with a separate set of flag registers. All sources are funneled into a single USB interrupt request, USBIF (PIR2<5>), in the microcontroller’s interrupt logic. Figure 17-8 shows the interrupt logic for the USB module. There are two layers of interrupt registers in the USB module. The top level consists of overall USB status interrupts; these are enabled and flagged in the UIE and UIR registers, respectively. The second level consists of USB error conditions, which are enabled and flagged in the UEIR and UEIE registers. An interrupt condition in any of these triggers a USB Error Interrupt Flag (UERRIF) in the top level. Interrupts may be used to trap routine events in a USB transaction. Figure 17-9 shows some common events within a USB frame and their corresponding interrupts. FIGURE 17-8: USB INTERRUPT LOGIC FUNNEL FIGURE 17-9: EXAMPLE OF A USB TRANSACTION AND INTERRUPT EVENTS BTSEF BTSEE BTOEF BTOEE DFN8EF DFN8EE CRC16EF CRC16EE CRC5EF CRC5EE PIDEF PIDEE SOFIF SOFIE TRNIF TRNIE IDLEIF IDLEIE STALLIF STALLIE ACTVIF ACTVIE URSTIF URSTIE UERRIF UERRIE USBIF Second Level USB Interrupts (USB Error Conditions) UEIR (Flag) and UEIE (Enable) Registers Top Level USB Interrupts (USB Status Interrupts) UIR (Flag) and UIE (Enable) Registers USB Reset RESET SOF SETUP DATA STATUS SOF SETUPToken Data ACK Start-Of-Frame OUT Token Empty Data ACK IN Token Data ACK SOFIF URSTIF 1 ms Frame Differential Data From Host From Host To Host From Host To Host From Host From Host From Host To Host Transaction Control Transfer(1) Transaction Complete Note 1: The control transfer shown here is only an example showing events that can occur for every transaction. Typical control transfers will spread across multiple frames. Set TRNIF Set TRNIF Set TRNIF © 2009 Microchip Technology Inc. DS39632E-page 181 PIC18F2455/2550/4455/4550 17.5.1 USB INTERRUPT STATUS REGISTER (UIR) The USB Interrupt Status register (Register 17-7) contains the flag bits for each of the USB status interrupt sources. Each of these sources has a corresponding interrupt enable bit in the UIE register. All of the USB status flags are ORed together to generate the USBIF interrupt flag for the microcontroller’s interrupt funnel. Once an interrupt bit has been set by the SIE, it must be cleared by software by writing a ‘0’. The flag bits can also be set in software which can aid in firmware debugging. When the USB module is in the Low-Power Suspend mode (UCON<1> = 1), the SIE does not get clocked. When in this state, the SIE cannot process packets, and therefore, cannot detect new interrupt conditions other than the Activity Detect Interrupt, ACTVIF. The ACTVIF bit is typically used by USB firmware to detect when the microcontroller should bring the USB module out of the Low-Power Suspend mode (UCON<1> = 0). REGISTER 17-7: UIR: USB INTERRUPT STATUS REGISTER U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R/W-0 — SOFIF STALLIF IDLEIF(1) TRNIF(2) ACTVIF(3) UERRIF(4) URSTIF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 Unimplemented: Read as ‘0’ bit 6 SOFIF: Start-Of-Frame Token Interrupt bit 1 = A Start-Of-Frame token received by the SIE 0 = No Start-Of-Frame token received by the SIE bit 5 STALLIF: A STALL Handshake Interrupt bit 1 = A STALL handshake was sent by the SIE 0 = A STALL handshake has not been sent bit 4 IDLEIF: Idle Detect Interrupt bit(1) 1 = Idle condition detected (constant Idle state of 3 ms or more) 0 = No Idle condition detected bit 3 TRNIF: Transaction Complete Interrupt bit(2) 1 = Processing of pending transaction is complete; read USTAT register for endpoint information 0 = Processing of pending transaction is not complete or no transaction is pending bit 2 ACTVIF: Bus Activity Detect Interrupt bit(3) 1 = Activity on the D+/D- lines was detected 0 = No activity detected on the D+/D- lines bit 1 UERRIF: USB Error Condition Interrupt bit(4) 1 = An unmasked error condition has occurred 0 = No unmasked error condition has occurred. bit 0 URSTIF: USB Reset Interrupt bit 1 = Valid USB Reset occurred; 00h is loaded into UADDR register 0 = No USB Reset has occurred Note 1: Once an Idle state is detected, the user may want to place the USB module in Suspend mode. 2: Clearing this bit will cause the USTAT FIFO to advance (valid only for IN, OUT and SETUP tokens). 3: This bit is typically unmasked only following the detection of a UIDLE interrupt event. 4: Only error conditions enabled through the UEIE register will set this bit. This bit is a status bit only and cannot be set or cleared by the user. PIC18F2455/2550/4455/4550 DS39632E-page 182 © 2009 Microchip Technology Inc. 17.5.1.1 Bus Activity Detect Interrupt Bit (ACTVIF) The ACTVIF bit cannot be cleared immediately after the USB module wakes up from Suspend or while the USB module is suspended. A few clock cycles are required to synchronize the internal hardware state machine before the ACTVIF bit can be cleared by firmware. Clearing the ACTVIF bit before the internal hardware is synchronized may not have an effect on the value of ACTVIF. Additionally, if the USB module uses the clock from the 96 MHz PLL source, then after clearing the SUSPND bit, the USB module may not be immediately operational while waiting for the 96 MHz PLL to lock. The application code should clear the ACTVIF flag as shown in Example 17-1. EXAMPLE 17-1: CLEARING ACTVIF BIT (UIR<2>) Note: Only one ACTVIF interrupt is generated when resuming from the USB bus Idle condition. If user firmware clears the ACTVIF bit, the bit will not immediately become set again, even when there is continuous bus traffic. Bus traffic must cease long enough to generate another IDLEIF condition before another ACTVIF interrupt can be generated. Assembly: BCF UCON, SUSPND Loop: BCF UIR, ACTVIF BTFSC UIR, ACTVIF BRA Loop Done: C: UCONbits.SUSPND = 0; while (UIRbits.ACTVIF) { UIRbits.ACTVIF = 0; } © 2009 Microchip Technology Inc. DS39632E-page 183 PIC18F2455/2550/4455/4550 17.5.2 USB INTERRUPT ENABLE REGISTER (UIE) The USB Interrupt Enable register (Register 17-8) contains the enable bits for the USB status interrupt sources. Setting any of these bits will enable the respective interrupt source in the UIR register. The values in this register only affect the propagation of an interrupt condition to the microcontroller’s interrupt logic. The flag bits are still set by their interrupt conditions, allowing them to be polled and serviced without actually generating an interrupt. REGISTER 17-8: UIE: USB INTERRUPT ENABLE REGISTER U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 — SOFIE STALLIE IDLEIE TRNIE ACTVIE UERRIE URSTIE bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 Unimplemented: Read as ‘0’ bit 6 SOFIE: Start-Of-Frame Token Interrupt Enable bit 1 = Start-Of-Frame token interrupt enabled 0 = Start-Of-Frame token interrupt disabled bit 5 STALLIE: STALL Handshake Interrupt Enable bit 1 = STALL interrupt enabled 0 = STALL interrupt disabled bit 4 IDLEIE: Idle Detect Interrupt Enable bit 1 = Idle detect interrupt enabled 0 = Idle detect interrupt disabled bit 3 TRNIE: Transaction Complete Interrupt Enable bit 1 = Transaction interrupt enabled 0 = Transaction interrupt disabled bit 2 ACTVIE: Bus Activity Detect Interrupt Enable bit 1 = Bus activity detect interrupt enabled 0 = Bus activity detect interrupt disabled bit 1 UERRIE: USB Error Interrupt Enable bit 1 = USB error interrupt enabled 0 = USB error interrupt disabled bit 0 URSTIE: USB Reset Interrupt Enable bit 1 = USB Reset interrupt enabled 0 = USB Reset interrupt disabled PIC18F2455/2550/4455/4550 DS39632E-page 184 © 2009 Microchip Technology Inc. 17.5.3 USB ERROR INTERRUPT STATUS REGISTER (UEIR) The USB Error Interrupt Status register (Register 17-9) contains the flag bits for each of the error sources within the USB peripheral. Each of these sources is controlled by a corresponding interrupt enable bit in the UEIE register. All of the USB error flags are ORed together to generate the USB Error Interrupt Flag (UERRIF) at the top level of the interrupt logic. Each error bit is set as soon as the error condition is detected. Thus, the interrupt will typically not correspond with the end of a token being processed. Once an interrupt bit has been set by the SIE, it must be cleared by software by writing a ‘0’. REGISTER 17-9: UEIR: USB ERROR INTERRUPT STATUS REGISTER R/C-0 U-0 U-0 R/C-0 R/C-0 R/C-0 R/C-0 R/C-0 BTSEF — — BTOEF DFN8EF CRC16EF CRC5EF PIDEF bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 BTSEF: Bit Stuff Error Flag bit 1 = A bit stuff error has been detected 0 = No bit stuff error bit 6-5 Unimplemented: Read as ‘0’ bit 4 BTOEF: Bus Turnaround Time-out Error Flag bit 1 = Bus turnaround time-out has occurred (more than 16 bit times of Idle from previous EOP elapsed) 0 = No bus turnaround time-out bit 3 DFN8EF: Data Field Size Error Flag bit 1 = The data field was not an integral number of bytes 0 = The data field was an integral number of bytes bit 2 CRC16EF: CRC16 Failure Flag bit 1 = The CRC16 failed 0 = The CRC16 passed bit 1 CRC5EF: CRC5 Host Error Flag bit 1 = The token packet was rejected due to a CRC5 error 0 = The token packet was accepted bit 0 PIDEF: PID Check Failure Flag bit 1 = PID check failed 0 = PID check passed © 2009 Microchip Technology Inc. DS39632E-page 185 PIC18F2455/2550/4455/4550 17.5.4 USB ERROR INTERRUPT ENABLE REGISTER (UEIE) The USB Error Interrupt Enable register (Register 17-10) contains the enable bits for each of the USB error interrupt sources. Setting any of these bits will enable the respective error interrupt source in the UEIR register to propagate into the UERR bit at the top level of the interrupt logic. As with the UIE register, the enable bits only affect the propagation of an interrupt condition to the microcontroller’s interrupt logic. The flag bits are still set by their interrupt conditions, allowing them to be polled and serviced without actually generating an interrupt. REGISTER 17-10: UEIE: USB ERROR INTERRUPT ENABLE REGISTER R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 BTSEE — — BTOEE DFN8EE CRC16EE CRC5EE PIDEE bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 BTSEE: Bit Stuff Error Interrupt Enable bit 1 = Bit stuff error interrupt enabled 0 = Bit stuff error interrupt disabled bit 6-5 Unimplemented: Read as ‘0’ bit 4 BTOEE: Bus Turnaround Time-out Error Interrupt Enable bit 1 = Bus turnaround time-out error interrupt enabled 0 = Bus turnaround time-out error interrupt disabled bit 3 DFN8EE: Data Field Size Error Interrupt Enable bit 1 = Data field size error interrupt enabled 0 = Data field size error interrupt disabled bit 2 CRC16EE: CRC16 Failure Interrupt Enable bit 1 = CRC16 failure interrupt enabled 0 = CRC16 failure interrupt disabled bit 1 CRC5EE: CRC5 Host Error Interrupt Enable bit 1 = CRC5 host error interrupt enabled 0 = CRC5 host error interrupt disabled bit 0 PIDEE: PID Check Failure Interrupt Enable bit 1 = PID check failure interrupt enabled 0 = PID check failure interrupt disabled PIC18F2455/2550/4455/4550 DS39632E-page 186 © 2009 Microchip Technology Inc. 17.6 USB Power Modes Many USB applications will likely have several different sets of power requirements and configuration. The most common power modes encountered are Bus Power Only, Self-Power Only and Dual Power with Self-Power Dominance. The most common cases are presented here. 17.6.1 BUS POWER ONLY In Bus Power Only mode, all power for the application is drawn from the USB (Figure 17-10). This is effectively the simplest power method for the device. In order to meet the inrush current requirements of the USB 2.0 specifications, the total effective capacitance appearing across VBUS and ground must be no more than 10 μF. If not, some kind of inrush limiting is required. For more details, see Section 7.2.4 of the USB 2.0 specification. According to the USB 2.0 specification, all USB devices must also support a Low-Power Suspend mode. In the USB Suspend mode, devices must consume no more than 2.5 mA from the 5V VBUS line of the USB cable. The host signals the USB device to enter the Suspend mode by stopping all USB traffic to that device for more than 3 ms. This condition will cause the IDLEIF bit in the UIR register to become set. During the USB Suspend mode, the D+ or D- pull-up resistor must remain active, which will consume some of the allowed suspend current: 2.5 mA budget. FIGURE 17-10: BUS POWER ONLY 17.6.2 SELF-POWER ONLY In Self-Power Only mode, the USB application provides its own power, with very little power being pulled from the USB. Figure 17-11 shows an example. Note that an attach indication is added to indicate when the USB has been connected and the host is actively powering VBUS. In order to meet compliance specifications, the USB module (and the D+ or D- pull-up resistor) should not be enabled until the host actively drives VBUS high. One of the I/O pins may be used for this purpose. The application should never source any current onto the 5V VBUS pin of the USB cable. FIGURE 17-11: SELF-POWER ONLY 17.6.3 DUAL POWER WITH SELF-POWER DOMINANCE Some applications may require a dual power option. This allows the application to use internal power primarily, but switch to power from the USB when no internal power is available. Figure 17-12 shows a simple Dual Power with Self-Power Dominance example, which automatically switches between Self-Power Only and USB Bus Power Only modes. Dual power devices also must meet all of the special requirements for inrush current and Suspend mode current and must not enable the USB module until VBUS is driven high. For descriptions of those requirements, see Section 17.6.1 “Bus Power Only” and Section 17.6.2 “Self-Power Only”. Additionally, dual power devices must never source current onto the 5V VBUS pin of the USB cable. FIGURE 17-12: DUAL POWER EXAMPLE VDD VUSB VSS VBUS ~5V Note: Users should keep in mind the limits for devices drawing power from the USB. According to USB specification 2.0, this cannot exceed 100 mA per low-power device or 500 mA per high-power device. VDD VUSB VSS VSELF ~5V I/O pin Attach Sense 100 kΩ VBUS ~5V 100 kΩ VDD VUSB I/O pin VSS Attach Sense VBUS VSELF 100 kΩ ~5V ~5V 100 kΩ © 2009 Microchip Technology Inc. DS39632E-page 187 PIC18F2455/2550/4455/4550 17.7 Streaming Parallel Port The Streaming Parallel Port (SPP) is an alternate route option for data besides USB RAM. Using the SPP, an endpoint can be configured to send data to or receive data directly from external hardware. This methodology presents design possibilities where the microcontroller acts as a data manager, allowing the SPP to pass large blocks of data without the microcontroller actually processing it. An application example might include a data acquisition system, where data is streamed from an external FIFO through USB to the host computer. In this case, endpoint control is managed by the microcontroller and raw data movement is processed externally. The SPP is enabled as a USB endpoint port through the associated endpoint buffer descriptor. The endpoint must be enabled as follows: 1. Set BDnADRL:BDnADRH to point to FFFFh. 2. Set the KEN bit (BDnSTAT<5>) to let SIE keep control of the buffer. 3. Set the INCDIS bit (BDnSTAT<4>) to disable automatic address increment. Refer to Section 18.0 “Streaming Parallel Port” for more information about the SPP. 17.8 Oscillator The USB module has specific clock requirements. For full-speed operation, the clock source must be 48 MHz. Even so, the microcontroller core and other peripherals are not required to run at that clock speed or even from the same clock source. Available clocking options are described in detail in Section 2.3 “Oscillator Settings for USB”. TABLE 17-6: REGISTERS ASSOCIATED WITH USB MODULE OPERATION(1) Note 1: If an endpoint is configured to use the SPP, the SPP module must also be configured to use the USB module. Otherwise, unexpected operation may occur. 2: In addition, if an endpoint is configured to use the SPP, the data transfer type of that endpoint must be isochronous only. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Details on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the USB module. Note 1: This table includes only those hardware mapped SFRs located in Bank 15 of the data memory space. The Buffer Descriptor registers, which are mapped into Bank 4 and are not true SFRs, are listed separately in Table 17-5. PIC18F2455/2550/4455/4550 DS39632E-page 188 © 2009 Microchip Technology Inc. PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 UCON — PPBRST SE0 PKTDIS USBEN RESUME SUSPND — 57 UCFG UTEYE UOEMON — UPUEN UTRDIS FSEN PPB1 PPB0 57 USTAT — ENDP3 ENDP2 ENDP1 ENDP0 DIR PPBI — 57 UADDR — ADDR6 ADDR5 ADDR4 ADDR3 ADDR2 ADDR1 ADDR0 57 UFRML FRM7 FRM6 FRM5 FRM4 FRM3 FRM2 FRM1 FRM0 57 UFRMH — — — — — FRM10 FRM9 FRM8 57 UIR — SOFIF STALLIF IDLEIF TRNIF ACTVIF UERRIF URSTIF 57 UIE — SOFIE STALLIE IDLEIE TRNIE ACTVIE UERRIE URSTIE 57 UEIR BTSEF — — BTOEF DFN8EF CRC16EF CRC5EF PIDEF 57 UEIE BTSEE — — BTOEE DFN8EE CRC16EE CRC5EE PIDEE 57 UEP0 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP1 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP2 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP3 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP4 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP5 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP6 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP7 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP8 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP9 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP10 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP11 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP12 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP13 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP14 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 UEP15 — — — EPHSHK EPCONDIS EPOUTEN EPINEN EPSTALL 57 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Details on page Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the USB module. Note 1: This table includes only those hardware mapped SFRs located in Bank 15 of the data memory space. The Buffer Descriptor registers, which are mapped into Bank 4 and are not true SFRs, are listed separately in Table 17-5. © 2009 Microchip Technology Inc. DS39632E-page 189 PIC18F2455/2550/4455/4550 17.10 Overview of USB This section presents some of the basic USB concepts and useful information necessary to design a USB device. Although much information is provided in this section, there is a plethora of information provided within the USB specifications and class specifications. Thus, the reader is encouraged to refer to the USB specifications for more information (www.usb.org). If you are very familiar with the details of USB, then this section serves as a basic, high-level refresher of USB. 17.10.1 LAYERED FRAMEWORK USB device functionality is structured into a layered framework graphically shown in Figure 17-13. Each level is associated with a functional level within the device. The highest layer, other than the device, is the configuration. A device may have multiple configurations. For example, a particular device may have multiple power requirements based on Self-Power Only or Bus Power Only modes. For each configuration, there may be multiple interfaces. Each interface could support a particular mode of that configuration. Below the interface is the endpoint(s). Data is directly moved at this level. There can be as many as 16 bidirectional endpoints. Endpoint 0 is always a control endpoint and by default, when the device is on the bus, Endpoint 0 must be available to configure the device. 17.10.2 FRAMES Information communicated on the bus is grouped into 1 ms time slots, referred to as frames. Each frame can contain many transactions to various devices and endpoints. Figure 17-9 shows an example of a transaction within a frame. 17.10.3 TRANSFERS There are four transfer types defined in the USB specification. • Isochronous: This type provides a transfer method for large amounts of data (up to 1023 bytes) with timely delivery ensured; however, the data integrity is not ensured. This is good for streaming applications where small data loss is not critical, such as audio. • Bulk: This type of transfer method allows for large amounts of data to be transferred with ensured data integrity; however, the delivery timeliness is not ensured. • Interrupt: This type of transfer provides for ensured timely delivery for small blocks of data, plus data integrity is ensured. • Control: This type provides for device setup control. While full-speed devices support all transfer types, low-speed devices are limited to interrupt and control transfers only. 17.10.4 POWER Power is available from the Universal Serial Bus. The USB specification defines the bus power requirements. Devices may either be self-powered or bus powered. Self-powered devices draw power from an external source, while bus powered devices use power supplied from the bus. FIGURE 17-13: USB LAYERS Device Configuration Interface Endpoint Interface Endpoint Endpoint Endpoint Endpoint To other Configurations (if any) To other Interfaces (if any) PIC18F2455/2550/4455/4550 DS39632E-page 190 © 2009 Microchip Technology Inc. The USB specification limits the power taken from the bus. Each device is ensured 100 mA at approximately 5V (one unit load). Additional power may be requested, up to a maximum of 500 mA. Note that power above one unit load is a request and the host or hub is not obligated to provide the extra current. Thus, a device capable of consuming more than one unit load must be able to maintain a low-power configuration of a one unit load or less, if necessary. The USB specification also defines a Suspend mode. In this situation, current must be limited to 2.5 mA, averaged over 1 second. A device must enter a Suspend state after 3 ms of inactivity (i.e., no SOF tokens for 3 ms). A device entering Suspend mode must drop current consumption within 10 ms after Suspend. Likewise, when signaling a wake-up, the device must signal a wake-up within 10 ms of drawing current above the Suspend limit. 17.10.5 ENUMERATION When the device is initially attached to the bus, the host enters an enumeration process in an attempt to identify the device. Essentially, the host interrogates the device, gathering information such as power consumption, data rates and sizes, protocol and other descriptive information; descriptors contain this information. A typical enumeration process would be as follows: 1. USB Reset: Reset the device. Thus, the device is not configured and does not have an address (address 0). 2. Get Device Descriptor: The host requests a small portion of the device descriptor. 3. USB Reset: Reset the device again. 4. Set Address: The host assigns an address to the device. 5. Get Device Descriptor: The host retrieves the device descriptor, gathering info such as manufacturer, type of device, maximum control packet size. 6. Get configuration descriptors. 7. Get any other descriptors. 8. Set a configuration. The exact enumeration process depends on the host. 17.10.6 DESCRIPTORS There are eight different standard descriptor types of which five are most important for this device. 17.10.6.1 Device Descriptor The device descriptor provides general information, such as manufacturer, product number, serial number, the class of the device and the number of configurations. There is only one device descriptor. 17.10.6.2 Configuration Descriptor The configuration descriptor provides information on the power requirements of the device and how many different interfaces are supported when in this configuration. There may be more than one configuration for a device (i.e., low-power and high-power configurations). 17.10.6.3 Interface Descriptor The interface descriptor details the number of endpoints used in this interface, as well as the class of the interface. There may be more than one interface for a configuration. 17.10.6.4 Endpoint Descriptor The endpoint descriptor identifies the transfer type (Section 17.10.3 “Transfers”) and direction, as well as some other specifics for the endpoint. There may be many endpoints in a device and endpoints may be shared in different configurations. 17.10.6.5 String Descriptor Many of the previous descriptors reference one or more string descriptors. String descriptors provide human readable information about the layer (Section 17.10.1 “Layered Framework”) they describe. Often these strings show up in the host to help the user identify the device. String descriptors are generally optional to save memory and are encoded in a unicode format. 17.10.7 BUS SPEED Each USB device must indicate its bus presence and speed to the host. This is accomplished through a 1.5 kΩ resistor which is connected to the bus at the time of the attachment event. Depending on the speed of the device, the resistor either pulls up the D+ or D- line to 3.3V. For a low-speed device, the pull-up resistor is connected to the D- line. For a full-speed device, the pull-up resistor is connected to the D+ line. 17.10.8 CLASS SPECIFICATIONS AND DRIVERS USB specifications include class specifications which operating system vendors optionally support. Examples of classes include Audio, Mass Storage, Communications and Human Interface (HID). In most cases, a driver is required at the host side to ‘talk’ to the USB device. In custom applications, a driver may need to be developed. Fortunately, drivers are available for most common host systems for the most common classes of devices. Thus, these drivers can be reused. © 2009 Microchip Technology Inc. DS39632E-page 191 PIC18F2455/2550/4455/4550 18.0 STREAMING PARALLEL PORT PIC18F4455/4550 USB devices provide a Streaming Parallel Port as a high-speed interface for moving data to and from an external system. This parallel port operates as a master port, complete with chip select and clock outputs to control the movement of data to slave devices. Data can be channelled either directly to the USB SIE or to the microprocessor core. Figure 18-1 shows a block view of the SPP data path. FIGURE 18-1: SPP DATA PATH In addition, the SPP can provide time multiplexed addressing information along with the data by using the second strobe output. Thus, the USB endpoint number can be written in conjunction with the data for that endpoint. 18.1 SPP Configuration The operation of the SPP is controlled by two registers: SPPCON and SPPCFG. The SPPCON register (Register 18-1) controls the overall operation of the parallel port and determines if it operates under USB or microcontroller control. The SPPCFG register (Register 18-2) controls timing configuration and pin outputs. 18.1.1 ENABLING THE SPP To enable the SPP, set the SPPEN bit (SPPCON<0>). In addition, the TRIS bits for the corresponding SPP pins must be properly configured. At a minimum: • Bits TRISD<7:0> must be set (= 1) • Bits TRISE<2:1> must be cleared (= 0) If CK1SPP is to be used: • Bit TRISE<0> must be cleared (= 0) If CSPP is to be used: • Bit TRISB<4> must be cleared (= 0) Note: The Streaming Parallel Port is only available on 40/44-pin devices. SPP Logic CK2SPP OESPP CSSPP SPP<7:0> USB CK1SPP CPU PIC18F4455/4550 SIE REGISTER 18-1: SPPCON: SPP CONTROL REGISTER U-0 U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 — — — — — — SPPOWN SPPEN bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-2 Unimplemented: Read as ‘0’ bit 1 SPPOWN: SPP Ownership bit 1 = USB peripheral controls the SPP 0 = Microcontroller directly controls the SPP bit 0 SPPEN: SPP Enable bit 1 = SPP is enabled 0 = SPP is disabled PIC18F2455/2550/4455/4550 DS39632E-page 192 © 2009 Microchip Technology Inc. 18.1.2 CLOCKING DATA The SPP has four control outputs: • Two separate clock outputs (CK1SPP and CK2SPP) • Output enable (OESPP) • Chip select (CSSPP) Together, they allow for several different configurations for controlling the flow of data to slave devices. When all control outputs are used, the three main options are: • CLK1 clocks endpoint address information while CLK2 clocks data • CLK1 clocks write operations while CLK2 clocks reads • CLK1 clocks Odd address data while CLK2 clocks Even address data Additional control options are derived by disabling the CK1SPP and CSSPP outputs. These are enabled or disabled with the CLK1EN and CSEN bits, respectively, located in Register 18-2. 18.1.3 WAIT STATES The SPP is designed with the capability of adding wait states to read and write operations. This allows access to parallel devices that require extra time for access. Wait state clocking is based on the data source clock. If the SPP is configured to operate as a USB endpoint, then wait states are based on the USB clock. Likewise, if the SPP is configured to operate from the microcontroller, then wait states are based on the instruction rate (FOSC/4). The WS3:WS0 bits set the wait states used by the SPP, with a range of no wait states to 30 wait states, in multiples of two. The wait states are added symmetrically to all transactions, with one-half added following each of the two clock cycles normally required for the transaction. Figure 18-3 and Figure 18-4 show signalling examples with 4 wait states added to each transaction. 18.1.4 SPP PULL-UPS The SPP data lines (SPP<7:0>) are equipped with internal pull-ups for applications that may leave the port in a high-impedance condition. The pull-ups are enabled using the control bit, RDPU (PORTE<7>). REGISTER 18-2: SPPCFG: SPP CONFIGURATION REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 CLKCFG1 CLKCFG0 CSEN CLK1EN WS3 WS2 WS1 WS0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-6 CLKCFG1:CLKCFG0: SPP Clock Configuration bits 1x = CLK1 toggles on read or write of an Odd endpoint address; CLK2 toggles on read or write of an Even endpoint address 01 = CLK1 toggles on write; CLK2 toggles on read 00 = CLK1 toggles only on endpoint address write; CLK2 toggles on data read or write bit 5 CSEN: SPP Chip Select Pin Enable bit 1 = RB4 pin is controlled by the SPP module and functions as SPP CS output 0 = RB4 functions as a digital I/O port bit 4 CLK1EN: SPP CLK1 Pin Enable bit 1 = RE0 pin is controlled by the SPP module and functions as SPP CLK1 output 0 = RE0 functions as a digital I/O port bit 3-0 WS3:WS0: SPP Wait States bits 1111 = 30 additional wait states 1110 = 28 additional wait states • • • • 0001 = 2 additional wait states 0000 = 0 additional wait states © 2009 Microchip Technology Inc. DS39632E-page 193 PIC18F2455/2550/4455/4550 FIGURE 18-2: TIMING FOR MICROCONTROLLER WRITE ADDRESS, WRITE DATA AND READ DATA (NO WAIT STATES) FIGURE 18-3: TIMING FOR USB WRITE ADDRESS AND DATA (4 WAIT STATES) FIGURE 18-4: TIMING FOR USB WRITE ADDRESS AND READ DATA (4 WAIT STATES) FOSC/4 OESPP CK1SPP CK2SPP CSSPP SPP<7:0> MOVWF SPPEPS MOVWF SPPDATA Write Address Write Data MOVF SPPDATA, W Read Data ADDR DATA DATA USB Clock OESPP CK1SPP CK2SPP CSSPP SPP<7:0> 2 Wait States 2 Wait States 2 Wait States 2 Wait States Write Address Write Data USB Clock OESPP CK1SPP CK2SPP CSSPP SPP<7:0> Write Address Read Data 2 Wait States 2 Wait States 2 Wait States 2 Wait States PIC18F2455/2550/4455/4550 DS39632E-page 194 © 2009 Microchip Technology Inc. 18.2 Setup for USB Control When the SPP is configured for USB operation, data can be clocked directly to and from the USB peripheral without intervention of the microcontroller; thus, no process time is required. Data is clocked into or out from the SPP with endpoint (address) information first, followed by one or more bytes of data, as shown in Figure 18-5. This is ideal for applications that require isochronous, large volume data movement. The following steps are required to set up the SPP for USB control: 1. Configure the SPP as desired, including wait states and clocks. 2. Set the SPPOWN bit for USB ownership. 3. Set the buffer descriptor starting address (BDnADRL:BDnADRH) to FFFFh. 4. Set the KEN bit (BDnSTAT<5>) so the buffer descriptor is kept indefinitely by the SIE. 5. Set the INCDIS bit (BDnSTAT<4>) to disable automatic buffer address increment. 6. Set the SPPEN bit to enable the module. 18.3 Setup for Microcontroller Control The SPP can also act as a parallel port for the microcontroller. In this mode, the SPPEPS register (Register 18-3) provides status and address write control. Data is written to and read from the SPPDATA register. When the SPP is owned by the microcontroller, the SPP clock is driven by the instruction clock (FOSC/4). The following steps are required to set up the SPP for microcontroller operation: 1. Configure the SPP as desired, including wait states and clocks. 2. Clear the SPPOWN bit. 3. Set SPPEN to enable the module. 18.3.1 SPP INTERRUPTS When owned by the microcontroller core, control can generate an interrupt to notify the application when each read and write operation is completed. The interrupt flag bit is SPPIF (PIR1<7>) and is enabled by the SPPIE bit (PIE1<7>). Like all other microcontroller level interrupts, it can be set to a low or high priority. This is done with the SPPIP bit (IPR1<7>). 18.3.2 WRITING TO THE SPP Once configured, writing to the SPP is performed by writing to the SPPEPS and SPPDATA registers. If the SPP is configured to clock out endpoint address information with the data, writing to the SPPEPS register initiates the address write cycle. Otherwise, the write is started by writing the data to the SPPDATA register. The SPPBUSY bit indicates the status of the address and the data write cycles. The following is an example write sequence: 1. Write the 4-bit address to the SPPEPS register. The SPP automatically starts writing the address. If address write is not used, then skip to step 3. 2. Monitor the SPPBUSY bit to determine when the address has been sent. The duration depends on the wait states. 3. Write the data to the SPPDATA register. The SPP automatically starts writing the data. 4. Monitor the SPPBUSY bit to determine when the data has been sent. The duration depends on the wait states. 5. Go back to steps 1 or 3 to write a new address or data. FIGURE 18-5: TRANSFER OF DATA BETWEEN USB SIE AND SPP Note: If a USB endpoint is configured to use the SPP, the data transfer type of that endpoint must be isochronous only. Note: The SPPBUSY bit should be polled to make certain that successive writes to the SPPEPS or SPPDATA registers do not overrun the wait time due to the wait state setting. Endpoint Byte 0 Byte 1 Byte 2 Byte 3 Byte n Address Write USB endpoint number to SPP Write outbound USB data to SPP or read inbound USB data from SPP © 2009 Microchip Technology Inc. DS39632E-page 195 PIC18F2455/2550/4455/4550 18.3.3 READING FROM THE SPP Reading from the SPP involves reading the SPPDATA register. Reading the register the first time initiates the read operation. When the read is finished, indicated by the SPPBUSY bit, the SPPDATA will be loaded with the current data. The following is an example read sequence: 1. Write the 4-bit address to the SPPEPS register. The SPP automatically starts writing the address. If address write is not used then skip to step 3. 2. Monitor the SPPBUSY bit to determine when the address has been sent. The duration depends on the wait states. 3. Read the data from the SPPDATA register; the data from the previous read operation is returned. The SPP automatically starts the read cycle for the next read. 4. Monitor the SPPBUSY bit to determine when the data has been read. The duration depends on the wait states. 5. Go back to step 3 to read the current byte from the SPP and start the next read cycle. REGISTER 18-3: SPPEPS: SPP ENDPOINT ADDRESS AND STATUS REGISTER R-0 R-0 U-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 RDSPP WRSPP — SPPBUSY ADDR3 ADDR2 ADDR1 ADDR0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 RDSPP: SPP Read Status bit (Valid when SPPCON = 1, USB) 1 = The last transaction was a read from the SPP 0 = The last transaction was not a read from the SPP bit 6 WRSPP: SPP Write Status bit (Valid when SPPCON = 1, USB) 1 = The last transaction was a write to the SPP 0 = The last transaction was not a write to the SPP bit 5 Unimplemented: Read as ‘0’ bit 4 SPPBUSY: SPP Handshaking Override bit 1 = The SPP is busy 0 = The SPP is ready to accept another read or write request bit 3-0 ADDR3:ADDR0: SPP Endpoint Address bits 1111 = Endpoint Address 15 • • • • 0001 0000 = Endpoint Address 0 PIC18F2455/2550/4455/4550 DS39632E-page 196 © 2009 Microchip Technology Inc. TABLE 18-1: REGISTERS ASSOCIATED WITH THE STREAMING PARALLEL PORT Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page SPPCON(3) — — — — — — SPPOWN SPPEN 57 SPPCFG(3) CLKCFG1 CLKCFG0 CSEN CLK1EN WS3 WS2 WS1 WS0 57 SPPEPS(3) RDSPP WRSPP — SPPBUSY ADDR3 ADDR2 ADDR1 ADDR0 57 SPPDATA(3) DATA7 DATA6 DATA5 DATA4 DATA3 DATA2 DATA1 DATA0 57 PIR1 SPPIF(3) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(3) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(3) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 PORTE RDPU(3) — — — RE3(1,2) RE2(3) RE1(3) RE0(3) 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for the Streaming Parallel Port. Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0). 2: RE3 is the only PORTE bit implemented on both 28-pin and 40/44-pin devices. All other bits are implemented only when PORTE is implemented (i.e., 40/44-pin devices). 3: These registers and/or bits are unimplemented on 28-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 197 PIC18F2455/2550/4455/4550 19.0 MASTER SYNCHRONOUS SERIAL PORT (MSSP) MODULE 19.1 Master SSP (MSSP) Module Overview The Master Synchronous Serial Port (MSSP) module is a serial interface, useful for communicating with other peripheral or microcontroller devices. These peripheral devices may be serial EEPROMs, shift registers, display drivers, A/D converters, etc. The MSSP module can operate in one of two modes: • Serial Peripheral Interface (SPI) • Inter-Integrated Circuit (I2C™) - Full Master mode - Slave mode (with general address call) The I2C interface supports the following modes in hardware: • Master mode • Multi-Master mode • Slave mode 19.2 Control Registers The MSSP module has three associated control registers. These include a status register (SSPSTAT) and two control registers (SSPCON1 and SSPCON2). The use of these registers and their individual Configuration bits differ significantly depending on whether the MSSP module is operated in SPI or I2C mode. Additional details are provided under the individual sections. 19.3 SPI Mode The SPI mode allows 8 bits of data to be synchronously transmitted and received simultaneously. All four modes of the SPI are supported. To accomplish communication, typically three pins are used: • Serial Data Out (SDO) – RC7/RX/DT/SDO • Serial Data In (SDI) – RB0/AN12/INT0/FLT0/SDI/SDA • Serial Clock (SCK) – RB1/AN10/INT1/SCK/SCL Additionally, a fourth pin may be used when in a Slave mode of operation: • Slave Select (SS) – RA5/AN4/SS/HLVDIN/C2OUT Figure 19-1 shows the block diagram of the MSSP module when operating in SPI mode. FIGURE 19-1: MSSP BLOCK DIAGRAM (SPI MODE) ( ) Read Write Internal Data Bus SSPSR reg SSPM3:SSPM0 bit0 Shift Clock SS Control Enable Edge Select Clock Select TMR2 Output Prescaler TOSC 4, 16, 64 2 Edge Select 2 4 Data to TX/RX in SSPSR TRIS bit 2 SMP:CKE SDO SSPBUF reg SDI SS SCK Note: Only those pin functions relevant to SPI operation are shown here. PIC18F2455/2550/4455/4550 DS39632E-page 198 © 2009 Microchip Technology Inc. 19.3.1 REGISTERS The MSSP module has four registers for SPI mode operation. These are: • MSSP Control Register 1 (SSPCON1) • MSSP Status Register (SSPSTAT) • Serial Receive/Transmit Buffer Register (SSPBUF) • MSSP Shift Register (SSPSR) – Not directly accessible SSPCON1 and SSPSTAT are the control and status registers in SPI mode operation. The SSPCON1 register is readable and writable. The lower six bits of the SSPSTAT are read-only. The upper two bits of the SSPSTAT are read/write. SSPSR is the shift register used for shifting data in or out. SSPBUF is the buffer register to which data bytes are written to or read from. In receive operations, SSPSR and SSPBUF together create a double-buffered receiver. When SSPSR receives a complete byte, it is transferred to SSPBUF and the SSPIF interrupt is set. During transmission, the SSPBUF is not doublebuffered. A write to SSPBUF will write to both SSPBUF and SSPSR. REGISTER 19-1: SSPSTAT: MSSP STATUS REGISTER (SPI MODE) R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0 SMP CKE(1) D/A P S R/W UA BF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SMP: Sample bit SPI Master mode: 1 = Input data sampled at end of data output time 0 = Input data sampled at middle of data output time SPI Slave mode: SMP must be cleared when SPI is used in Slave mode. bit 6 CKE: SPI Clock Select bit(1) 1 = Transmit occurs on transition from active to Idle clock state 0 = Transmit occurs on transition from Idle to active clock state bit 5 D/A: Data/Address bit Used in I2C mode only. bit 4 P: Stop bit Used in I2C mode only. This bit is cleared when the MSSP module is disabled, SSPEN is cleared. bit 3 S: Start bit Used in I2C mode only. bit 2 R/W: Read/Write Information bit Used in I2C mode only. bit 1 UA: Update Address bit Used in I2C mode only. bit 0 BF: Buffer Full Status bit (Receive mode only) 1 = Receive complete, SSPBUF is full 0 = Receive not complete, SSPBUF is empty Note 1: Polarity of clock state is set by the CKP bit (SSPCON1<4>). © 2009 Microchip Technology Inc. DS39632E-page 199 PIC18F2455/2550/4455/4550 REGISTER 19-2: SSPCON1: MSSP CONTROL REGISTER 1 (SPI MODE) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 WCOL SSPOV(1) SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 WCOL: Write Collision Detect bit (Transmit mode only) 1 = The SSPBUF register is written while it is still transmitting the previous word (must be cleared in software) 0 = No collision bit 6 SSPOV: Receive Overflow Indicator bit(1) SPI Slave mode: 1 = A new byte is received while the SSPBUF register is still holding the previous data. In case of overflow, the data in SSPSR is lost. Overflow can only occur in Slave mode. The user must read the SSPBUF, even if only transmitting data, to avoid setting overflow (must be cleared in software). 0 = No overflow bit 5 SSPEN: Master Synchronous Serial Port Enable bit 1 = Enables serial port and configures SCK, SDO, SDI and SS as serial port pins(2) 0 = Disables serial port and configures these pins as I/O port pins(2) bit 4 CKP: Clock Polarity Select bit 1 = Idle state for clock is a high level 0 = Idle state for clock is a low level bit 3-0 SSPM3:SSPM0: Master Synchronous Serial Port Mode Select bits 0101 = SPI Slave mode, clock = SCK pin, SS pin control disabled, SS can be used as I/O pin(3) 0100 = SPI Slave mode, clock = SCK pin, SS pin control enabled(3) 0011 = SPI Master mode, clock = TMR2 output/2(3,4) 0010 = SPI Master mode, clock = FOSC/64(3) 0001 = SPI Master mode, clock = FOSC/16(3) 0000 = SPI Master mode, clock = FOSC/4(3) Note 1: In Master mode, the overflow bit is not set since each new reception (and transmission) is initiated by writing to the SSPBUF register. 2: When enabled, these pins must be properly configured as input or output. 3: Bit combinations not specifically listed here are either reserved or implemented in I2C™ mode only. 4: PR2 = 0x00 is not supported when running the SPI module in TMR2 Output/2 mode. PIC18F2455/2550/4455/4550 DS39632E-page 200 © 2009 Microchip Technology Inc. 19.3.2 OPERATION When initializing the SPI, several options need to be specified. This is done by programming the appropriate control bits (SSPCON1<5:0> and SSPSTAT<7:6>). These control bits allow the following to be specified: • Master mode (SCK is the clock output) • Slave mode (SCK is the clock input) • Clock Polarity (Idle state of SCK) • Data Input Sample Phase (middle or end of data output time) • Clock Edge (output data on rising/falling edge of SCK) • Clock Rate (Master mode only) • Slave Select mode (Slave mode only) The MSSP module consists of a transmit/receive shift register (SSPSR) and a buffer register (SSPBUF). The SSPSR shifts the data in and out of the device, MSb first. The SSPBUF holds the data that was written to the SSPSR until the received data is ready. Once the eight bits of data have been received, that byte is moved to the SSPBUF register. Then, the Buffer Full detect bit, BF (SSPSTAT<0>) and the interrupt flag bit, SSPIF, are set. This double-buffering of the received data (SSPBUF) allows the next byte to start reception before reading the data that was just received. Any write to the SSPBUF register during transmission/reception of data will be ignored and the Write Collision detect bit, WCOL (SSPCON1<7>), will be set. User software must clear the WCOL bit so that it can be determined if the following write(s) to the SSPBUF register completed successfully. The Buffer Full bit, BF (SSPSTAT<0>), indicates when SSPBUF has been loaded with the received data (transmission is complete). When the SSPBUF is read, the BF bit is cleared. This data may be irrelevant if the SPI is only a transmitter. Generally, the MSSP interrupt is used to determine when the transmission/reception has completed. If the interrupt method is not going to be used, then software polling can be done to ensure that a write collision does not occur. Example 19-1 shows the loading of the SSPBUF (SSPSR) for data transmission. The SSPSR is not directly readable or writable and can only be accessed by addressing the SSPBUF register. Additionally, the MSSP Status register (SSPSTAT) indicates the various status conditions. EXAMPLE 19-1: LOADING THE SSPBUF (SSPSR) REGISTER Note: When the application software is expecting to receive valid data, the SSPBUF should be read before the next byte of data to transfer is written to the SSPBUF. Application software should follow this process even when the current contents of SSPBUF are not important. Note: The SSPBUF register cannot be used with read-modify-write instructions, such as BCF, BTFSC and COMF. TransmitSPI: BCF PIR1, SSPIF ;Make sure interrupt flag is clear (may have been set from previous transmission). MOVF SSPBUF, W ;Perform read, even if the data in SSPBUF is not important MOVWF RXDATA ;Save previously received byte in user RAM, if the data is meaningful MOVF TXDATA, W ;WREG = Contents of TXDATA (user data to send) MOVWF SSPBUF ;Load data to send into transmit buffer WaitComplete: ;Loop until data has finished transmitting BTFSS PIR1, SSPIF ;Interrupt flag set when transmit is complete BRA WaitComplete © 2009 Microchip Technology Inc. DS39632E-page 201 PIC18F2455/2550/4455/4550 19.3.3 ENABLING SPI I/O To enable the serial port, MSSP Enable bit, SSPEN (SSPCON1<5>), must be set. To reset or reconfigure SPI mode, clear the SSPEN bit, reinitialize the SSPCON registers and then set the SSPEN bit. This configures the SDI, SDO, SCK and SS pins as serial port pins. For the pins to behave as the serial port function, some must have their data direction bits (in the TRIS register) appropriately programmed as follows: • SDI must have TRISB<0> bit set (configure as digital in ADCON1) • SDO must have TRISC<7> bit cleared • SCK (Master mode) must have TRISB<1> bit cleared • SCK (Slave mode) must have TRISB<1> bit set (configure as digital in ADCON1) • SS must have TRISA<5> bit set (configure as digital in ADCON1) Any serial port function that is not desired may be overridden by programming the corresponding data direction (TRIS) register to the opposite value. Input functions which will not be used do not need to be configured as digital inputs. 19.3.4 TYPICAL CONNECTION Figure 19-2 shows a typical connection between two microcontrollers. The master controller (Processor 1) initiates the data transfer by sending the SCK signal. Data is shifted out of both shift registers on their programmed clock edge and latched on the opposite edge of the clock. Both processors should be programmed to the same Clock Polarity (CKP), then both controllers would send and receive data at the same time. Whether the data is meaningful (or dummy data) depends on the application software. This leads to three scenarios for data transmission: • Master sends data – Slave sends dummy data • Master sends data – Slave sends data • Master sends dummy data – Slave sends data FIGURE 19-2: SPI MASTER/SLAVE CONNECTION Serial Input Buffer (SSPBUF) Shift Register (SSPSR) MSb LSb SDO SDI PROCESSOR 1 SCK SPI Master SSPM3:SSPM0 = 00xxb Serial Input Buffer (SSPBUF) Shift Register (SSPSR) MSb LSb SDI SDO PROCESSOR 2 SCK SPI Slave SSPM3:SSPM0 = 010xb Serial Clock PIC18F2455/2550/4455/4550 DS39632E-page 202 © 2009 Microchip Technology Inc. 19.3.5 MASTER MODE The master can initiate the data transfer at any time because it controls the SCK. The master determines when the slave (Processor 2, Figure 19-2) is to broadcast data by the software protocol. In Master mode, the data is transmitted/received as soon as the SSPBUF register is written to. If the SPI is only going to receive, the SDO output could be disabled (programmed as an input). The SSPSR register will continue to shift in the signal present on the SDI pin at the programmed clock rate. As each byte is received, it will be loaded into the SSPBUF register as if a normal received byte (interrupts and status bits appropriately set). This could be useful in receiver applications as a “Line Activity Monitor” mode. The clock polarity is selected by appropriately programming the CKP bit (SSPCON1<4>). This, then, would give waveforms for SPI communication as shown in Figure 19-3, Figure 19-5 and Figure 19-6, where the MSB is transmitted first. In Master mode, the SPI clock rate (bit rate) is user-programmable to be one of the following: • FOSC/4 (or TCY) • FOSC/16 (or 4 • TCY) • FOSC/64 (or 16 • TCY) • Timer2 output/2 This allows a maximum data rate (at 48 MHz) of 12.00 Mbps. When used in Timer2 Output/2 mode, the bit rate can be configured using the PR2 Period register and the Timer2 prescaler. However, writing to SSPBUF does not clear the current TMR2 value in hardware. Depending upon the current value of TMR2 when the user firmware writes to SSPBUF, this can result in an unpredictable MSb bit width, unless the procedure of Example 19-2 is used. Figure 19-3 shows the waveforms for Master mode. When the CKE bit is set, the SDO data is valid before there is a clock edge on SCK. The change of the input sample is shown based on the state of the SMP bit. The time when the SSPBUF is loaded with the received data is shown. EXAMPLE 19-2: LOADING SSPBUF WITH THE TIMER2/2 CLOCK MODE TransmitSPI: BCF PIR1, SSPIF ;Make sure interrupt flag is clear (may have been set from previous transmission) MOVF SSPBUF, W ;Perform read, even if the data in SSPBUF is not important MOVWF RXDATA ;Save previously received byte in user RAM, if the data is meaningful BCF T2CON, TMR2ON ;Turn off timer when loading SSPBUF CLRF TMR2 ;Set timer to a known state MOVF TXDATA, W ;WREG = Contents of TXDATA (user data to send) MOVWF SSPBUF ;Load data to send into transmit buffer BSF T2CON, TMR2ON ;Start timer to begin transmission WaitComplete: ;Loop until data has finished transmitting BTFSS PIR1, SSPIF ;Interrupt flag set when transmit is complete BRA WaitComplete © 2009 Microchip Technology Inc. DS39632E-page 203 PIC18F2455/2550/4455/4550 FIGURE 19-3: SPI MODE WAVEFORM (MASTER MODE) SCK (CKP = 0 SCK (CKP = 1 SCK (CKP = 0 SCK (CKP = 1 4 Clock Modes Input Sample Input Sample SDI bit 7 bit 0 SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 bit 7 SDI SSPIF (SMP = 1) (SMP = 0) (SMP = 1) CKE = 1) CKE = 0) CKE = 1) CKE = 0) (SMP = 0) Write to SSPBUF SSPSR to SSPBUF SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (CKE = 0) (CKE = 1) Next Q4 Cycle after Q2↓ bit 0 PIC18F2455/2550/4455/4550 DS39632E-page 204 © 2009 Microchip Technology Inc. 19.3.6 SLAVE MODE In Slave mode, the data is transmitted and received as the external clock pulses appear on SCK. When the last bit is latched, the SSPIF interrupt flag bit is set. While in Slave mode, the external clock is supplied by the external clock source on the SCK pin. This external clock must meet the minimum high and low times as specified in the electrical specifications. While in Sleep mode, the slave can transmit/receive data. When a byte is received, the device can be configured to wake-up from Sleep. 19.3.7 SLAVE SELECT SYNCHRONIZATION The SS pin allows a Synchronous Slave mode. The SPI must be in Slave mode with the SS pin control enabled (SSPCON1<3:0> = 04h). When the SS pin is low, transmission and reception are enabled and the SDO pin is driven. When the SS pin goes high, the SDO pin is no longer driven, even if in the middle of a transmitted byte and becomes a floating output. External pull-up/pull-down resistors may be desirable depending on the application. When the SPI module resets, the bit counter is forced to ‘0’. This can be done by either forcing the SS pin to a high level or clearing the SSPEN bit. To emulate two-wire communication, the SDO pin can be connected to the SDI pin. When the SPI needs to operate as a receiver, the SDO pin can be configured as an input. This disables transmissions from the SDO. The SDI can always be left as an input (SDI function) since it cannot create a bus conflict. FIGURE 19-4: SLAVE SYNCHRONIZATION WAVEFORM Note 1: When the SPI module is in Slave mode with SS pin control enabled (SSPCON1<3:0> = 0100), the SPI module will reset if the SS pin is set to VDD. 2: If the SPI is used in Slave mode with CKE set, then the SS pin control must be enabled. SCK (CKP = 1 SCK (CKP = 0 Input Sample SDI bit 7 SDO bit 7 bit 6 bit 7 SSPIF Interrupt (SMP = 0) CKE = 0) CKE = 0) (SMP = 0) Write to SSPBUF SSPSR to SSPBUF SS Flag bit 0 bit 7 bit 0 Next Q4 Cycle after Q2↓ © 2009 Microchip Technology Inc. DS39632E-page 205 PIC18F2455/2550/4455/4550 FIGURE 19-5: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 0) FIGURE 19-6: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 1) SCK (CKP = 1 SCK (CKP = 0 Input Sample SDI bit 7 SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 SSPIF Interrupt (SMP = 0) CKE = 0) CKE = 0) (SMP = 0) Write to SSPBUF SSPSR to SSPBUF SS Flag Optional Next Q4 Cycle after Q2↓ bit 0 SCK (CKP = 1 SCK (CKP = 0 Input Sample SDI bit 7 bit 0 SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 SSPIF Interrupt (SMP = 0) CKE = 1) CKE = 1) (SMP = 0) Write to SSPBUF SSPSR to SSPBUF SS Flag Not Optional Next Q4 Cycle after Q2↓ PIC18F2455/2550/4455/4550 DS39632E-page 206 © 2009 Microchip Technology Inc. 19.3.8 OPERATION IN POWER-MANAGED MODES In SPI Master mode, module clocks may be operating at a different speed than when in Full-Power mode; in the case of the Sleep mode, all clocks are halted. In most Idle modes, a clock is provided to the peripherals. That clock should be from the primary clock source, the secondary clock (Timer1 oscillator) or the INTOSC source. See Section 2.4 “Clock Sources and Oscillator Switching” for additional information. In most cases, the speed that the master clocks SPI data is not important; however, this should be evaluated for each system. If MSSP interrupts are enabled, they can wake the controller from Sleep mode or one of the Idle modes when the master completes sending data. If an exit from Sleep or Idle mode is not desired, MSSP interrupts should be disabled. If the Sleep mode is selected, all module clocks are halted and the transmission/reception will remain in that state until the devices wakes. After the device returns to Run mode, the module will resume transmitting and receiving data. In SPI Slave mode, the SPI Transmit/Receive Shift register operates asynchronously to the device. This allows the device to be placed in any power-managed mode and data to be shifted into the SPI Transmit/ Receive Shift register. When all eight bits have been received, the MSSP interrupt flag bit will be set and if enabled, will wake the device. 19.3.9 EFFECTS OF A RESET A Reset disables the MSSP module and terminates the current transfer. 19.3.10 BUS MODE COMPATIBILITY Table 19-1 shows the compatibility between the standard SPI modes and the states of the CKP and CKE control bits. TABLE 19-1: SPI BUS MODES There is also an SMP bit which controls when the data is sampled. TABLE 19-2: REGISTERS ASSOCIATED WITH SPI OPERATION Standard SPI Mode Terminology Control Bits State CKP CKE 0, 0 0 1 0, 1 0 0 1, 0 1 1 1, 1 1 0 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 TRISA — TRISA6(2) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 SSPBUF MSSP Receive Buffer/Transmit Register 54 SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 54 SSPSTAT SMP CKE D/A P S R/W UA BF 54 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the MSSP in SPI mode. Note 1: These bits are unimplemented in 28-pin devices; always maintain these bits clear. 2: RA6 is configured as a port pin based on various primary oscillator modes. When the port pin is disabled, all of the associated bits read ‘0’. © 2009 Microchip Technology Inc. DS39632E-page 207 PIC18F2455/2550/4455/4550 19.4 I2C Mode The MSSP module in I2C mode fully implements all master and slave functions (including general call support) and provides interrupts on Start and Stop bits in hardware to determine a free bus (multi-master function). The MSSP module implements the standard mode specifications, as well as 7-bit and 10-bit addressing. Two pins are used for data transfer: • Serial clock (SCL) – RB1/AN10/INT1/SCK/SCL • Serial data (SDA) – RB0/AN12/INT0/FLT0/SDI/SDA The user must configure these pins as inputs by setting the associated TRIS bits. FIGURE 19-7: MSSP BLOCK DIAGRAM (I2C™ MODE) 19.4.1 REGISTERS The MSSP module has six registers for I2C operation. These are: • MSSP Control Register 1 (SSPCON1) • MSSP Control Register 2 (SSPCON2) • MSSP Status Register (SSPSTAT) • Serial Receive/Transmit Buffer Register (SSPBUF) • MSSP Shift Register (SSPSR) – Not directly accessible • MSSP Address Register (SSPADD) SSPCON1, SSPCON2 and SSPSTAT are the control and status registers in I2C mode operation. The SSPCON1 and SSPCON2 registers are readable and writable. The lower six bits of the SSPSTAT are read-only. The upper two bits of the SSPSTAT are read/write. SSPSR is the shift register used for shifting data in or out. SSPBUF is the buffer register to which data bytes are written to or read from. SSPADD register holds the slave device address when the MSSP is configured in I2C Slave mode. When the MSSP is configured in Master mode, the lower seven bits of SSPADD act as the Baud Rate Generator reload value. In receive operations, SSPSR and SSPBUF together create a double-buffered receiver. When SSPSR receives a complete byte, it is transferred to SSPBUF and the SSPIF interrupt is set. During transmission, the SSPBUF is not doublebuffered. A write to SSPBUF will write to both SSPBUF and SSPSR. Read Write SSPSR reg Match Detect SSPADD reg SSPBUF reg Internal Data Bus Addr Match Set, Reset S, P bits (SSPSTAT reg) Shift Clock MSb LSb Note: Only port I/O names are used in this diagram for the sake of brevity. Refer to the text for a full list of multiplexed functions. SCL SDA Start and Stop bit Detect Address Mask PIC18F2455/2550/4455/4550 DS39632E-page 208 © 2009 Microchip Technology Inc. REGISTER 19-3: SSPSTAT: MSSP STATUS REGISTER (I2C™ MODE) R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0 SMP CKE D/A P(1) S(1) R/W(2,3) UA BF bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SMP: Slew Rate Control bit In Master or Slave mode: 1 = Slew rate control disabled for Standard Speed mode (100 kHz and 1 MHz) 0 = Slew rate control enabled for High-Speed mode (400 kHz) bit 6 CKE: SMBus Select bit In Master or Slave mode: 1 = Enable SMBus specific inputs 0 = Disable SMBus specific inputs bit 5 D/A: Data/Address bit In Master mode: Reserved. In Slave mode: 1 = Indicates that the last byte received or transmitted was data 0 = Indicates that the last byte received or transmitted was address bit 4 P: Stop bit(1) 1 = Indicates that a Stop bit has been detected last 0 = Stop bit was not detected last bit 3 S: Start bit(1) 1 = Indicates that a Start bit has been detected last 0 = Start bit was not detected last bit 2 R/W: Read/Write Information bit(2,3) In Slave mode: 1 = Read 0 = Write In Master mode: 1 = Transmit is in progress 0 = Transmit is not in progress bit 1 UA: Update Address bit (10-Bit Slave mode only) 1 = Indicates that the user needs to update the address in the SSPADD register 0 = Address does not need to be updated bit 0 BF: Buffer Full Status bit In Transmit mode: 1 = SSPBUF is full 0 = SSPBUF is empty In Receive mode: 1 = SSPBUF is full (does not include the ACK and Stop bits) 0 = SSPBUF is empty (does not include the ACK and Stop bits) Note 1: This bit is cleared on Reset and when SSPEN is cleared. 2: This bit holds the R/W bit information following the last address match. This bit is only valid from the address match to the next Start bit, Stop bit or not ACK bit. 3: ORing this bit with SEN, RSEN, PEN, RCEN or ACKEN will indicate if the MSSP is in Active mode. © 2009 Microchip Technology Inc. DS39632E-page 209 PIC18F2455/2550/4455/4550 REGISTER 19-4: SSPCON1: MSSP CONTROL REGISTER 1 (I2C™ MODE) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 WCOL: Write Collision Detect bit In Master Transmit mode: 1 = A write to the SSPBUF register was attempted while the I2C conditions were not valid for a transmission to be started (must be cleared in software) 0 = No collision In Slave Transmit mode: 1 = The SSPBUF register is written while it is still transmitting the previous word (must be cleared in software) 0 = No collision In Receive mode (Master or Slave modes): This is a “don’t care” bit. bit 6 SSPOV: Receive Overflow Indicator bit In Receive mode: 1 = A byte is received while the SSPBUF register is still holding the previous byte (must be cleared in software) 0 = No overflow In Transmit mode: This is a “don’t care” bit in Transmit mode. bit 5 SSPEN: Master Synchronous Serial Port Enable bit 1 = Enables the serial port and configures the SDA and SCL pins as the serial port pins(1) 0 = Disables serial port and configures these pins as I/O port pins(1) bit 4 CKP: SCK Release Control bit In Slave mode: 1 = Release clock 0 = Holds clock low (clock stretch), used to ensure data setup time In Master mode: Unused in this mode. bit 3-0 SSPM3:SSPM0: Master Synchronous Serial Port Mode Select bits 1111 = I2C Slave mode, 10-bit address with Start and Stop bit interrupts enabled(2) 1110 = I2C Slave mode, 7-bit address with Start and Stop bit interrupts enabled(2) 1011 = I2C Firmware Controlled Master mode (slave Idle)(2) 1000 = I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))(2,3) 0111 = I2C Slave mode, 10-bit address(2) 0110 = I2C Slave mode, 7-bit address(2) Note 1: When enabled, the SDA and SCL pins must be properly configured as input or output. 2: Bit combinations not specifically listed here are either reserved or implemented in SPI mode only. 3: Guideline only; exact baud rate slightly dependent upon circuit conditions, but the highest clock rate should not exceed this formula. SSPADD values of ‘0’ and ‘1’ are not supported. PIC18F2455/2550/4455/4550 DS39632E-page 210 © 2009 Microchip Technology Inc. REGISTER 19-5: SSPCON2: MSSP CONTROL REGISTER 2 (I2C™ MASTER MODE) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 GCEN ACKSTAT ACKDT(1) ACKEN(2) RCEN(2) PEN(2) RSEN(2) SEN(2) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 GCEN: General Call Enable bit (Slave mode only) Unused in Master mode. bit 6 ACKSTAT: Acknowledge Status bit (Master Transmit mode only) 1 = Acknowledge was not received from slave 0 = Acknowledge was received from slave bit 5 ACKDT: Acknowledge Data bit (Master Receive mode only)(1) 1 = Not Acknowledge 0 = Acknowledge bit 4 ACKEN: Acknowledge Sequence Enable bit(2) 1 = Initiate Acknowledge sequence on SDA and SCL pins and transmit ACKDT data bit. Automatically cleared by hardware. 0 = Acknowledge sequence Idle bit 3 RCEN: Receive Enable bit (Master Receive mode only)(2) 1 = Enables Receive mode for I2C 0 = Receive Idle bit 2 PEN: Stop Condition Enable bit(2) 1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware. 0 = Stop condition Idle bit 1 RSEN: Repeated Start Condition Enable bit(2) 1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware. 0 = Repeated Start condition Idle bit 0 SEN: Start Condition Enable/Stretch Enable bit(2) 1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware. 0 = Start condition Idle Note 1: Value that will be transmitted when the user initiates an Acknowledge sequence at the end of a receive. 2: If the I2C module is active, these bits may not be set (no spooling) and the SSPBUF may not be written (or writes to the SSPBUF are disabled). © 2009 Microchip Technology Inc. DS39632E-page 211 PIC18F2455/2550/4455/4550 REGISTER 19-6: SSPCON2: MSSP CONTROL REGISTER 2 (I2C™ SLAVE MODE) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 GCEN ACKSTAT ADMSK5 ADMSK4 ADMSK3 ADMSK2 ADMSK1 SEN(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 GCEN: General Call Enable bit (Slave mode only) 1 = Enable interrupt when a general call address (0000h) is received in the SSPSR 0 = General call address disabled bit 6 ACKSTAT: Acknowledge Status bit Unused in Slave mode. bit 5-2 ADMSK5:ADMSK2: Slave Address Mask Select bits 1 = Masking of corresponding bits of SSPADD enabled 0 = Masking of corresponding bits of SSPADD disabled bit 1 ADMSK1: Slave Address Mask Select bit In 7-Bit Addressing mode: 1 = Masking of SPADD<1> only enabled 0 = Masking of SPADD<1> only disabled In 10-Bit Addressing mode: 1 = Masking of SSPADD<1:0> enabled 0 = Masking of SSPADD<1:0> disabled bit 0 SEN: Stretch Enable bit(1) 1 = Clock stretching is enabled for both slave transmit and slave receive (stretch enabled) 0 = Clock stretching is disabled Note 1: If the I2C module is active, this bit may not be set (no spooling) and the SSPBUF may not be written (or writes to the SSPBUF are disabled). PIC18F2455/2550/4455/4550 DS39632E-page 212 © 2009 Microchip Technology Inc. 19.4.2 OPERATION The MSSP module functions are enabled by setting MSSP Enable bit, SSPEN (SSPCON1<5>). The SSPCON1 register allows control of the I2C operation. Four mode selection bits (SSPCON1<3:0>) allow one of the following I2C modes to be selected: • I2C Master mode, clock • I2C Slave mode (7-bit address) • I2C Slave mode (10-bit address) • I2C Slave mode (7-bit address) with Start and Stop bit interrupts enabled • I2C Slave mode (10-bit address) with Start and Stop bit interrupts enabled • I2C Firmware Controlled Master mode, slave is Idle Selection of any I2C mode with the SSPEN bit set forces the SCL and SDA pins to be open-drain, provided these pins are programmed as inputs by setting the appropriate TRISC or TRISD bits. To ensure proper operation of the module, pull-up resistors must be provided externally to the SCL and SDA pins. 19.4.3 SLAVE MODE In Slave mode, the SCL and SDA pins must be configured as inputs (TRISC<4:3> set). The MSSP module will override the input state with the output data when required (slave-transmitter). The I2C Slave mode hardware will always generate an interrupt on an address match. Address masking will allow the hardware to generate an interrupt for more than one address (up to 31 in 7-bit addressing and up to 63 in 10-bit addressing). Through the mode select bits, the user can also choose to interrupt on Start and Stop bits. When an address is matched, or the data transfer after an address match is received, the hardware automatically will generate the Acknowledge (ACK) pulse and load the SSPBUF register with the received value currently in the SSPSR register. Any combination of the following conditions will cause the MSSP module not to give this ACK pulse: • The Buffer Full bit, BF (SSPSTAT<0>), was set before the transfer was received. • The overflow bit, SSPOV (SSPCON1<6>), was set before the transfer was received. In this case, the SSPSR register value is not loaded into the SSPBUF, but bit, SSPIF, is set. The BF bit is cleared by reading the SSPBUF register, while bit, SSPOV, is cleared through software. The SCL clock input must have a minimum high and low for proper operation. The high and low times of the I2C specification, as well as the requirement of the MSSP module, are shown in timing parameter 100 and parameter 101. 19.4.3.1 Addressing Once the MSSP module has been enabled, it waits for a Start condition to occur. Following the Start condition, the 8 bits are shifted into the SSPSR register. All incoming bits are sampled with the rising edge of the clock (SCL) line. The value of register SSPSR<7:1> is compared to the value of the SSPADD register. The address is compared on the falling edge of the eighth clock (SCL) pulse. If the addresses match and the BF and SSPOV bits are clear, the following events occur: 1. The SSPSR register value is loaded into the SSPBUF register. 2. The Buffer Full bit, BF, is set. 3. An ACK pulse is generated. 4. The MSSP Interrupt Flag bit, SSPIF, is set (and interrupt is generated, if enabled) on the falling edge of the ninth SCL pulse. In 10-Bit Addressing mode, two address bytes need to be received by the slave. The five Most Significant bits (MSbs) of the first address byte specify if this is a 10-bit address. Bit R/W (SSPSTAT<2>) must specify a write so the slave device will receive the second address byte. For a 10-bit address, the first byte would equal ‘11110 A9 A8 0’, where ‘A9’ and ‘A8’ are the two MSbs of the address. The sequence of events for 10-bit addressing is as follows, with steps 7 through 9 for the slave-transmitter: 1. Receive first (high) byte of address (bits SSPIF, BF and UA (SSPSTAT<1>) are set on address match). 2. Update the SSPADD register with second (low) byte of address (clears bit, UA, and releases the SCL line). 3. Read the SSPBUF register (clears bit, BF) and clear flag bit, SSPIF. 4. Receive second (low) byte of address (bits, SSPIF, BF and UA, are set). 5. Update the SSPADD register with the first (high) byte of address. If match releases SCL line, this will clear bit, UA. 6. Read the SSPBUF register (clears bit, BF) and clear flag bit, SSPIF. 7. Receive Repeated Start condition. 8. Receive first (high) byte of address (bits, SSPIF and BF, are set). 9. Read the SSPBUF register (clears bit, BF) and clear flag bit, SSPIF. © 2009 Microchip Technology Inc. DS39632E-page 213 PIC18F2455/2550/4455/4550 19.4.3.2 Address Masking Masking an address bit causes that bit to become a “don’t care”. When one address bit is masked, two addresses will be Acknowledged and cause an interrupt. It is possible to mask more than one address bit at a time, which makes it possible to Acknowledge up to 31 addresses in 7-bit mode and up to 63 addresses in 10-bit mode (see Example 19-3). The I2C Slave behaves the same way whether address masking is used or not. However, when address masking is used, the I2C slave can Acknowledge multiple addresses and cause interrupts. When this occurs, it is necessary to determine which address caused the interrupt by checking SSPBUF. In 7-Bit Address mode, address mask bits ADMSK<5:1> (SSPCON2<5:1>) mask the corresponding address bits in the SSPADD register. For any ADMSK bits that are set (ADMSK = 1), the corresponding address bit is ignored (SSPADD = x). For the module to issue an address Acknowledge, it is sufficient to match only on addresses that do not have an active address mask. In 10-Bit Address mode, bits ADMSK<5:2> mask the corresponding address bits in the SSPADD register. In addition, ADMSK1 simultaneously masks the two LSbs of the address (SSPADD<1:0>). For any ADMSK bits that are active (ADMSK = 1), the corresponding address bit is ignored (SSPADD = x). Also note that although in 10-Bit Addressing mode, the upper address bits reuse part of the SSPADD register bits, the address mask bits do not interact with those bits. They only affect the lower address bits. EXAMPLE 19-3: ADDRESS MASKING EXAMPLES Note 1: ADMSK1 masks the two Least Significant bits of the address. 2: The two Most Significant bits of the address are not affected by address masking. 7-bit addressing: SSPADD<7:1> = A0h (1010000) (SSPADD<0> is assumed to be ‘0’) ADMSK<5:1> = 00111 Addresses Acknowledged : A0h, A2h, A4h, A6h, A8h, AAh, ACh, AEh 10-bit addressing: SSPADD<7:0> = A0h (10100000) (The two MSbs of the address are ignored in this example, since they are not affected by masking) ADMSK<5:1> = 00111 Addresses Acknowledged: A0h, A1h, A2h, A3h, A4h, A5h, A6h, A7h, A8h, A9h, AAh, ABh, ACh, ADh, AEh, AFh PIC18F2455/2550/4455/4550 DS39632E-page 214 © 2009 Microchip Technology Inc. 19.4.3.3 Reception When the R/W bit of the address byte is clear and an address match occurs, the R/W bit of the SSPSTAT register is cleared. The received address is loaded into the SSPBUF register and the SDA line is held low (ACK). When the address byte overflow condition exists, then the no Acknowledge (ACK) pulse is given. An overflow condition is defined as either bit, BF (SSPSTAT<0>), is set, or bit, SSPOV (SSPCON1<6>), is set. An MSSP interrupt is generated for each data transfer byte. The Interrupt Flag bit, SSPIF, must be cleared in software. The SSPSTAT register is used to determine the status of the byte. If SEN is enabled (SSPCON2<0> = 1), RB1/AN10/ INT1/SCK/SCL will be held low (clock stretch) following each data transfer. The clock must be released by setting bit, CKP (SSPCON1<4>). See Section 19.4.4 “Clock Stretching” for more detail. 19.4.3.4 Transmission When the R/W bit of the incoming address byte is set and an address match occurs, the R/W bit of the SSPSTAT register is set. The received address is loaded into the SSPBUF register. The ACK pulse will be sent on the ninth bit and pin RB1/AN10/INT1/SCK/ SCL is held low regardless of SEN (see Section 19.4.4 “Clock Stretching” for more detail). By stretching the clock, the master will be unable to assert another clock pulse until the slave is done preparing the transmit data. The transmit data must be loaded into the SSPBUF register which also loads the SSPSR register. Then the RB1/AN10/INT1/SCK/SCL pin should be enabled by setting bit, CKP (SSPCON1<4>). The eight data bits are shifted out on the falling edge of the SCL input. This ensures that the SDA signal is valid during the SCL high time (Figure 19-10). The ACK pulse from the master-receiver is latched on the rising edge of the ninth SCL input pulse. If the SDA line is high (not ACK), then the data transfer is complete. In this case, when the ACK is latched by the slave, the slave logic is reset (resets SSPSTAT register) and the slave monitors for another occurrence of the Start bit. If the SDA line was low (ACK), the next transmit data must be loaded into the SSPBUF register. Again, the RB1/AN10/INT1/SCK/SCL pin must be enabled by setting bit CKP (SSPCON1<4>). An MSSP interrupt is generated for each data transfer byte. The SSPIF bit must be cleared in software and the SSPSTAT register is used to determine the status of the byte. The SSPIF bit is set on the falling edge of the ninth clock pulse. © 2009 Microchip Technology Inc. DS39632E-page 215 PIC18F2455/2550/4455/4550 FIGURE 19-8: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 7-BIT ADDRESS) SDA SCL SSPIF BF (SSPSTAT<0>) SSPOV (SSPCON1<6>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0 R/W = 0 Receiving Data ACK Receiving Data ACK ACK Receiving Address Cleared in software SSPBUF is read Bus master terminates transfer SSPOV is set because SSPBUF is still full. ACK is not sent. D2 6 (PIR1<3>) CKP (CKP does not reset to ‘0’ when SEN = 0) PIC18F2455/2550/4455/4550 DS39632E-page 216 © 2009 Microchip Technology Inc. FIGURE 19-9: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK<5:1> = 01011 (RECEPTION, 7-BIT ADDRESS) SDA SCL SSPIF (PIR1<3>) BF (SSPSTAT<0>) SSPOV (SSPCON1<6>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P A7 A6 A5 X A3 X X D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0 R/W = 0 Receiving Data ACK Receiving Data ACK ACK Receiving Address Cleared in software SSPBUF is read Bus master terminates transfer SSPOV is set because SSPBUF is still full. ACK is not sent. D2 6 CKP (CKP does not reset to ‘0’ when SEN = 0) Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’). 2: In this example, an address equal to A7.A6.A5.X.A3.X.X will be Acknowledged and cause an interrupt. © 2009 Microchip Technology Inc. DS39632E-page 217 PIC18F2455/2550/4455/4550 FIGURE 19-10: I2C™ SLAVE MODE TIMING (TRANSMISSION, 7-BIT ADDRESS) SDA SCL SSPIF (PIR1<3>) BF (SSPSTAT<0>) A6 A5 A4 A3 A2 A1 D6 D5 D4 D3 D2 D1 D0 1 2 3 4 5 6 7 8 2 3 4 5 6 7 8 9 SSPBUF is written in software Cleared in software Data in sampled S ACK R/W = 1 Transmitting Data ACK Receiving Address A7 D7 9 1 D6 D5 D4 D3 D2 D1 D0 2 3 4 5 6 7 8 9 SSPBUF is written in software Cleared in software From SSPIF ISR Transmitting Data D7 1 CKP P ACK CKP is set in software CKP is set in software From SSPIF ISR SCL held low while CPU responds to SSPIF PIC18F2455/2550/4455/4550 DS39632E-page 218 © 2009 Microchip Technology Inc. FIGURE 19-11: I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 10-BIT ADDRESS) SDA SCL SSPIF BF (SSPSTAT<0>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P 1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D1 D0 Receive Data Byte ACK R/W = 0 ACK Receive First Byte of Address Cleared in software D2 6 (PIR1<3>) Cleared in software Receive Second Byte of Address Cleared by hardware when SSPADD is updated with low byte of address UA (SSPSTAT<1>) Clock is held low until update of SSPADD has taken place UA is set indicating that the SSPADD needs to be updated UA is set indicating that SSPADD needs to be updated Cleared by hardware when SSPADD is updated with high byte of address SSPBUF is written with contents of SSPSR Dummy read of SSPBUF to clear BF flag ACK CKP 1 2 3 4 5 7 8 9 D7 D6 D5 D4 D3 D1 D0 Receive Data Byte Bus master terminates transfer D2 6 ACK Cleared in software Cleared in software SSPOV (SSPCON1<6>) SSPOV is set because SSPBUF is still full. ACK is not sent. (CKP does not reset to ‘0’ when SEN = 0) Clock is held low until update of SSPADD has taken place © 2009 Microchip Technology Inc. DS39632E-page 219 PIC18F2455/2550/4455/4550 FIGURE 19-12: I2C™ SLAVE MODE TIMING WITH SEN = 0 AND ADMSK<5:1> = 01001 (RECEPTION, 10-BIT ADDRESS) SDA SCL SSPIF (PIR1<3>) BF (SSPSTAT<0>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P 1 1 1 1 0 A9 A8 A7 A6 A5 X A3 A2 X X D7 D6 D5 D4 D3 D1 D0 Receive Data Byte ACK R/W = 0 ACK Receive First Byte of Address Cleared in software D2 6 Cleared in software Receive Second Byte of Address Cleared by hardware when SSPADD is updated with low byte of address UA (SSPSTAT<1>) Clock is held low until update of SSPADD has taken place UA is set indicating that the SSPADD needs to be updated UA is set indicating that SSPADD needs to be updated Cleared by hardware when SSPADD is updated with high byte of address SSPBUF is written with contents of SSPSR Dummy read of SSPBUF to clear BF flag ACK CKP 1 2 3 4 5 7 8 9 D7 D6 D5 D4 D3 D1 D0 Receive Data Byte Bus master terminates transfer D2 6 ACK Cleared in software Cleared in software SSPOV (SSPCON1<6>) SSPOV is set because SSPBUF is still full. ACK is not sent. (CKP does not reset to ‘0’ when SEN = 0) Clock is held low until update of SSPADD has taken place Note 1: x = Don’t care (i.e., address bit can be either a ‘1’ or a ‘0’). 2: In this example, an address equal to A9.A8.A7.A6.A5.X.A3.A2.X.X will be Acknowledged and cause an interrupt. 3: Note that the Most Significant bits of the address are not affected by the bit masking. PIC18F2455/2550/4455/4550 DS39632E-page 220 © 2009 Microchip Technology Inc. FIGURE 19-13: I2C™ SLAVE MODE TIMING (TRANSMISSION, 10-BIT ADDRESS) SDA SCL SSPIF BF (SSPSTAT<0>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P 1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 1 1 1 1 0 A8 R/W = 1 ACK ACK R/W = 0 ACK Receive First Byte of Address Cleared in software Bus master terminates transfer A9 6 (PIR1<3>) Receive Second Byte of Address Cleared by hardware when SSPADD is updated with low byte of address UA (SSPSTAT<1>) Clock is held low until update of SSPADD has taken place UA is set indicating that the SSPADD needs to be updated UA is set indicating that SSPADD needs to be updated Cleared by hardware when SSPADD is updated with high byte of address. SSPBUF is written with contents of SSPSR Dummy read of SSPBUF to clear BF flag Receive First Byte of Address 1 2 3 4 5 7 8 9 D7 D6 D5 D4 D3 D1 ACK D2 6 Transmitting Data Byte D0 Dummy read of SSPBUF to clear BF flag Sr Cleared in software Write of SSPBUF initiates transmit Cleared in software Completion of clears BF flag CKP (SSPCON1<4>) CKP is set in software CKP is automatically cleared in hardware, holding SCL low Clock is held low until update of SSPADD has taken place data transmission Clock is held low until CKP is set to ‘1’ third address sequence BF flag is clear at the end of the © 2009 Microchip Technology Inc. DS39632E-page 221 PIC18F2455/2550/4455/4550 19.4.4 CLOCK STRETCHING Both 7-Bit and 10-Bit Slave modes implement automatic clock stretching during a transmit sequence. The SEN bit (SSPCON2<0>) allows clock stretching to be enabled during receives. Setting SEN will cause the SCL pin to be held low at the end of each data receive sequence. 19.4.4.1 Clock Stretching for 7-Bit Slave Receive Mode (SEN = 1) In 7-Bit Slave Receive mode, on the falling edge of the ninth clock at the end of the ACK sequence if the BF bit is set, the CKP bit in the SSPCON1 register is automatically cleared, forcing the SCL output to be held low. The CKP bit being cleared to ‘0’ will assert the SCL line low. The CKP bit must be set in the user’s ISR before reception is allowed to continue. By holding the SCL line low, the user has time to service the ISR and read the contents of the SSPBUF before the master device can initiate another receive sequence. This will prevent buffer overruns from occurring (see Figure 19-15). 19.4.4.2 Clock Stretching for 10-Bit Slave Receive Mode (SEN = 1) In 10-Bit Slave Receive mode during the address sequence, clock stretching automatically takes place but CKP is not cleared. During this time, if the UA bit is set after the ninth clock, clock stretching is initiated. The UA bit is set after receiving the upper byte of the 10-bit address and following the receive of the second byte of the 10-bit address with the R/W bit cleared to ‘0’. The release of the clock line occurs upon updating SSPADD. Clock stretching will occur on each data receive sequence as described in 7-bit mode. 19.4.4.3 Clock Stretching for 7-Bit Slave Transmit Mode 7-Bit Slave Transmit mode implements clock stretching by clearing the CKP bit after the falling edge of the ninth clock if the BF bit is clear. This occurs regardless of the state of the SEN bit. The user’s ISR must set the CKP bit before transmission is allowed to continue. By holding the SCL line low, the user has time to service the ISR and load the contents of the SSPBUF before the master device can initiate another transmit sequence (see Figure 19-10). 19.4.4.4 Clock Stretching for 10-Bit Slave Transmit Mode In 10-Bit Slave Transmit mode, clock stretching is controlled during the first two address sequences by the state of the UA bit, just as it is in 10-Bit Slave Receive mode. The first two addresses are followed by a third address sequence which contains the highorder bits of the 10-bit address and the R/W bit set to ‘1’. After the third address sequence is performed, the UA bit is not set, the module is now configured in Transmit mode and clock stretching is controlled by the BF flag as in 7-Bit Slave Transmit mode (see Figure 19-13). Note 1: If the user reads the contents of the SSPBUF before the falling edge of the ninth clock, thus clearing the BF bit, the CKP bit will not be cleared and clock stretching will not occur. 2: The CKP bit can be set in software regardless of the state of the BF bit. The user should be careful to clear the BF bit in the ISR before the next receive sequence in order to prevent an overflow condition. Note: If the user polls the UA bit and clears it by updating the SSPADD register before the falling edge of the ninth clock occurs and if the user hasn’t cleared the BF bit by reading the SSPBUF register before that time, then the CKP bit will still NOT be asserted low. Clock stretching on the basis of the state of the BF bit only occurs during a data sequence, not an address sequence. Note 1: If the user loads the contents of SSPBUF, setting the BF bit before the falling edge of the ninth clock, the CKP bit will not be cleared and clock stretching will not occur. 2: The CKP bit can be set in software regardless of the state of the BF bit. PIC18F2455/2550/4455/4550 DS39632E-page 222 © 2009 Microchip Technology Inc. 19.4.4.5 Clock Synchronization and the CKP bit When the CKP bit is cleared, the SCL output is forced to ‘0’. However, clearing the CKP bit will not assert the SCL output low until the SCL output is already sampled low. Therefore, the CKP bit will not assert the SCL line until an external I2C master device has already asserted the SCL line. The SCL output will remain low until the CKP bit is set and all other devices on the I2C bus have deasserted SCL. This ensures that a write to the CKP bit will not violate the minimum high time requirement for SCL (see Figure 19-14). FIGURE 19-14: CLOCK SYNCHRONIZATION TIMING SDA SCL DX DX – 1 Write Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 SSPCON1 CKP Master device deasserts clock Master device asserts clock © 2009 Microchip Technology Inc. DS39632E-page 223 PIC18F2455/2550/4455/4550 FIGURE 19-15: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 7-BIT ADDRESS) SDA SCL SSPIF BF (SSPSTAT<0>) SSPOV (SSPCON1<6>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P A7 A6 A5 A4 A3 A2 A1 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D1 D0 R/W = 0 Receiving Data ACK Receiving Data ACK ACK Receiving Address Cleared in software SSPBUF is read Bus master terminates transfer SSPOV is set because SSPBUF is still full. ACK is not sent. D2 6 (PIR1<3>) CKP CKP written to ‘1’ in If BF is cleared prior to the falling edge of the ninth clock, CKP will not be reset to ‘0’ and no clock stretching will occur software Clock is held low until CKP is set to ‘1’ Clock is not held low because Buffer Full (BF) bit is clear prior to falling edge of ninth clock Clock is not held low because ACK = 1 BF is set after falling edge of the ninth clock, CKP is reset to ‘0’ and clock stretching occurs PIC18F2455/2550/4455/4550 DS39632E-page 224 © 2009 Microchip Technology Inc. FIGURE 19-16: I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 10-BIT ADDRESS) SDA SCL SSPIF (PIR1<3>) BF (SSPSTAT<0>) S 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 7 8 9 P 1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D1 D0 Receive Data Byte ACK R/W = 0 ACK Receive First Byte of Address Cleared in software D2 6 Cleared in software Receive Second Byte of Address Cleared by hardware when SSPADD is updated with low byte of address after falling edge UA (SSPSTAT<1>) Clock is held low until update of SSPADD has taken place UA is set indicating that the SSPADD needs to be updated UA is set indicating that SSPADD needs to be updated Cleared by hardware when SSPADD is updated with high byte of address after falling edge SSPBUF is written with contents of SSPSR Dummy read of SSPBUF to clear BF flag ACK CKP 1 2 3 4 5 7 8 9 D7 D6 D5 D4 D3 D1 D0 Receive Data Byte Bus master terminates transfer D2 6 ACK Cleared in software Cleared in software SSPOV (SSPCON1<6>) CKP written to ‘1’ Note: An update of the SSPADD register before the falling edge of the ninth clock will have no effect on UA and UA will remain set. Note: An update of the SSPADD register before the falling edge of the ninth clock will have no effect on UA and UA will remain set. in software Clock is held low until update of SSPADD has taken place of ninth clock of ninth clock SSPOV is set because SSPBUF is still full. ACK is not sent. Dummy read of SSPBUF to clear BF flag Clock is held low until CKP is set to ‘1’ Clock is not held low because ACK = 1 © 2009 Microchip Technology Inc. DS39632E-page 225 PIC18F2455/2550/4455/4550 19.4.5 GENERAL CALL ADDRESS SUPPORT The addressing procedure for the I2C bus is such that the first byte after the Start condition usually determines which device will be the slave addressed by the master. The exception is the general call address which can address all devices. When this address is used, all devices should, in theory, respond with an Acknowledge. The general call address is one of eight addresses reserved for specific purposes by the I2C protocol. It consists of all ‘0’s with R/W = 0. The general call address is recognized when the General Call Enable (GCEN) bit is enabled (SSPCON2<7> set). Following a Start bit detect, 8 bits are shifted into the SSPSR and the address is compared against the SSPADD. It is also compared to the general call address and fixed in hardware. If the general call address matches, the SSPSR is transferred to the SSPBUF, the BF flag bit is set (eighth bit) and on the falling edge of the ninth bit (ACK bit), the SSPIF interrupt flag bit is set. When the interrupt is serviced, the source for the interrupt can be checked by reading the contents of the SSPBUF. The value can be used to determine if the address was device specific or a general call address. In 10-bit mode, the SSPADD is required to be updated for the second half of the address to match and the UA bit is set (SSPSTAT<1>). If the general call address is sampled when the GCEN bit is set, while the slave is configured in 10-Bit Addressing mode, then the second half of the address is not necessary, the UA bit will not be set and the slave will begin receiving data after the Acknowledge (Figure 19-17). FIGURE 19-17: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE (7 OR 10-BIT ADDRESSING MODE) SDA SCL S SSPIF BF (SSPSTAT<0>) SSPOV (SSPCON1<6>) Cleared in software SSPBUF is read R/W = 0 General Call Address ACK Address is compared to General Call Address GCEN (SSPCON2<7>) Receiving Data ACK 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 D7 D6 D5 D4 D3 D2 D1 D0 after ACK, set interrupt ‘0’ ‘1’ PIC18F2455/2550/4455/4550 DS39632E-page 226 © 2009 Microchip Technology Inc. 19.4.6 MASTER MODE Master mode is enabled by setting and clearing the appropriate SSPM bits in SSPCON1 and by setting the SSPEN bit. In Master mode, the SCL and SDA lines are manipulated by the MSSP hardware if the TRIS bits are set. Master mode operation is supported by interrupt generation on the detection of the Start and Stop conditions. The Stop (P) and Start (S) bits are cleared from a Reset or when the MSSP module is disabled. Control of the I2C bus may be taken when the P bit is set or the bus is Idle, with both the S and P bits clear. In Firmware Controlled Master mode, user code conducts all I2C bus operations based on Start and Stop bit conditions. Once Master mode is enabled, the user has six options: 1. Assert a Start condition on SDA and SCL. 2. Assert a Repeated Start condition on SDA and SCL. 3. Write to the SSPBUF register initiating transmission of data/address. 4. Configure the I2C port to receive data. 5. Generate an Acknowledge condition at the end of a received byte of data. 6. Generate a Stop condition on SDA and SCL. The following events will cause the MSSP Interrupt Flag bit, SSPIF, to be set (and MSSP interrupt, if enabled): • Start condition • Stop condition • Data transfer byte transmitted/received • Acknowledge transmit • Repeated Start FIGURE 19-18: MSSP BLOCK DIAGRAM (I2C™ MASTER MODE) Note: The MSSP module, when configured in I2C Master mode, does not allow queueing of events. For instance, the user is not allowed to initiate a Start condition and immediately write the SSPBUF register to initiate transmission before the Start condition is complete. In this case, the SSPBUF will not be written to and the WCOL bit will be set, indicating that a write to the SSPBUF did not occur. Read Write SSPSR Start bit, Stop bit, SSPBUF Internal Data Bus Set/Reset S, P, WCOL (SSPSTAT, SSPCON1); Shift Clock MSb LSb SDA Acknowledge Generate Stop bit Detect Write Collision Detect Clock Arbitration State Counter for End of XMIT/RCV SCL SCL In Bus Collision SDA In Receive Enable Clock Cntl Clock Arbitrate/WCOL Detect (hold off clock source) SSPADD<6:0> Baud set SSPIF, BCLIF; reset ACKSTAT, PEN (SSPCON2) Rate Generator SSPM3:SSPM0 Start bit Detect © 2009 Microchip Technology Inc. DS39632E-page 227 PIC18F2455/2550/4455/4550 19.4.6.1 I2C Master Mode Operation The master device generates all of the serial clock pulses and the Start and Stop conditions. A transfer is ended with a Stop condition or with a Repeated Start condition. Since the Repeated Start condition is also the beginning of the next serial transfer, the I2C bus will not be released. In Master Transmitter mode, serial data is output through SDA, while SCL outputs the serial clock. The first byte transmitted contains the slave address of the receiving device (seven bits) and the Read/Write (R/W) bit. In this case, the R/W bit will be logic ‘0’. Serial data is transmitted eight bits at a time. After each byte is transmitted, an Acknowledge bit is received. Start and Stop conditions are output to indicate the beginning and the end of a serial transfer. In Master Receive mode, the first byte transmitted contains the slave address of the transmitting device (7 bits) and the R/W bit. In this case, the R/W bit will be logic ‘1’ Thus, the first byte transmitted is a 7-bit slave address followed by a ‘1’ to indicate the receive bit. Serial data is received via SDA, while SCL outputs the serial clock. Serial data is received eight bits at a time. After each byte is received, an Acknowledge bit is transmitted. Start and Stop conditions indicate the beginning and end of transmission. The Baud Rate Generator used for the SPI mode operation is used to set the SCL clock frequency for either 100 kHz, 400 kHz or 1 MHz I2C operation. See Section 19.4.7 “Baud Rate” for more detail. A typical transmit sequence would go as follows: 1. The user generates a Start condition by setting the Start Enable bit, SEN (SSPCON2<0>). 2. SSPIF is set. The MSSP module will wait the required start time before any other operation takes place. 3. The user loads the SSPBUF with the slave address to transmit. 4. Address is shifted out the SDA pin until all eight bits are transmitted. 5. The MSSP module shifts in the ACK bit from the slave device and writes its value into the SSPCON2 register (SSPCON2<6>). 6. The MSSP module generates an interrupt at the end of the ninth clock cycle by setting the SSPIF bit. 7. The user loads the SSPBUF with eight bits of data. 8. Data is shifted out the SDA pin until all eight bits are transmitted. 9. The MSSP module shifts in the ACK bit from the slave device and writes its value into the SSPCON2 register (SSPCON2<6>). 10. The MSSP module generates an interrupt at the end of the ninth clock cycle by setting the SSPIF bit. 11. The user generates a Stop condition by setting the Stop Enable bit, PEN (SSPCON2<2>). 12. Interrupt is generated once the Stop condition is complete. PIC18F2455/2550/4455/4550 DS39632E-page 228 © 2009 Microchip Technology Inc. 19.4.7 BAUD RATE In I2C Master mode, the Baud Rate Generator (BRG) reload value is placed in the lower seven bits of the SSPADD register (Figure 19-19). When a write occurs to SSPBUF, the Baud Rate Generator will automatically begin counting. The BRG counts down to ‘0’ and stops until another reload has taken place. The BRG count is decremented twice per instruction cycle (TCY) on the Q2 and Q4 clocks. In I2C Master mode, the BRG is reloaded automatically. Once the given operation is complete (i.e., transmission of the last data bit is followed by ACK), the internal clock will automatically stop counting and the SCL pin will remain in its last state. Table 19-3 demonstrates clock rates based on instruction cycles and the BRG value loaded into SSPADD. SSPADD values of less than 2 are not supported. Due to the need to support I2C clock stretching capability, I2C baud rates are partially dependent upon system parameters, such as line capacitance and pull-up strength. The parameters provided in Table 19-3 are guidelines, and the actual baud rate may be slightly slower than that predicted in the table. The baud rate formula shown in the bit description of Register 19-4 sets the maximum baud rate that can occur for a given SSPADD value. FIGURE 19-19: BAUD RATE GENERATOR BLOCK DIAGRAM TABLE 19-3: I2C™ CLOCK RATE W/BRG SSPM3:SSPM0 CLKO BRG Down Counter FOSC/4 SSPADD<6:0> SSPM3:SSPM0 SCL Reload Control Reload FCY FCY * 2 BRG Value FSCL (2 Rollovers of BRG) 10 MHz 20 MHz 18h 400 kHz(1) 10 MHz 20 MHz 1Fh 312.5 kHz 10 MHz 20 MHz 63h 100 kHz 4 MHz 8 MHz 09h 400 kHz(1) 4 MHz 8 MHz 0Ch 308 kHz 4 MHz 8 MHz 27h 100 kHz 1 MHz 2 MHz 02h 333 kHz(1) 1 MHz 2 MHz 09h 100 kHz Note 1: The I2C™ interface does not conform to the 400 kHz I2C specification (which applies to rates greater than 100 kHz) in all details, but may be used with care where higher rates are required by the application. © 2009 Microchip Technology Inc. DS39632E-page 229 PIC18F2455/2550/4455/4550 19.4.7.1 Clock Arbitration Clock arbitration occurs when the master, during any receive, transmit or Repeated Start/Stop condition, deasserts the SCL pin (SCL allowed to float high). When the SCL pin is allowed to float high, the Baud Rate Generator (BRG) is suspended from counting until the SCL pin is actually sampled high. When the SCL pin is sampled high, the Baud Rate Generator is reloaded with the contents of SSPADD<6:0> and begins counting. This ensures that the SCL high time will always be at least one BRG rollover count in the event that the clock is held low by an external device (Figure 19-20). FIGURE 19-20: BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION SDA SCL SCL deasserted but slave holds DX DX – 1 BRG SCL is sampled high, reload takes place and BRG starts its count 03h 02h 01h 00h (hold off) 03h 02h Reload BRG Value SCL low (clock arbitration) SCL allowed to transition high BRG decrements on Q2 and Q4 cycles PIC18F2455/2550/4455/4550 DS39632E-page 230 © 2009 Microchip Technology Inc. 19.4.8 I2C MASTER MODE START CONDITION TIMING To initiate a Start condition, the user sets the Start Enable bit, SEN (SSPCON2<0>). If the SDA and SCL pins are sampled high, the Baud Rate Generator is reloaded with the contents of SSPADD<6:0> and starts its count. If SCL and SDA are both sampled high when the Baud Rate Generator times out (TBRG), the SDA pin is driven low. The action of the SDA being driven low while SCL is high is the Start condition and causes the S bit (SSPSTAT<3>) to be set. Following this, the Baud Rate Generator is reloaded with the contents of SSPADD<6:0> and resumes its count. When the Baud Rate Generator times out (TBRG), the SEN bit (SSPCON2<0>) will be automatically cleared by hardware, the Baud Rate Generator is suspended, leaving the SDA line held low and the Start condition is complete. 19.4.8.1 WCOL Status Flag If the user writes the SSPBUF when a Start sequence is in progress, the WCOL bit is set and the contents of the buffer are unchanged (the write doesn’t occur). FIGURE 19-21: FIRST START BIT TIMING Note: If, at the beginning of the Start condition, the SDA and SCL pins are already sampled low, or if during the Start condition, the SCL line is sampled low before the SDA line is driven low, a bus collision occurs, the Bus Collision Interrupt Flag, BCLIF, is set, the Start condition is aborted and the I2C module is reset into its Idle state. Note: Because queueing of events is not allowed, writing to the lower five bits of SSPCON2 is disabled until the Start condition is complete. SDA SCL S TBRG 1st bit 2nd bit TBRG SDA = 1, SCL = 1 At completion of Start bit, TBRG Write to SSPBUF occurs here hardware clears SEN bit TBRG Write to SEN bit occurs here Set S bit (SSPSTAT<3>) and sets SSPIF bit © 2009 Microchip Technology Inc. DS39632E-page 231 PIC18F2455/2550/4455/4550 19.4.9 I2C MASTER MODE REPEATED START CONDITION TIMING A Repeated Start condition occurs when the RSEN bit (SSPCON2<1>) is programmed high and the I2C logic module is in the Idle state. When the RSEN bit is set, the SCL pin is asserted low. When the SCL pin is sampled low, the Baud Rate Generator is loaded with the contents of SSPADD<5:0> and begins counting. The SDA pin is released (brought high) for one Baud Rate Generator count (TBRG). When the Baud Rate Generator times out, if SDA is sampled high, the SCL pin will be deasserted (brought high). When SCL is sampled high, the Baud Rate Generator is reloaded with the contents of SSPADD<6:0> and begins counting. SDA and SCL must be sampled high for one TBRG. This action is then followed by assertion of the SDA pin (SDA = 0) for one TBRG while SCL is high. Following this, the RSEN bit (SSPCON2<1>) will be automatically cleared and the Baud Rate Generator will not be reloaded, leaving the SDA pin held low. As soon as a Start condition is detected on the SDA and SCL pins, the S bit (SSPSTAT<3>) will be set. The SSPIF bit will not be set until the Baud Rate Generator has timed out. Immediately following the SSPIF bit getting set, the user may write the SSPBUF with the 7-bit address in 7-bit mode or the default first address in 10-bit mode. After the first eight bits are transmitted and an ACK is received, the user may then transmit an additional eight bits of address (10-bit mode) or eight bits of data (7-bit mode). 19.4.9.1 WCOL Status Flag If the user writes the SSPBUF when a Repeated Start sequence is in progress, the WCOL bit is set and the contents of the buffer are unchanged (the write doesn’t occur). FIGURE 19-22: REPEATED START CONDITION WAVEFORM Note 1: If RSEN is programmed while any other event is in progress, it will not take effect. 2: A bus collision during the Repeated Start condition occurs if: • SDA is sampled low when SCL goes from low-to-high. • SCL goes low before SDA is asserted low. This may indicate that another master is attempting to transmit a data ‘1’. Note: Because queueing of events is not allowed, writing of the lower five bits of SSPCON2 is disabled until the Repeated Start condition is complete. SDA SCL Sr = Repeated Start Write to SSPCON2 Falling edge of ninth clock, Write to SSPBUF occurs here end of Xmit At completion of Start bit, hardware clears RSEN bit 1st bit Set S (SSPSTAT<3>) TBRG TBRG SDA = 1, SDA = 1, SCL (no change). SCL = 1 occurs here. TBRG TBRG TBRG and sets SSPIF PIC18F2455/2550/4455/4550 DS39632E-page 232 © 2009 Microchip Technology Inc. 19.4.10 I2C MASTER MODE TRANSMISSION Transmission of a data byte, a 7-bit address, or the other half of a 10-bit address is accomplished by simply writing a value to the SSPBUF register. This action will set the Buffer Full flag bit, BF, and allow the Baud Rate Generator to begin counting and start the next transmission. Each bit of address/data will be shifted out onto the SDA pin after the falling edge of SCL is asserted (see data hold time specification parameter 106). SCL is held low for one Baud Rate Generator rollover count (TBRG). Data should be valid before SCL is released high (see data setup time specification parameter 107). When the SCL pin is released high, it is held that way for TBRG. The data on the SDA pin must remain stable for that duration and some hold time after the next falling edge of SCL. After the eighth bit is shifted out (the falling edge of the eighth clock), the BF flag is cleared and the master releases SDA. This allows the slave device being addressed to respond with an ACK bit during the ninth bit time if an address match occurred, or if data was received properly. The status of ACK is written into the ACKDT bit on the falling edge of the ninth clock. If the master receives an Acknowledge, the Acknowledge Status bit, ACKSTAT, is cleared. If not, the bit is set. After the ninth clock, the SSPIF bit is set and the master clock (Baud Rate Generator) is suspended until the next data byte is loaded into the SSPBUF, leaving SCL low and SDA unchanged (Figure 19-23). After the write to the SSPBUF, each bit of the address will be shifted out on the falling edge of SCL until all seven address bits and the R/W bit are completed. On the falling edge of the eighth clock, the master will deassert the SDA pin, allowing the slave to respond with an Acknowledge. On the falling edge of the ninth clock, the master will sample the SDA pin to see if the address was recognized by a slave. The status of the ACK bit is loaded into the ACKSTAT status bit (SSPCON2<6>). Following the falling edge of the ninth clock transmission of the address, the SSPIF is set, the BF flag is cleared and the Baud Rate Generator is turned off until another write to the SSPBUF takes place, holding SCL low and allowing SDA to float. 19.4.10.1 BF Status Flag In Transmit mode, the BF bit (SSPSTAT<0>) is set when the CPU writes to SSPBUF and is cleared when all eight bits are shifted out. 19.4.10.2 WCOL Status Flag If the user writes the SSPBUF when a transmit is already in progress (i.e., SSPSR is still shifting out a data byte), the WCOL bit is set and the contents of the buffer are unchanged (the write doesn’t occur) after 2 TCY after the SSPBUF write. If SSPBUF is rewritten within 2 TCY, the WCOL bit is set and SSPBUF is updated. This may result in a corrupted transfer. The user should verify that the WCOL is clear after each write to SSPBUF to ensure the transfer is correct. In all cases, WCOL must be cleared in software. 19.4.10.3 ACKSTAT Status Flag In Transmit mode, the ACKSTAT bit (SSPCON2<6>) is cleared when the slave has sent an Acknowledge (ACK = 0) and is set when the slave does not Acknowledge (ACK = 1). A slave sends an Acknowledge when it has recognized its address (including a general call), or when the slave has properly received its data. 19.4.11 I2C MASTER MODE RECEPTION Master mode reception is enabled by programming the Receive Enable bit, RCEN (SSPCON2<3>). The Baud Rate Generator begins counting and on each rollover, the state of the SCL pin changes (high-to-low/ low-to-high) and data is shifted into the SSPSR. After the falling edge of the eighth clock, the receive enable flag is automatically cleared, the contents of the SSPSR are loaded into the SSPBUF, the BF flag bit is set, the SSPIF flag bit is set and the Baud Rate Generator is suspended from counting, holding SCL low. The MSSP is now in Idle state awaiting the next command. When the buffer is read by the CPU, the BF flag bit is automatically cleared. The user can then send an Acknowledge bit at the end of reception by setting the Acknowledge Sequence Enable bit, ACKEN (SSPCON2<4>). 19.4.11.1 BF Status Flag In receive operation, the BF bit is set when an address or data byte is loaded into SSPBUF from SSPSR. It is cleared when the SSPBUF register is read. 19.4.11.2 SSPOV Status Flag In receive operation, the SSPOV bit is set when eight bits are received into the SSPSR and the BF flag bit is already set from a previous reception. 19.4.11.3 WCOL Status Flag If the user writes the SSPBUF when a receive is already in progress (i.e., SSPSR is still shifting in a data byte), the WCOL bit is set and the contents of the buffer are unchanged (the write doesn’t occur). Note: The MSSP module must be in an Idle state before the RCEN bit is set or the RCEN bit will be disregarded. © 2009 Microchip Technology Inc. DS39632E-page 233 PIC18F2455/2550/4455/4550 FIGURE 19-23: I2C™ MASTER MODE WAVEFORM (TRANSMISSION, 7 OR 10-BIT ADDRESS) SDA SCL SSPIF BF (SSPSTAT<0>) SEN A7 A6 A5 A4 A3 A2 A1 ACK = 0 D7 D6 D5 D4 D3 D2 D1 D0 ACK Transmitting Data or Second Half Transmit Address to Slave R/W = 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 P Cleared in software service routine SSPBUF is written in software from MSSP interrupt After Start condition, SEN cleared by hardware S SSPBUF written with 7-bit address and R/W start transmit SCL held low while CPU responds to SSPIF SEN = 0 of 10-Bit Address Write SSPCON2<0> SEN = 1, Start condition begins From slave, clear ACKSTAT bit SSPCON2<6> ACKSTAT in SSPCON2 = 1 Cleared in software SSPBUF written PEN R/W Cleared in software PIC18F2455/2550/4455/4550 DS39632E-page 234 © 2009 Microchip Technology Inc. FIGURE 19-24: I2C™ MASTER MODE WAVEFORM (RECEPTION, 7-BIT ADDRESS) 5 6 7 8 9 P D7 D6 D5 D4 D3 D2 D1 D0 S SDA A7 A6 A5 A4 A3 A2 A1 SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 Bus master terminates transfer ACK Receiving Data from Slave Receiving Data from Slave ACK D7 D6 D5 D4 D3 D2 D1 D0 Transmit Address to Slave R/W = 1 SSPIF BF ACK is not sent Write to SSPCON2<0> (SEN = 1), Write to SSPBUF occurs here, ACK from Slave Master configured as a receiver by programming SSPCON2<3> (RCEN = 1) PEN bit = 1 written here Data shifted in on falling edge of CLK Cleared in software start XMIT SEN = 0 SSPOV SDA = 0, SCL = 1 while CPU (SSPSTAT<0>) ACK Cleared in software Cleared in software Set SSPIF interrupt at end of receive Set P bit (SSPSTAT<4>) and SSPIF ACK from master, Set SSPIF at end Set SSPIF interrupt at end of Acknowledge sequence Set SSPIF interrupt at end of Acknowledge sequence of receive Set ACKEN, start Acknowledge sequence, SDA = ACKDT = 1 RCEN cleared automatically RCEN = 1, start next receive Write to SSPCON2<4> to start Acknowledge sequence SDA = ACKDT (SSPCON2<5>) = 0 RCEN cleared automatically responds to SSPIF ACKEN begin Start Condition Cleared in software SDA = ACKDT = 0 Cleared in software SSPOV is set because SSPBUF is still full Last bit is shifted into SSPSR and contents are unloaded into SSPBUF © 2009 Microchip Technology Inc. DS39632E-page 235 PIC18F2455/2550/4455/4550 19.4.12 ACKNOWLEDGE SEQUENCE TIMING An Acknowledge sequence is enabled by setting the Acknowledge Sequence Enable bit, ACKEN (SSPCON2<4>). When this bit is set, the SCL pin is pulled low and the contents of the Acknowledge data bit are presented on the SDA pin. If the user wishes to generate an Acknowledge, then the ACKDT bit should be cleared. If not, the user should set the ACKDT bit before starting an Acknowledge sequence. The Baud Rate Generator then counts for one rollover period (TBRG) and the SCL pin is deasserted (pulled high). When the SCL pin is sampled high (clock arbitration), the Baud Rate Generator counts for TBRG. The SCL pin is then pulled low. Following this, the ACKEN bit is automatically cleared, the Baud Rate Generator is turned off and the MSSP module then goes into an inactive state (Figure 19-25). 19.4.12.1 WCOL Status Flag If the user writes the SSPBUF when an Acknowledge sequence is in progress, then WCOL is set and the contents of the buffer are unchanged (the write doesn’t occur). 19.4.13 STOP CONDITION TIMING A Stop bit is asserted on the SDA pin at the end of a receive/transmit by setting the Stop Enable bit, PEN (SSPCON2<2>). At the end of a receive/transmit, the SCL line is held low after the falling edge of the ninth clock. When the PEN bit is set, the master will assert the SDA line low. When the SDA line is sampled low, the Baud Rate Generator is reloaded and counts down to 0. When the Baud Rate Generator times out, the SCL pin will be brought high and one TBRG (Baud Rate Generator rollover count) later, the SDA pin will be deasserted. When the SDA pin is sampled high while SCL is high, the P bit (SSPSTAT<4>) is set. A TBRG later, the PEN bit is cleared and the SSPIF bit is set (Figure 19-26). 19.4.13.1 WCOL Status Flag If the user writes the SSPBUF when a Stop sequence is in progress, then the WCOL bit is set and the contents of the buffer are unchanged (the write doesn’t occur). FIGURE 19-25: ACKNOWLEDGE SEQUENCE WAVEFORM FIGURE 19-26: STOP CONDITION RECEIVE OR TRANSMIT MODE Note: TBRG = one Baud Rate Generator period. SDA SCL Set SSPIF at the Acknowledge sequence starts here, write to SSPCON2 ACKEN automatically cleared Cleared in TBRG TBRG end of receive 8 ACKEN = 1, ACKDT = 0 D0 9 SSPIF software Set SSPIF at the end of Acknowledge sequence Cleared in software ACK SCL SDA SDA asserted low before rising edge of clock Write to SSPCON2, set PEN Falling edge of SCL = 1 for TBRG, followed by SDA = 1 for TBRG ninth clock SCL brought high after TBRG Note: TBRG = one Baud Rate Generator period. TBRG TBRG after SDA sampled high. P bit (SSPSTAT<4>) is set. TBRG to setup Stop condition ACK P TBRG PEN bit (SSPCON2<2>) is cleared by hardware and the SSPIF bit is set PIC18F2455/2550/4455/4550 DS39632E-page 236 © 2009 Microchip Technology Inc. 19.4.14 SLEEP OPERATION While in Sleep mode, the I2C module can receive addresses or data and when an address match or complete byte transfer occurs, wake the processor from Sleep (if the MSSP interrupt is enabled). 19.4.15 EFFECTS OF A RESET A Reset disables the MSSP module and terminates the current transfer. 19.4.16 MULTI-MASTER MODE In Multi-Master mode, the interrupt generation on the detection of the Start and Stop conditions allows the determination of when the bus is free. The Stop (P) and Start (S) bits are cleared from a Reset or when the MSSP module is disabled. Control of the I2C bus may be taken when the P bit (SSPSTAT<4>) is set, or the bus is Idle, with both the S and P bits clear. When the bus is busy, enabling the MSSP interrupt will generate the interrupt when the Stop condition occurs. In multi-master operation, the SDA line must be monitored for arbitration to see if the signal level is the expected output level. This check is performed in hardware with the result placed in the BCLIF bit. The states where arbitration can be lost are: • Address Transfer • Data Transfer • A Start Condition • A Repeated Start Condition • An Acknowledge Condition 19.4.17 MULTI -MASTER COMMUNICATION, BUS COLLISION AND BUS ARBITRATION Multi-Master mode support is achieved by bus arbitration. When the master outputs address/data bits onto the SDA pin, arbitration takes place when the master outputs a ‘1’ on SDA, by letting SDA float high and another master asserts a ‘0’. When the SCL pin floats high, data should be stable. If the expected data on SDA is a ‘1’ and the data sampled on the SDA pin = 0, then a bus collision has taken place. The master will set the Bus Collision Interrupt Flag, BCLIF, and reset the I2C port to its Idle state (Figure 19-27). If a transmit was in progress when the bus collision occurred, the transmission is halted, the BF flag is cleared, the SDA and SCL lines are deasserted and the SSPBUF can be written to. When the user services the bus collision Interrupt Service Routine, and if the I2C bus is free, the user can resume communication by asserting a Start condition. If a Start, Repeated Start, Stop or Acknowledge condition was in progress when the bus collision occurred, the condition is aborted, the SDA and SCL lines are deasserted and the respective control bits in the SSPCON2 register are cleared. When the user services the bus collision Interrupt Service Routine, and if the I2C bus is free, the user can resume communication by asserting a Start condition. The master will continue to monitor the SDA and SCL pins. If a Stop condition occurs, the SSPIF bit will be set. A write to the SSPBUF bit will start the transmission of data at the first data bit regardless of where the transmitter left off when the bus collision occurred. In Multi-Master mode, the interrupt generation on the detection of Start and Stop conditions allows the determination of when the bus is free. Control of the I2C bus can be taken when the P bit is set in the SSPSTAT register, or the bus is Idle and the S and P bits are cleared. FIGURE 19-27: BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE SDA SCL BCLIF SDA released SDA line pulled low by another source Sample SDA. While SCL is high, data doesn’t match what is driven Bus collision has occurred. Set Bus Collision Interrupt Flag (BCLIF) by the master. by master Data changes while SCL = 0 © 2009 Microchip Technology Inc. DS39632E-page 237 PIC18F2455/2550/4455/4550 19.4.17.1 Bus Collision During a Start Condition During a Start condition, a bus collision occurs if: a) SDA or SCL are sampled low at the beginning of the Start condition (Figure 19-28). b) SCL is sampled low before SDA is asserted low (Figure 19-29). During a Start condition, both the SDA and the SCL pins are monitored. If the SDA pin is already low, or the SCL pin is already low, then all of the following occur: • the Start condition is aborted, • the BCLIF flag is set and • the MSSP module is reset to its inactive state (Figure 19-28). The Start condition begins with the SDA and SCL pins deasserted. When the SDA pin is sampled high, the Baud Rate Generator is loaded from SSPADD<6:0> and counts down to ‘0’. If the SCL pin is sampled low while SDA is high, a bus collision occurs because it is assumed that another master is attempting to drive a data ‘1’ during the Start condition. If the SDA pin is sampled low during this count, the BRG is reset and the SDA line is asserted early (Figure 19-30). If, however, a ‘1’ is sampled on the SDA pin, the SDA pin is asserted low at the end of the BRG count. The Baud Rate Generator is then reloaded and counts down to 0. If the SCL pin is sampled as ‘0’, during this time a bus collision does not occur. At the end of the BRG count, the SCL pin is asserted low. FIGURE 19-28: BUS COLLISION DURING START CONDITION (SDA ONLY) Note: The reason that bus collision is not a factor during a Start condition is that no two bus masters can assert a Start condition at the exact same time. Therefore, one master will always assert SDA before the other. This condition does not cause a bus collision because the two masters must be allowed to arbitrate the first address following the Start condition. If the address is the same, arbitration must be allowed to continue into the data portion, Repeated Start or Stop conditions. SDA SCL SEN SDA sampled low before SDA goes low before the SEN bit is set. S bit and SSPIF set because MSSP module reset into Idle state. SEN cleared automatically because of bus collision. S bit and SSPIF set because Set SEN, enable Start condition if SDA = 1, SCL = 1 SDA = 0, SCL = 1. BCLIF S SSPIF SDA = 0, SCL = 1. SSPIF and BCLIF are cleared in software SSPIF and BCLIF are cleared in software Set BCLIF, Start condition. Set BCLIF. PIC18F2455/2550/4455/4550 DS39632E-page 238 © 2009 Microchip Technology Inc. FIGURE 19-29: BUS COLLISION DURING START CONDITION (SCL = 0) FIGURE 19-30: BRG RESET DUE TO SDA ARBITRATION DURING START CONDITION SDA SCL SEN bus collision occurs. Set BCLIF. SCL = 0 before SDA = 0, Set SEN, enable Start sequence if SDA = 1, SCL = 1 TBRG TBRG SDA = 0, SCL = 1 BCLIF S SSPIF Interrupt cleared in software bus collision occurs. Set BCLIF. SCL = 0 before BRG time-out, ‘0’ ‘0’ ‘0’ ‘0’ SDA SCL SEN Set S Less than TBRG TBRG SDA = 0, SCL = 1 BCLIF S SSPIF S Interrupts cleared set SSPIF in software SDA = 0, SCL = 1, SCL pulled low after BRG time-out Set SSPIF ‘0’ SDA pulled low by other master. Reset BRG and assert SDA. Set SEN, enable Start sequence if SDA = 1, SCL = 1 © 2009 Microchip Technology Inc. DS39632E-page 239 PIC18F2455/2550/4455/4550 19.4.17.2 Bus Collision During a Repeated Start Condition During a Repeated Start condition, a bus collision occurs if: a) A low level is sampled on SDA when SCL goes from low level to high level. b) SCL goes low before SDA is asserted low, indicating that another master is attempting to transmit a data ‘1’. When the user deasserts SDA and the pin is allowed to float high, the BRG is loaded with SSPADD<6:0> and counts down to ‘0’. The SCL pin is then deasserted and when sampled high, the SDA pin is sampled. If SDA is low, a bus collision has occurred (i.e., another master is attempting to transmit a data ‘0’, see Figure 19-31). If SDA is sampled high, the BRG is reloaded and begins counting. If SDA goes from high-tolow before the BRG times out, no bus collision occurs because no two masters can assert SDA at exactly the same time. If SCL goes from high-to-low before the BRG times out and SDA has not already been asserted, a bus collision occurs. In this case, another master is attempting to transmit a data ‘1’ during the Repeated Start condition (see Figure 19-32). If, at the end of the BRG time-out, both SCL and SDA are still high, the SDA pin is driven low and the BRG is reloaded and begins counting. At the end of the count, regardless of the status of the SCL pin, the SCL pin is driven low and the Repeated Start condition is complete. FIGURE 19-31: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1) FIGURE 19-32: BUS COLLISION DURING REPEATED START CONDITION (CASE 2) SDA SCL RSEN BCLIF S SSPIF Sample SDA when SCL goes high. If SDA = 0, set BCLIF and release SDA and SCL. Cleared in software ‘0’ ‘0’ SDA SCL BCLIF RSEN S SSPIF Interrupt cleared in software SCL goes low before SDA, set BCLIF. Release SDA and SCL. TBRG TBRG ‘0’ PIC18F2455/2550/4455/4550 DS39632E-page 240 © 2009 Microchip Technology Inc. 19.4.17.3 Bus Collision During a Stop Condition Bus collision occurs during a Stop condition if: a) After the SDA pin has been deasserted and allowed to float high, SDA is sampled low after the BRG has timed out. b) After the SCL pin is deasserted, SCL is sampled low before SDA goes high. The Stop condition begins with SDA asserted low. When SDA is sampled low, the SCL pin is allowed to float. When the pin is sampled high (clock arbitration), the Baud Rate Generator is loaded with SSPADD<6:0> and counts down to 0. After the BRG times out, SDA is sampled. If SDA is sampled low, a bus collision has occurred. This is due to another master attempting to drive a data ‘0’. (Figure 19-33). If the SCL pin is sampled low before SDA is allowed to float high, a bus collision occurs. This is another case of another master attempting to drive a data ‘0’ (Figure 19-34). FIGURE 19-33: BUS COLLISION DURING A STOP CONDITION (CASE 1) FIGURE 19-34: BUS COLLISION DURING A STOP CONDITION (CASE 2) SDA SCL BCLIF PEN P SSPIF TBRG TBRG TBRG SDA asserted low SDA sampled low after TBRG, set BCLIF ‘0’ ‘0’ SDA SCL BCLIF PEN P SSPIF TBRG TBRG TBRG Assert SDA SCL goes low before SDA goes high, set BCLIF ‘0’ ‘0’ © 2009 Microchip Technology Inc. DS39632E-page 241 PIC18F2455/2550/4455/4550 TABLE 19-4: REGISTERS ASSOCIATED WITH I2C™ OPERATION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on Page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 TRISC TRISC7 TRISC6 — — — TRISC2 TRISC1 TRISC0 56 TRISD(1) TRISD7 TRISD6 TRISD5 TRISD4 TRISD3 TRISD2 TRISD1 TRISD0 56 SSPBUF MSSP Receive Buffer/Transmit Register 54 SSPADD MSSP Address Register in I2C Slave mode. MSSP Baud Rate Reload Register in I2C Master mode. 54 TMR2 Timer2 Register 54 PR2 Timer2 Period Register 54 SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 54 SSPCON2 GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN 54 SSPSTAT SMP CKE D/A P S R/W UA BF 54 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the MSSP in I2C™ mode. Note 1: These registers or bits are not implemented in 28-pin devices. PIC18F2455/2550/4455/4550 DS39632E-page 242 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 243 PIC18F2455/2550/4455/4550 20.0 ENHANCED UNIVERSAL SYNCHRONOUS ASYNCHRONOUS RECEIVER TRANSMITTER (EUSART) The Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) module is one of the two serial I/O modules. (Generically, the USART is also known as a Serial Communications Interface or SCI.) The EUSART can be configured as a full-duplex asynchronous system that can communicate with peripheral devices, such as CRT terminals and personal computers. It can also be configured as a halfduplex synchronous system that can communicate with peripheral devices, such as A/D or D/A integrated circuits, serial EEPROMs, etc. The Enhanced USART module implements additional features, including automatic baud rate detection and calibration, automatic wake-up on Sync Break reception and 12-bit Break character transmit. These make it ideally suited for use in Local Interconnect Network bus (LIN bus) systems. The EUSART can be configured in the following modes: • Asynchronous (full-duplex) with: - Auto-wake-up on Break signal - Auto-baud calibration - 12-bit Break character transmission • Synchronous – Master (half-duplex) with selectable clock polarity • Synchronous – Slave (half-duplex) with selectable clock polarity The pins of the Enhanced USART are multiplexed with PORTC. In order to configure RC6/TX/CK and RC7/RX/DT/SDO as an EUSART: • SPEN bit (RCSTA<7>) must be set (= 1) • TRISC<7> bit must be set (= 1) • TRISC<6> bit must be set (= 1) The operation of the Enhanced USART module is controlled through three registers: • Transmit Status and Control (TXSTA) • Receive Status and Control (RCSTA) • Baud Rate Control (BAUDCON) These are detailed on the following pages in Register 20-1, Register 20-2 and Register 20-3, respectively. Note: The EUSART control will automatically reconfigure the pin from input to output as needed. PIC18F2455/2550/4455/4550 DS39632E-page 244 © 2009 Microchip Technology Inc. REGISTER 20-1: TXSTA: TRANSMIT STATUS AND CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-1 R/W-0 CSRC TX9 TXEN(1) SYNC SENDB BRGH TRMT TX9D bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 CSRC: Clock Source Select bit Asynchronous mode: Don’t care. Synchronous mode: 1 = Master mode (clock generated internally from BRG) 0 = Slave mode (clock from external source) bit 6 TX9: 9-Bit Transmit Enable bit 1 = Selects 9-bit transmission 0 = Selects 8-bit transmission bit 5 TXEN: Transmit Enable bit(1) 1 = Transmit enabled 0 = Transmit disabled bit 4 SYNC: EUSART Mode Select bit 1 = Synchronous mode 0 = Asynchronous mode bit 3 SENDB: Send Break Character bit Asynchronous mode: 1 = Send Sync Break on next transmission (cleared by hardware upon completion) 0 = Sync Break transmission completed Synchronous mode: Don’t care. bit 2 BRGH: High Baud Rate Select bit Asynchronous mode: 1 = High speed 0 = Low speed Synchronous mode: Unused in this mode. bit 1 TRMT: Transmit Shift Register Status bit 1 = TSR empty 0 = TSR full bit 0 TX9D: 9th bit of Transmit Data Can be address/data bit or a parity bit. Note 1: SREN/CREN overrides TXEN in Sync mode with the exception that SREN has no effect in Synchronous Slave mode. © 2009 Microchip Technology Inc. DS39632E-page 245 PIC18F2455/2550/4455/4550 REGISTER 20-2: RCSTA: RECEIVE STATUS AND CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R-0 R-x SPEN RX9 SREN CREN ADDEN FERR OERR RX9D bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 SPEN: Serial Port Enable bit 1 = Serial port enabled (configures RX/DT and TX/CK pins as serial port pins) 0 = Serial port disabled (held in Reset) bit 6 RX9: 9-Bit Receive Enable bit 1 = Selects 9-bit reception 0 = Selects 8-bit reception bit 5 SREN: Single Receive Enable bit Asynchronous mode: Don’t care. Synchronous mode – Master: 1 = Enables single receive 0 = Disables single receive This bit is cleared after reception is complete. Synchronous mode – Slave: Don’t care. bit 4 CREN: Continuous Receive Enable bit Asynchronous mode: 1 = Enables receiver 0 = Disables receiver Synchronous mode: 1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN) 0 = Disables continuous receive bit 3 ADDEN: Address Detect Enable bit Asynchronous mode 9-bit (RX9 = 1): 1 = Enables address detection, enables interrupt and loads the receive buffer when RSR<8> is set 0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit Asynchronous mode 8-bit (RX9 = 0): Don’t care. bit 2 FERR: Framing Error bit 1 = Framing error (can be updated by reading RCREG register and receiving next valid byte) 0 = No framing error bit 1 OERR: Overrun Error bit 1 = Overrun error (can be cleared by clearing bit CREN) 0 = No overrun error bit 0 RX9D: 9th bit of Received Data This can be address/data bit or a parity bit and must be calculated by user firmware. PIC18F2455/2550/4455/4550 DS39632E-page 246 © 2009 Microchip Technology Inc. REGISTER 20-3: BAUDCON: BAUD RATE CONTROL REGISTER R/W-0 R-1 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 ABDOVF: Auto-Baud Acquisition Rollover Status bit 1 = A BRG rollover has occurred during Auto-Baud Rate Detect mode (must be cleared in software) 0 = No BRG rollover has occurred bit 6 RCIDL: Receive Operation Idle Status bit 1 = Receive operation is Idle 0 = Receive operation is active bit 5 RXDTP: Received Data Polarity Select bit Asynchronous mode: 1 = RX data is inverted 0 = RX data received is not inverted Synchronous modes: 1 = Received Data (DT) is inverted. Idle state is a low level. 0 = No inversion of Data (DT). Idle state is a high level. bit 4 TXCKP: Clock and Data Polarity Select bit Asynchronous mode: 1 = TX data is inverted 0 = TX data is not inverted Synchronous modes: 1 = Clock (CK) is inverted. Idle state is a high level. 0 = No inversion of Clock (CK). Idle state is a low level. bit 3 BRG16: 16-Bit Baud Rate Register Enable bit 1 = 16-bit Baud Rate Generator – SPBRGH and SPBRG 0 = 8-bit Baud Rate Generator – SPBRG only (Compatible mode), SPBRGH value ignored bit 2 Unimplemented: Read as ‘0’ bit 1 WUE: Wake-up Enable bit Asynchronous mode: 1 = EUSART will continue to sample the RX pin – interrupt generated on falling edge; bit cleared in hardware on following rising edge 0 = RX pin not monitored or rising edge detected Synchronous mode: Unused in this mode. bit 0 ABDEN: Auto-Baud Detect Enable bit Asynchronous mode: 1 = Enable baud rate measurement on the next character. Requires reception of a Sync field (55h); cleared in hardware upon completion. 0 = Baud rate measurement disabled or completed Synchronous mode: Unused in this mode. © 2009 Microchip Technology Inc. DS39632E-page 247 PIC18F2455/2550/4455/4550 20.1 Baud Rate Generator (BRG) The BRG is a dedicated 8-bit, or 16-bit, generator that supports both the Asynchronous and Synchronous modes of the EUSART. By default, the BRG operates in 8-bit mode. Setting the BRG16 bit (BAUDCON<3>) selects 16-bit mode. The SPBRGH:SPBRG register pair controls the period of a free-running timer. In Asynchronous mode, bits, BRGH (TXSTA<2>) and BRG16 (BAUDCON<3>), also control the baud rate. In Synchronous mode, BRGH is ignored. Table 20-1 shows the formula for computation of the baud rate for different EUSART modes which only apply in Master mode (internally generated clock). Given the desired baud rate and FOSC, the nearest integer value for the SPBRGH:SPBRG registers can be calculated using the formulas in Table 20-1. From this, the error in baud rate can be determined. An example calculation is shown in Example 20-1. Typical baud rates and error values for the various Asynchronous modes are shown in Table 20-2. It may be advantageous to use the high baud rate (BRGH = 1), or the 16-bit BRG to reduce the baud rate error, or achieve a slow baud rate for a fast oscillator frequency. Writing a new value to the SPBRGH:SPBRG registers causes the BRG timer to be reset (or cleared). This ensures the BRG does not wait for a timer overflow before outputting the new baud rate. 20.1.1 OPERATION IN POWER-MANAGED MODES The device clock is used to generate the desired baud rate. When one of the power-managed modes is entered, the new clock source may be operating at a different frequency. This may require an adjustment to the value in the SPBRG register pair. 20.1.2 SAMPLING The data on the RX pin is sampled three times by a majority detect circuit to determine if a high or a low level is present at the RX pin. TABLE 20-1: BAUD RATE FORMULAS Configuration Bits BRG/EUSART Mode Baud Rate Formula SYNC BRG16 BRGH 0 0 0 8-bit/Asynchronous FOSC/[64 (n + 1)] 0 0 1 8-bit/Asynchronous FOSC/[16 (n + 1)] 0 1 0 16-bit/Asynchronous 0 1 1 16-bit/Asynchronous 1 0 x 8-bit/Synchronous FOSC/[4 (n + 1)] 1 1 x 16-bit/Synchronous Legend: x = Don’t care, n = value of SPBRGH:SPBRG register pair PIC18F2455/2550/4455/4550 DS39632E-page 248 © 2009 Microchip Technology Inc. EXAMPLE 20-1: CALCULATING BAUD RATE ERROR TABLE 20-2: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR For a device with FOSC of 16 MHz, desired baud rate of 9600, Asynchronous mode, 8-bit BRG: Desired Baud Rate = FOSC/(64 ([SPBRGH:SPBRG] + 1)) Solving for SPBRGH:SPBRG: X = ((FOSC/Desired Baud Rate)/64) – 1 = ((16000000/9600)/64) – 1 = [25.042] = 25 Calculated Baud Rate = 16000000/(64 (25 + 1)) = 9615 Error = (Calculated Baud Rate – Desired Baud Rate)/Desired Baud Rate = (9615 – 9600)/9600 = 0.16% Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the BRG. © 2009 Microchip Technology Inc. DS39632E-page 249 PIC18F2455/2550/4455/4550 TABLE 20-3: BAUD RATES FOR ASYNCHRONOUS MODES BAUD RATE (K) SYNC = 0, BRGH = 0, BRG16 = 0 FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 — — — — — — — — — — — — 1.2 — — — 1.221 1.73 255 1.202 0.16 129 1.201 -0.16 103 2.4 2.441 1.73 255 2.404 0.16 129 2.404 0.16 64 2.403 -0.16 51 9.6 9.615 0.16 64 9.766 1.73 31 9.766 1.73 15 9.615 -0.16 12 19.2 19.531 1.73 31 19.531 1.73 15 19.531 1.73 7 — — — 57.6 56.818 -1.36 10 62.500 8.51 4 52.083 -9.58 2 — — — 115.2 125.000 8.51 4 104.167 -9.58 2 78.125 -32.18 1 — — — BAUD RATE (K) SYNC = 0, BRGH = 0, BRG16 = 0 FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 0.300 0.16 207 0.300 -0.16 103 0.300 -0.16 51 1.2 1.202 0.16 51 1.201 -0.16 25 1.201 -0.16 12 2.4 2.404 0.16 25 2.403 -0.16 12 — — — 9.6 8.929 -6.99 6 — — — — — — 19.2 20.833 8.51 2 — — — — — — 57.6 62.500 8.51 0 — — — — — — 115.2 62.500 -45.75 0 — — — — — — BAUD RATE (K) SYNC = 0, BRGH = 1, BRG16 = 0 FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 — — — — — — — — — — — — 1.2 — — — — — — — — — — — — 2.4 — — — — — — 2.441 1.73 255 2.403 -0.16 207 9.6 9.766 1.73 255 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51 19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25 57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8 115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4 — — — BAUD RATE (K) SYNC = 0, BRGH = 1, BRG16 = 0 FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 — — — — — — 0.300 -0.16 207 1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51 2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25 9.6 9.615 0.16 25 9.615 -0.16 12 — — — 19.2 19.231 0.16 12 — — — — — — 57.6 62.500 8.51 3 — — — — — — 115.2 125.000 8.51 1 — — — — — — PIC18F2455/2550/4455/4550 DS39632E-page 250 © 2009 Microchip Technology Inc. BAUD RATE (K) SYNC = 0, BRGH = 0, BRG16 = 1 FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 0.300 0.00 8332 0.300 0.02 4165 0.300 0.02 2082 0.300 -0.04 1665 1.2 1.200 0.02 2082 1.200 -0.03 1041 1.200 -0.03 520 1.201 -0.16 415 2.4 2.402 0.06 1040 2.399 -0.03 520 2.404 0.16 259 2.403 -0.16 207 9.6 9.615 0.16 259 9.615 0.16 129 9.615 0.16 64 9.615 -0.16 51 19.2 19.231 0.16 129 19.231 0.16 64 19.531 1.73 31 19.230 -0.16 25 57.6 58.140 0.94 42 56.818 -1.36 21 56.818 -1.36 10 55.555 3.55 8 115.2 113.636 -1.36 21 113.636 -1.36 10 125.000 8.51 4 — — — BAUD RATE (K) SYNC = 0, BRGH = 0, BRG16 = 1 FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 0.300 0.04 832 0.300 -0.16 415 0.300 -0.16 207 1.2 1.202 0.16 207 1.201 -0.16 103 1.201 -0.16 51 2.4 2.404 0.16 103 2.403 -0.16 51 2.403 -0.16 25 9.6 9.615 0.16 25 9.615 -0.16 12 — — — 19.2 19.231 0.16 12 — — — — — — 57.6 62.500 8.51 3 — — — — — — 115.2 125.000 8.51 1 — — — — — — BAUD RATE (K) SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1 FOSC = 40.000 MHz FOSC = 20.000 MHz FOSC = 10.000 MHz FOSC = 8.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 0.300 0.00 33332 0.300 0.00 16665 0.300 0.00 8332 0.300 -0.01 6665 1.2 1.200 0.00 8332 1.200 0.02 4165 1.200 0.02 2082 1.200 -0.04 1665 2.4 2.400 0.02 4165 2.400 0.02 2082 2.402 0.06 1040 2.400 -0.04 832 9.6 9.606 0.06 1040 9.596 -0.03 520 9.615 0.16 259 9.615 -0.16 207 19.2 19.193 -0.03 520 19.231 0.16 259 19.231 0.16 129 19.230 -0.16 103 57.6 57.803 0.35 172 57.471 -0.22 86 58.140 0.94 42 57.142 0.79 34 115.2 114.943 -0.22 86 116.279 0.94 42 113.636 -1.36 21 117.647 -2.12 16 BAUD RATE (K) SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1 FOSC = 4.000 MHz FOSC = 2.000 MHz FOSC = 1.000 MHz Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) Actual Rate (K) % Error SPBRG value (decimal) 0.3 0.300 0.01 3332 0.300 -0.04 1665 0.300 -0.04 832 1.2 1.200 0.04 832 1.201 -0.16 415 1.201 -0.16 207 2.4 2.404 0.16 415 2.403 -0.16 207 2.403 -0.16 103 9.6 9.615 0.16 103 9.615 -0.16 51 9.615 -0.16 25 19.2 19.231 0.16 51 19.230 -0.16 25 19.230 -0.16 12 57.6 58.824 2.12 16 55.555 3.55 8 — — — 115.2 111.111 -3.55 8 — — — — — — TABLE 20-3: BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED) © 2009 Microchip Technology Inc. DS39632E-page 251 PIC18F2455/2550/4455/4550 20.1.3 AUTO-BAUD RATE DETECT The Enhanced USART module supports the automatic detection and calibration of baud rate. This feature is active only in Asynchronous mode and while the WUE bit is clear. The automatic baud rate measurement sequence (Figure 20-1) begins whenever a Start bit is received and the ABDEN bit is set. The calculation is self-averaging. In the Auto-Baud Rate Detect (ABD) mode, the clock to the BRG is reversed. Rather than the BRG clocking the incoming RX signal, the RX signal is timing the BRG. In ABD mode, the internal Baud Rate Generator is used as a counter to time the bit period of the incoming serial byte stream. Once the ABDEN bit is set, the state machine will clear the BRG and look for a Start bit. The Auto-Baud Rate Detect must receive a byte with the value, 55h (ASCII “U”, which is also the LIN bus Sync character), in order to calculate the proper bit rate. The measurement is taken over both a low and a high bit time in order to minimize any effects caused by asymmetry of the incoming signal. After a Start bit, the SPBRG begins counting up, using the preselected clock source on the first rising edge of RX. After eight bits on the RX pin, or the fifth rising edge, an accumulated value totalling the proper BRG period is left in the SPBRGH:SPBRG register pair. Once the 5th edge is seen (this should correspond to the Stop bit), the ABDEN bit is automatically cleared. If a rollover of the BRG occurs (an overflow from FFFFh to 0000h), the event is trapped by the ABDOVF status bit (BAUDCON<7>). It is set in hardware by BRG rollovers and can be set or cleared by the user in software. ABD mode remains active after rollover events and the ABDEN bit remains set (Figure 20-2). While calibrating the baud rate period, the BRG registers are clocked at 1/8th the preconfigured clock rate. Note that the BRG clock will be configured by the BRG16 and BRGH bits. Independent of the BRG16 bit setting, both the SPBRG and SPBRGH will be used as a 16-bit counter. This allows the user to verify that no carry occurred for 8-bit modes by checking for 00h in the SPBRGH register. Refer to Table 20-4 for counter clock rates to the BRG. While the ABD sequence takes place, the EUSART state machine is held in Idle. The RCIF interrupt is set once the fifth rising edge on RX is detected. The value in the RCREG needs to be read to clear the RCIF interrupt. The contents of RCREG should be discarded. TABLE 20-4: BRG COUNTER CLOCK RATES 20.1.3.1 ABD and EUSART Transmission Since the BRG clock is reversed during ABD acquisition, the EUSART transmitter cannot be used during ABD. This means that whenever the ABDEN bit is set, TXREG cannot be written to. Users should also ensure that ABDEN does not become set during a transmit sequence. Failing to do this may result in unpredictable EUSART operation. Note 1: If the WUE bit is set with the ABDEN bit, Auto-Baud Rate Detection will occur on the byte following the Break character. 2: It is up to the user to determine that the incoming character baud rate is within the range of the selected BRG clock source. Some combinations of oscillator frequency and EUSART baud rates are not possible due to bit error rates. Overall system timing and communication baud rates must be taken into consideration when using the Auto-Baud Rate Detection feature. BRG16 BRGH BRG Counter Clock 0 0 FOSC/512 0 1 FOSC/128 1 0 FOSC/128 1 1 FOSC/32 Note: During the ABD sequence, SPBRG and SPBRGH are both used as a 16-bit counter, independent of the BRG16 setting. PIC18F2455/2550/4455/4550 DS39632E-page 252 © 2009 Microchip Technology Inc. FIGURE 20-1: AUTOMATIC BAUD RATE CALCULATION FIGURE 20-2: BRG OVERFLOW SEQUENCE BRG Value RX pin ABDEN bit RCIF bit bit 0 bit 1 (Interrupt) Read RCREG BRG Clock Start Set by User Auto-Cleared XXXXh 0000h Edge #1 bit 2 bit 3 Edge #2 bit 4 bit 5 Edge #3 bit 6 bit 7 Edge #4 001Ch Note: The ABD sequence requires the EUSART module to be configured in Asynchronous mode and WUE = 0. SPBRG XXXXh 1Ch SPBRGH XXXXh 00h Stop bit Edge #5 Start bit 0 XXXXh 0000h 0000h FFFFh BRG Clock ABDEN bit RX pin ABDOVF bit BRG Value © 2009 Microchip Technology Inc. DS39632E-page 253 PIC18F2455/2550/4455/4550 20.2 EUSART Asynchronous Mode The Asynchronous mode of operation is selected by clearing the SYNC bit (TXSTA<4>). In this mode, the EUSART uses standard Non-Return-to-Zero (NRZ) format (one Start bit, eight or nine data bits and one Stop bit). The most common data format is 8 bits. An on-chip dedicated 8-bit/16-bit Baud Rate Generator can be used to derive standard baud rate frequencies from the oscillator. The EUSART transmits and receives the LSb first. The EUSART’s transmitter and receiver are functionally independent but use the same data format and baud rate. The Baud Rate Generator produces a clock, either x16 or x64 of the bit shift rate depending on the BRGH and BRG16 bits (TXSTA<2> and BAUDCON<3>). Parity is not supported by the hardware but can be implemented in software and stored as the 9th data bit. The TXCKP (BAUDCON<4>) and RXDTP (BAUDCON<5>) bits allow the TX and RX signals to be inverted (polarity reversed). Devices that buffer signals between TTL and RS-232 levels also invert the signal. Setting the TXCKP and RXDTP bits allows for the use of circuits that provide buffering without inverting the signal. When operating in Asynchronous mode, the EUSART module consists of the following important elements: • Baud Rate Generator • Sampling Circuit • Asynchronous Transmitter • Asynchronous Receiver • Auto-Wake-up on Break signal • 12-Bit Break Character Transmit • Auto-Baud Rate Detection • Pin State Polarity 20.2.1 EUSART ASYNCHRONOUS TRANSMITTER The EUSART transmitter block diagram is shown in Figure 20-3. The heart of the transmitter is the Transmit (Serial) Shift Register (TSR). The Shift register obtains its data from the Read/Write Transmit Buffer register, TXREG. The TXREG register is loaded with data in software. The TSR register is not loaded until the Stop bit has been transmitted from the previous load. As soon as the Stop bit is transmitted, the TSR is loaded with new data from the TXREG register (if available). Once the TXREG register transfers the data to the TSR register (occurs in one TCY), the TXREG register is empty and the TXIF flag bit (PIR1<4>) is set. This interrupt can be enabled or disabled by setting or clearing the interrupt enable bit, TXIE (PIE1<4>). TXIF will be set regardless of the state of TXIE; it cannot be cleared in software. TXIF is also not cleared immediately upon loading TXREG, but becomes valid in the second instruction cycle following the load instruction. Polling TXIF immediately following a load of TXREG will return invalid results. While TXIF indicates the status of the TXREG register, another bit, TRMT (TXSTA<1>), shows the status of the TSR register. TRMT is a read-only bit which is set when the TSR register is empty. No interrupt logic is tied to this bit so the user has to poll this bit in order to determine if the TSR register is empty. The TXCKP bit (BAUDCON<4>) allows the TX signal to be inverted (polarity reversed). Devices that buffer signals from TTL to RS-232 levels also invert the signal (when TTL = 1, RS-232 = negative). Inverting the polarity of the TX pin data by setting the TXCKP bit allows for use of circuits that provide buffering without inverting the signal. To set up an Asynchronous Transmission: 1. Initialize the SPBRGH:SPBRG registers for the appropriate baud rate. Set or clear the BRGH and BRG16 bits, as required, to achieve the desired baud rate. 2. Enable the asynchronous serial port by clearing bit, SYNC, and setting bit, SPEN. 3. If the signal from the TX pin is to be inverted, set the TXCKP bit. 4. If interrupts are desired, set enable bit, TXIE. 5. If 9-bit transmission is desired, set transmit bit, TX9. Can be used as address/data bit. 6. Enable the transmission by setting bit, TXEN, which will also set bit, TXIF. 7. If 9-bit transmission is selected, the ninth bit should be loaded in bit, TX9D. 8. Load data to the TXREG register (starts transmission). 9. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. Note 1: The TSR register is not mapped in data memory so it is not available to the user. 2: Flag bit, TXIF, is set when enable bit, TXEN, is set. PIC18F2455/2550/4455/4550 DS39632E-page 254 © 2009 Microchip Technology Inc. FIGURE 20-3: EUSART TRANSMIT BLOCK DIAGRAM FIGURE 20-4: ASYNCHRONOUS TRANSMISSION, TXCKP = 0 (TX NOT INVERTED) FIGURE 20-5: ASYNCHRONOUS TRANSMISSION (BACK TO BACK), TXCKP = 0 (TX NOT INVERTED) TXIF TXIE Interrupt TXEN Baud Rate CLK SPBRG Baud Rate Generator TX9D MSb LSb Data Bus TXREG Register TSR Register (8) 0 TX9 TRMT SPEN TX pin Pin Buffer and Control 8 • • • BRG16 SPBRGH TXCKP Word 1 Word 1 Transmit Shift Reg Start bit bit 0 bit 1 bit 7/8 Write to TXREG BRG Output (Shift Clock) TX (pin) TXIF bit (Transmit Buffer Reg. Empty Flag) TRMT bit (Transmit Shift Reg. Empty Flag) 1 TCY Stop bit Word 1 Transmit Shift Reg. Write to TXREG BRG Output (Shift Clock) TX (pin) TXIF bit (Interrupt Reg. Flag) TRMT bit (Transmit Shift Reg. Empty Flag) Word 1 Word 2 Word 1 Word 2 Stop bit Start bit Transmit Shift Reg. Word 1 Word 2 bit 0 bit 1 bit 7/8 bit 0 Note: This timing diagram shows two consecutive transmissions. 1 TCY 1 TCY Start bit © 2009 Microchip Technology Inc. DS39632E-page 255 PIC18F2455/2550/4455/4550 TABLE 20-5: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 TXREG EUSART Transmit Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous transmission. Note 1: Reserved in 28-pin devices; always maintain these bits clear. PIC18F2455/2550/4455/4550 DS39632E-page 256 © 2009 Microchip Technology Inc. 20.2.2 EUSART ASYNCHRONOUS RECEIVER The receiver block diagram is shown in Figure 20-6. The data is received on the RX pin and drives the data recovery block. The data recovery block is actually a high-speed shifter operating at x16 times the baud rate, whereas the main receive serial shifter operates at the bit rate or at FOSC. This mode would typically be used in RS-232 systems. The RXDTP bit (BAUDCON<5>) allows the RX signal to be inverted (polarity reversed). Devices that buffer signals from RS-232 to TTL levels also perform an inversion of the signal (when RS-232 = positive, TTL = 0). Inverting the polarity of the RX pin data by setting the RXDTP bit allows for the use of circuits that provide buffering without inverting the signal. To set up an Asynchronous Reception: 1. Initialize the SPBRGH:SPBRG registers for the appropriate baud rate. Set or clear the BRGH and BRG16 bits, as required, to achieve the desired baud rate. 2. Enable the asynchronous serial port by clearing bit, SYNC, and setting bit, SPEN. 3. If the signal at the RX pin is to be inverted, set the RXDTP bit. 4. If interrupts are desired, set enable bit, RCIE. 5. If 9-bit reception is desired, set bit, RX9. 6. Enable the reception by setting bit, CREN. 7. Flag bit, RCIF, will be set when reception is complete and an interrupt will be generated if enable bit, RCIE, was set. 8. Read the RCSTA register to get the 9th bit (if enabled) and determine if any error occurred during reception. 9. Read the 8-bit received data by reading the RCREG register. 10. If any error occurred, clear the error by clearing enable bit, CREN. 11. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. 20.2.3 SETTING UP 9-BIT MODE WITH ADDRESS DETECT This mode would typically be used in RS-485 systems. To set up an Asynchronous Reception with Address Detect Enable: 1. Initialize the SPBRGH:SPBRG registers for the appropriate baud rate. Set or clear the BRGH and BRG16 bits, as required, to achieve the desired baud rate. 2. Enable the asynchronous serial port by clearing the SYNC bit and setting the SPEN bit. 3. If the signal at the RX pin is to be inverted, set the RXDTP bit. If the signal from the TX pin is to be inverted, set the TXCKP bit. 4. If interrupts are required, set the RCEN bit and select the desired priority level with the RCIP bit. 5. Set the RX9 bit to enable 9-bit reception. 6. Set the ADDEN bit to enable address detect. 7. Enable reception by setting the CREN bit. 8. The RCIF bit will be set when reception is complete. The interrupt will be Acknowledged if the RCIE and GIE bits are set. 9. Read the RCSTA register to determine if any error occurred during reception, as well as read bit 9 of data (if applicable). 10. Read RCREG to determine if the device is being addressed. 11. If any error occurred, clear the CREN bit. 12. If the device has been addressed, clear the ADDEN bit to allow all received data into the receive buffer and interrupt the CPU. © 2009 Microchip Technology Inc. DS39632E-page 257 PIC18F2455/2550/4455/4550 FIGURE 20-6: EUSART RECEIVE BLOCK DIAGRAM FIGURE 20-7: ASYNCHRONOUS RECEPTION, RXDTP = 0 (RX NOT INVERTED) TABLE 20-6: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 RCREG EUSART Receive Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception. Note 1: Reserved in 28-pin devices; always maintain these bits clear. x64 Baud Rate CLK Baud Rate Generator RX Pin Buffer and Control SPEN Data Recovery CREN OERR FERR MSb RSR Register LSb RX9D RCREG Register FIFO Interrupt RCIF RCIE Data Bus 8 ÷ 64 ÷ 16 or Stop (8) 7 1 0 Start RX9 • • • BRG16 SPBRGH SPBRG or ÷ 4 RXDTP Start bit bit 0 bit 1 bit 7/8 Stop bit 0 bit 7/8 bit Start bit Start bit 7/8 Stop bit bit RX (pin) Rcv Buffer Reg Rcv Shift Reg Read Rcv Buffer Reg RCREG RCIF (Interrupt Flag) OERR bit CREN Word 1 RCREG Word 2 RCREG Stop bit Note: This timing diagram shows three words appearing on the RX input. The RCREG (Receive Buffer) is read after the third word causing the OERR (Overrun) bit to be set. PIC18F2455/2550/4455/4550 DS39632E-page 258 © 2009 Microchip Technology Inc. 20.2.4 AUTO-WAKE-UP ON SYNC BREAK CHARACTER During Sleep mode, all clocks to the EUSART are suspended. Because of this, the Baud Rate Generator is inactive and a proper byte reception cannot be performed. The auto-wake-up feature allows the controller to wake-up due to activity on the RX/DT line while the EUSART is operating in Asynchronous mode. The auto-wake-up feature is enabled by setting the WUE bit (BAUDCON<1>). Once set, the typical receive sequence on RX/DT is disabled and the EUSART remains in an Idle state, monitoring for a wake-up event independent of the CPU mode. A wake-up event consists of a high-to-low transition on the RX/DT line. (This coincides with the start of a Sync Break or a Wake-up Signal character for the LIN protocol.) Following a wake-up event, the module generates an RCIF interrupt. The interrupt is generated synchronously to the Q clocks in normal operating modes (Figure 20-8) and asynchronously, if the device is in Sleep mode (Figure 20-9). The interrupt condition is cleared by reading the RCREG register. The WUE bit is automatically cleared once a low-tohigh transition is observed on the RX line following the wake-up event. At this point, the EUSART module is in Idle mode and returns to normal operation. This signals to the user that the Sync Break event is over. 20.2.4.1 Special Considerations Using Auto-Wake-up Since auto-wake-up functions by sensing rising edge transitions on RX/DT, information with any state changes before the Stop bit may signal a false End-Of- Character and cause data or framing errors. To work properly, therefore, the initial character in the transmission must be all ‘0’s. This can be 00h (8 bits) for standard RS-232 devices or 000h (12 bits) for LIN bus. Oscillator start-up time must also be considered, especially in applications using oscillators with longer start-up intervals (i.e., XT or HS mode). The Sync Break (or Wake-up Signal) character must be of sufficient length and be followed by a sufficient interval to allow enough time for the selected oscillator to start and provide proper initialization of the EUSART. 20.2.4.2 Special Considerations Using the WUE Bit The timing of WUE and RCIF events may cause some confusion when it comes to determining the validity of received data. As noted, setting the WUE bit places the EUSART in an Idle mode. The wake-up event causes a receive interrupt by setting the RCIF bit. The WUE bit is cleared after this when a rising edge is seen on RX/DT. The interrupt condition is then cleared by reading the RCREG register. Ordinarily, the data in RCREG will be dummy data and should be discarded. The fact that the WUE bit has been cleared (or is still set) and the RCIF flag is set should not be used as an indicator of the integrity of the data in RCREG. Users should consider implementing a parallel method in firmware to verify received data integrity. To assure that no actual data is lost, check the RCIDL bit to verify that a receive operation is not in process. If a receive operation is not occurring, the WUE bit may then be set just prior to entering the Sleep mode. FIGURE 20-8: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING NORMAL OPERATION FIGURE 20-9: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 OSC1 WUE bit(1) RX/DT Line RCIF Note 1: The EUSART remains in Idle while the WUE bit is set. Bit set by user Cleared due to user read of RCREG Auto-Cleared Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 OSC1 WUE bit(2) RX/DT Line RCIF Bit set by user Cleared due to user read of RCREG Sleep Command Executed Note 1: If the wake-up event requires long oscillator warm-up time, the auto-clear of the WUE bit can occur before the oscillator is ready. This sequence should not depend on the presence of Q clocks. 2: The EUSART remains in Idle while the WUE bit is set. Sleep Ends Note 1 Auto-Cleared © 2009 Microchip Technology Inc. DS39632E-page 259 PIC18F2455/2550/4455/4550 20.2.5 BREAK CHARACTER SEQUENCE The EUSART module has the capability of sending the special Break character sequences that are required by the LIN bus standard. The Break character transmit consists of a Start bit, followed by twelve ‘0’ bits and a Stop bit. The Frame Break character is sent whenever the SENDB and TXEN bits (TXSTA<3> and TXSTA<5>) are set while the Transmit Shift Register is loaded with data. Note that the value of data written to TXREG will be ignored and all ‘0’s will be transmitted. The SENDB bit is automatically reset by hardware after the corresponding Stop bit is sent. This allows the user to preload the transmit FIFO with the next transmit byte following the Break character (typically, the Sync character in the LIN specification). Note that the data value written to the TXREG for the Break character is ignored. The write simply serves the purpose of initiating the proper sequence. The TRMT bit indicates when the transmit operation is active or Idle, just as it does during normal transmission. See Figure 20-10 for the timing of the Break character sequence. 20.2.5.1 Break and Sync Transmit Sequence The following sequence will send a message frame header made up of a Break, followed by an Auto-Baud Sync byte. This sequence is typical of a LIN bus master. 1. Configure the EUSART for the desired mode. 2. Set the TXEN and SENDB bits to set up the Break character. 3. Load the TXREG with a dummy character to initiate transmission (the value is ignored). 4. Write ‘55h’ to TXREG to load the Sync character into the transmit FIFO buffer. 5. After the Break has been sent, the SENDB bit is reset by hardware. The Sync character now transmits in the preconfigured mode. When the TXREG becomes empty, as indicated by the TXIF, the next data byte can be written to TXREG. 20.2.6 RECEIVING A BREAK CHARACTER The Enhanced USART module can receive a Break character in two ways. The first method forces configuration of the baud rate at a frequency of 9/13 the typical speed. This allows for the Stop bit transition to be at the correct sampling location (13 bits for Break versus Start bit and 8 data bits for typical data). The second method uses the auto-wake-up feature described in Section 20.2.4 “Auto-Wake-up on Sync Break Character”. By enabling this feature, the EUSART will sample the next two transitions on RX/DT, cause an RCIF interrupt and receive the next data byte followed by another interrupt. Note that following a Break character, the user will typically want to enable the Auto-Baud Rate Detect feature. For both methods, the user can set the ABD bit once the TXIF interrupt is observed. FIGURE 20-10: SEND BREAK CHARACTER SEQUENCE Write to TXREG BRG Output (Shift Clock) Start bit bit 0 bit 1 bit 11 Stop bit Break TXIF bit (Transmit Buffer Reg. Empty Flag) TX (pin) TRMT bit (Transmit Shift Reg. Empty Flag) SENDB (Transmit Shift Reg. Empty Flag) SENDB sampled here Auto-Cleared Dummy Write PIC18F2455/2550/4455/4550 DS39632E-page 260 © 2009 Microchip Technology Inc. 20.3 EUSART Synchronous Master Mode The Synchronous Master mode is entered by setting the CSRC bit (TXSTA<7>). In this mode, the data is transmitted in a half-duplex manner (i.e., transmission and reception do not occur at the same time). When transmitting data, the reception is inhibited and vice versa. Synchronous mode is entered by setting bit, SYNC (TXSTA<4>). In addition, enable bit, SPEN (RCSTA<7>), is set in order to configure the TX and RX pins to CK (clock) and DT (data) lines, respectively. The Master mode indicates that the processor transmits the master clock on the CK line. Clock polarity (CK) is selected with the TXCKP bit (BAUDCON<4>). Setting TXCKP sets the Idle state on CK as high, while clearing the bit sets the Idle state as low. Data polarity (DT) is selected with the RXDTP bit (BAUDCON<5>). Setting RXDTP sets the Idle state on DT as high, while clearing the bit sets the Idle state as low. DT is sampled when CK returns to its idle state. This option is provided to support Microwire devices with this module. 20.3.1 EUSART SYNCHRONOUS MASTER TRANSMISSION The EUSART transmitter block diagram is shown in Figure 20-3. The heart of the transmitter is the Transmit (Serial) Shift Register (TSR). The Shift register obtains its data from the Read/Write Transmit Buffer register, TXREG. The TXREG register is loaded with data in software. The TSR register is not loaded until the last bit has been transmitted from the previous load. As soon as the last bit is transmitted, the TSR is loaded with new data from the TXREG (if available). Once the TXREG register transfers the data to the TSR register (occurs in one TCY), the TXREG is empty and the TXIF flag bit (PIR1<4>) is set. The interrupt can be enabled or disabled by setting or clearing the interrupt enable bit, TXIE (PIE1<4>). TXIF is set regardless of the state of enable bit, TXIE; it cannot be cleared in software. It will reset only when new data is loaded into the TXREG register. While flag bit, TXIF, indicates the status of the TXREG register, another bit, TRMT (TXSTA<1>), shows the status of the TSR register. TRMT is a read-only bit which is set when the TSR is empty. No interrupt logic is tied to this bit so the user has to poll this bit in order to determine if the TSR register is empty. The TSR is not mapped in data memory so it is not available to the user. To set up a Synchronous Master Transmission: 1. Initialize the SPBRGH:SPBRG registers for the appropriate baud rate. Set or clear the BRG16 bit, as required, to achieve the desired baud rate. 2. Enable the synchronous master serial port by setting bits, SYNC, SPEN and CSRC. 3. If interrupts are desired, set enable bit, TXIE. 4. If 9-bit transmission is desired, set bit, TX9. 5. Enable the transmission by setting bit, TXEN. 6. If 9-bit transmission is selected, the ninth bit should be loaded in bit, TX9D. 7. Start transmission by loading data to the TXREG register. 8. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. FIGURE 20-11: SYNCHRONOUS TRANSMISSION bit 0 bit 1 bit 7 Word 1 Q1Q2 Q3Q4 Q1 Q2Q3 Q4Q1Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1Q2 Q3 Q4 Q3 Q4 Q1Q2 Q3Q4 Q1Q2 Q3Q4 Q1 Q2Q3 Q4 Q1 Q2Q3 Q4 Q1Q2 Q3 Q4Q1 Q2 Q3 Q4 bit 2 bit 0 bit 1 bit 7 RC6/TX/CK pin Write to TXREG Reg TXIF bit (Interrupt Flag) TXEN bit ‘1’ ‘1’ Word 2 TRMT bit Write Word 1 Write Word 2 Note: Sync Master mode, SPBRG = 0, continuous transmission of two 8-bit words. RC6/TX/CK pin (TXCKP = 0) (TXCKP = 1) RC7/RX/DT/ SDO pin © 2009 Microchip Technology Inc. DS39632E-page 261 PIC18F2455/2550/4455/4550 FIGURE 20-12: SYNCHRONOUS TRANSMISSION (THROUGH TXEN) TABLE 20-7: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION RC7/RX/DT/SDO pin RC6/TX/CK pin Write to TXREG reg TXIF bit TRMT bit bit 0 bit 1 bit 2 bit 6 bit 7 TXEN bit Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 TXREG EUSART Transmit Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission. Note 1: Reserved in 28-pin devices; always maintain these bits clear. PIC18F2455/2550/4455/4550 DS39632E-page 262 © 2009 Microchip Technology Inc. 20.3.2 EUSART SYNCHRONOUS MASTER RECEPTION Once Synchronous mode is selected, reception is enabled by setting either the Single Receive Enable bit, SREN (RCSTA<5>), or the Continuous Receive Enable bit, CREN (RCSTA<4>). Data is sampled on the RX pin on the falling edge of the clock. If enable bit, SREN, is set, only a single word is received. If enable bit, CREN, is set, the reception is continuous until CREN is cleared. If both bits are set, then CREN takes precedence. To set up a Synchronous Master Reception: 1. Initialize the SPBRGH:SPBRG registers for the appropriate baud rate. Set or clear the BRG16 bit, as required, to achieve the desired baud rate. 2. Enable the synchronous master serial port by setting bits, SYNC, SPEN and CSRC. 3. Ensure bits, CREN and SREN, are clear. 4. If the signal from the CK pin is to be inverted, set the TXCKP bit. If the signal from the DT pin is to be inverted, set the RXDTP bit. 5. If interrupts are desired, set enable bit, RCIE. 6. If 9-bit reception is desired, set bit, RX9. 7. If a single reception is required, set bit, SREN. For continuous reception, set bit, CREN. 8. Interrupt flag bit, RCIF, will be set when reception is complete and an interrupt will be generated if the enable bit, RCIE, was set. 9. Read the RCSTA register to get the 9th bit (if enabled) and determine if any error occurred during reception. 10. Read the 8-bit received data by reading the RCREG register. 11. If any error occurred, clear the error by clearing bit, CREN. 12. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. FIGURE 20-13: SYNCHRONOUS RECEPTION (MASTER MODE, SREN) TABLE 20-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 RCREG EUSART Receive Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception. Note 1: Reserved in 28-pin devices; always maintain these bits clear. CREN bit RC7/RX/DT/SDO RC6/TX/CK pin Write to bit SREN SREN bit RCIF bit (Interrupt) Read RXREG Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2Q3 Q4 Q1 Q2 Q3 Q4 ‘0’ bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 ‘0’ Q1 Q2 Q3 Q4 Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0. RC6/TX/CK pin pin (TXCKP = 0) (TXCKP = 1) © 2009 Microchip Technology Inc. DS39632E-page 263 PIC18F2455/2550/4455/4550 20.4 EUSART Synchronous Slave Mode Synchronous Slave mode is entered by clearing bit, CSRC (TXSTA<7>). This mode differs from the Synchronous Master mode in that the shift clock is supplied externally at the CK pin (instead of being supplied internally in Master mode). This allows the device to transfer or receive data while in any power-managed mode. 20.4.1 EUSART SYNCHRONOUS SLAVE TRANSMISSION The operation of the Synchronous Master and Slave modes is identical, except in the case of the Sleep mode. If two words are written to the TXREG and then the SLEEP instruction is executed, the following will occur: a) The first word will immediately transfer to the TSR register and transmit. b) The second word will remain in the TXREG register. c) Flag bit, TXIF, will not be set. d) When the first word has been shifted out of TSR, the TXREG register will transfer the second word to the TSR and flag bit, TXIF, will now be set. e) If enable bit, TXIE, is set, the interrupt will wake the chip from Sleep. If the global interrupt is enabled, the program will branch to the interrupt vector. To set up a Synchronous Slave Transmission: 1. Enable the synchronous slave serial port by setting bits, SYNC and SPEN, and clearing bit, CSRC. 2. Clear bits, CREN and SREN. 3. If interrupts are desired, set enable bit, TXIE. 4. If the signal from the CK pin is to be inverted, set the TXCKP bit. If the signal from the DT pin is to be inverted, set the RXDTP bit. 5. If 9-bit transmission is desired, set bit, TX9. 6. Enable the transmission by setting enable bit, TXEN. 7. If 9-bit transmission is selected, the ninth bit should be loaded in bit, TX9D. 8. Start transmission by loading data to the TXREG register. 9. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. TABLE 20-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 TXREG EUSART Transmit Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave transmission. Note 1: Reserved in 28-pin devices; always maintain these bits clear. PIC18F2455/2550/4455/4550 DS39632E-page 264 © 2009 Microchip Technology Inc. 20.4.2 EUSART SYNCHRONOUS SLAVE RECEPTION The operation of the Synchronous Master and Slave modes is identical, except in the case of Sleep, or any Idle mode and bit, SREN, which is a “don’t care” in Slave mode. If receive is enabled by setting the CREN bit prior to entering Sleep or any Idle mode, then a word may be received while in this low-power mode. Once the word is received, the RSR register will transfer the data to the RCREG register. If the RCIE enable bit is set, the interrupt generated will wake the chip from the lowpower mode. If the global interrupt is enabled, the program will branch to the interrupt vector. To set up a Synchronous Slave Reception: 1. Enable the synchronous master serial port by setting bits, SYNC and SPEN, and clearing bit, CSRC. 2. If interrupts are desired, set enable bit, RCIE. 3. If the signal from the CK pin is to be inverted, set the TXCKP bit. If the signal from the DT pin is to be inverted, set the RXDTP bit. 4. If 9-bit reception is desired, set bit, RX9. 5. To enable reception, set enable bit, CREN. 6. Flag bit, RCIF, will be set when reception is complete. An interrupt will be generated if enable bit, RCIE, was set. 7. Read the RCSTA register to get the 9th bit (if enabled) and determine if any error occurred during reception. 8. Read the 8-bit received data by reading the RCREG register. 9. If any error occurred, clear the error by clearing bit, CREN. 10. If using interrupts, ensure that the GIE and PEIE bits in the INTCON register (INTCON<7:6>) are set. TABLE 20-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 55 RCREG EUSART Receive Register 55 TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 55 BAUDCON ABDOVF RCIDL RXDTP TXCKP BRG16 — WUE ABDEN 55 SPBRGH EUSART Baud Rate Generator Register High Byte 55 SPBRG EUSART Baud Rate Generator Register Low Byte 55 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception. Note 1: Reserved in 28-pin devices; always maintain these bits clear. © 2009 Microchip Technology Inc. DS39632E-page 265 PIC18F2455/2550/4455/4550 21.0 10-BIT ANALOG-TO-DIGITAL CONVERTER (A/D) MODULE The Analog-to-Digital (A/D) converter module has 10 inputs for the 28-pin devices and 13 for the 40/44-pin devices. This module allows conversion of an analog input signal to a corresponding 10-bit digital number. The module has five registers: • A/D Result High Register (ADRESH) • A/D Result Low Register (ADRESL) • A/D Control Register 0 (ADCON0) • A/D Control Register 1 (ADCON1) • A/D Control Register 2 (ADCON2) The ADCON0 register, shown in Register 21-1, controls the operation of the A/D module. The ADCON1 register, shown in Register 21-2, configures the functions of the port pins. The ADCON2 register, shown in Register 21-3, configures the A/D clock source, programmed acquisition time and justification. REGISTER 21-1: ADCON0: A/D CONTROL REGISTER 0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 — — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-6 Unimplemented: Read as ‘0’ bit 5-2 CHS3:CHS0: Analog Channel Select bits 0000 = Channel 0 (AN0) 0001 = Channel 1 (AN1) 0010 = Channel 2 (AN2) 0011 = Channel 3 (AN3) 0100 = Channel 4 (AN4) 0101 = Channel 5 (AN5)(1,2) 0110 = Channel 6 (AN6)(1,2) 0111 = Channel 7 (AN7)(1,2) 1000 = Channel 8 (AN8) 1001 = Channel 9 (AN9) 1010 = Channel 10 (AN10) 1011 = Channel 11 (AN11) 1100 = Channel 12 (AN12) 1101 = Unimplemented(2) 1110 = Unimplemented(2) 1111 = Unimplemented(2) bit 1 GO/DONE: A/D Conversion Status bit When ADON = 1: 1 = A/D conversion in progress 0 = A/D Idle bit 0 ADON: A/D On bit 1 = A/D converter module is enabled 0 = A/D converter module is disabled Note 1: These channels are not implemented on 28-pin devices. 2: Performing a conversion on unimplemented channels will return a floating input measurement. PIC18F2455/2550/4455/4550 DS39632E-page 266 © 2009 Microchip Technology Inc. REGISTER 21-2: ADCON1: A/D CONTROL REGISTER 1 U-0 U-0 R/W-0 R/W-0 R/W-0(1) R/W(1) R/W(1) R/W(1) — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-6 Unimplemented: Read as ‘0’ bit 5 VCFG1: Voltage Reference Configuration bit (VREF- source) 1 = VREF- (AN2) 0 = VSS bit 4 VCFG0: Voltage Reference Configuration bit (VREF+ source) 1 = VREF+ (AN3) 0 = VDD bit 3-0 PCFG3:PCFG0: A/D Port Configuration Control bits: Note 1: The POR value of the PCFG bits depends on the value of the PBADEN Configuration bit. When PBADEN = 1, PCFG<3:0> = 0000; when PBADEN = 0, PCFG<3:0> = 0111. 2: AN5 through AN7 are available only on 40/44-pin devices. A = Analog input D = Digital I/O PCFG3: PCFG0 AN12 AN11 AN10 AN9 AN8 AN7(2) AN6(2) AN5(2) AN4 AN3 AN2 AN1 AN0 0000(1) A A A A A A A A A A A A A 0001 A A A A A A A A A A A A A 0010 A A A A A A A A A A A A A 0011 D A A A A A A A A A A A A 0100 D D A A A A A A A A A A A 0101 D D D A A A A A A A A A A 0110 D D D D A A A A A A A A A 0111(1) D D D D D A A A A A A A A 1000 D D D D D D A A A A A A A 1001 D D D D D D D A A A A A A 1010 D D D D D D D D A A A A A 1011 D D D D D D D D D A A A A 1100 D D D D D D D D D D A A A 1101 D D D D D D D D D D D A A 1110 D D D D D D D D D D D D A 1111 D D D D D D D D D D D D D © 2009 Microchip Technology Inc. DS39632E-page 267 PIC18F2455/2550/4455/4550 REGISTER 21-3: ADCON2: A/D CONTROL REGISTER 2 R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 ADFM: A/D Result Format Select bit 1 = Right justified 0 = Left justified bit 6 Unimplemented: Read as ‘0’ bit 5-3 ACQT2:ACQT0: A/D Acquisition Time Select bits 111 = 20 TAD 110 = 16 TAD 101 = 12 TAD 100 = 8 TAD 011 = 6 TAD 010 = 4 TAD 001 = 2 TAD 000 = 0 TAD(1) bit 2-0 ADCS2:ADCS0: A/D Conversion Clock Select bits 111 = FRC (clock derived from A/D RC oscillator)(1) 110 = FOSC/64 101 = FOSC/16 100 = FOSC/4 011 = FRC (clock derived from A/D RC oscillator)(1) 010 = FOSC/32 001 = FOSC/8 000 = FOSC/2 Note 1: If the A/D FRC clock source is selected, a delay of one TCY (instruction cycle) is added before the A/D clock starts. This allows the SLEEP instruction to be executed before starting a conversion. PIC18F2455/2550/4455/4550 DS39632E-page 268 © 2009 Microchip Technology Inc. The analog reference voltage is software selectable to either the device’s positive and negative supply voltage (VDD and VSS) or the voltage level on the RA3/AN3/VREF+ and RA2/AN2/VREF-/CVREF pins. The A/D converter has a unique feature of being able to operate while the device is in Sleep mode. To operate in Sleep, the A/D conversion clock must be derived from the A/D’s internal RC oscillator. The output of the sample and hold is the input into the converter, which generates the result via successive approximation. A device Reset forces all registers to their Reset state. This forces the A/D module to be turned off and any conversion in progress is aborted. Each port pin associated with the A/D converter can be configured as an analog input or as a digital I/O. The ADRESH and ADRESL registers contain the result of the A/D conversion. When the A/D conversion is complete, the result is loaded into the ADRESH:ADRESL register pair, the GO/DONE bit (ADCON0 register) is cleared and A/D Interrupt Flag bit, ADIF, is set. The block diagram of the A/D module is shown in Figure 21-1. FIGURE 21-1: A/D BLOCK DIAGRAM (Input Voltage) VAIN VREF+ Reference Voltage VDD(2) VCFG1:VCFG0 CHS3:CHS0 AN7(1) AN6(1) AN5(1) AN4 AN3 AN2 AN1 AN0 0111 0110 0101 0100 0011 0010 0001 0000 10-Bit Converter VREFVSS( 2) A/D AN12 AN11 AN10 AN9 AN8 1100 1011 1010 1001 1000 Note 1: Channels AN5 through AN7 are not available on 28-pin devices. 2: I/O pins have diode protection to VDD and VSS. 0X 1X X1 X0 © 2009 Microchip Technology Inc. DS39632E-page 269 PIC18F2455/2550/4455/4550 The value in the ADRESH:ADRESL registers is unknown following POR and BOR Resets and is not affected by any other Reset. After the A/D module has been configured as desired, the selected channel must be acquired before the conversion is started. The analog input channels must have their corresponding TRIS bits selected as an input. To determine acquisition time, see Section 21.1 “A/D Acquisition Requirements”. After this acquisition time has elapsed, the A/D conversion can be started. An acquisition time can be programmed to occur between setting the GO/DONE bit and the actual start of the conversion. The following steps should be followed to perform an A/D conversion: 1. Configure the A/D module: • Configure analog pins, voltage reference and digital I/O (ADCON1) • Select A/D input channel (ADCON0) • Select A/D acquisition time (ADCON2) • Select A/D conversion clock (ADCON2) • Turn on A/D module (ADCON0) 2. Configure A/D interrupt (if desired): • Clear ADIF bit • Set ADIE bit • Set GIE bit 3. Wait the required acquisition time (if required). 4. Start conversion: • Set GO/DONE bit (ADCON0 register) 5. Wait for A/D conversion to complete, by either: • Polling for the GO/DONE bit to be cleared OR • Waiting for the A/D interrupt 6. Read A/D Result registers (ADRESH:ADRESL); clear bit ADIF, if required. 7. For next conversion, go to step 1 or step 2, as required. The A/D conversion time per bit is defined as TAD. A minimum wait of 3 TAD is required before the next acquisition starts. FIGURE 21-2: A/D TRANSFER FUNCTION FIGURE 21-3: ANALOG INPUT MODEL Digital Code Output 3FEh 003h 002h 001h 000h 0.5 LSB 1 LSB 1.5 LSB 2 LSB 2.5 LSB 1022 LSB 1022.5 LSB 3 LSB Analog Input Voltage 3FFh 1023 LSB 1023.5 LSB VAIN CPIN Rs ANx 5 pF VT = 0.6V VT = 0.6V ILEAKAGE RIC ≤ 1k Sampling Switch SS RSS CHOLD = 25 pF VSS VDD ±100 nA Legend: CPIN VT ILEAKAGE RIC SS CHOLD = Input Capacitance = Threshold Voltage = Leakage Current at the pin due to = Interconnect Resistance = Sampling Switch = Sample/hold Capacitance (from DAC) various junctions RSS = Sampling Switch Resistance VDD 6V Sampling Switch 5V 4V 3V 2V 1 2 3 4 (kΩ) PIC18F2455/2550/4455/4550 DS39632E-page 270 © 2009 Microchip Technology Inc. 21.1 A/D Acquisition Requirements For the A/D converter to meet its specified accuracy, the charge holding capacitor (CHOLD) must be allowed to fully charge to the input channel voltage level. The analog input model is shown in Figure 21-3. The source impedance (RS) and the internal sampling switch (RSS) impedance directly affect the time required to charge the capacitor CHOLD. The sampling switch (RSS) impedance varies over the device voltage (VDD). The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ. After the analog input channel is selected (changed), the channel must be sampled for at least the minimum acquisition time before starting a conversion. To calculate the minimum acquisition time, Equation 21-1 may be used. This equation assumes that 1/2 LSb error is used (1024 steps for the A/D). The 1/2 LSb error is the maximum error allowed for the A/D to meet its specified resolution. Example 21-3 shows the calculation of the minimum required acquisition time TACQ. This calculation is based on the following application system assumptions: CHOLD = 25 pF Rs = 2.5 kΩ Conversion Error ≤ 1/2 LSb VDD = 5V → RSS = 2 kΩ Temperature = 85°C (system max.) EQUATION 21-1: ACQUISITION TIME EQUATION 21-2: A/D MINIMUM CHARGING TIME EQUATION 21-3: CALCULATING THE MINIMUM REQUIRED ACQUISITION TIME Note: When the conversion is started, the holding capacitor is disconnected from the input pin. TACQ = Amplifier Settling Time + Holding Capacitor Charging Time + Temperature Coefficient = TAMP + TC + TCOFF VHOLD = (VREF – (VREF/2048)) • (1 – e(-TC/CHOLD(RIC + RSS + RS))) or TC = -(CHOLD)(RIC + RSS + RS) ln(1/2048) TACQ = TAMP + TC + TCOFF TAMP = 0.2 μs TCOFF = (Temp – 25°C)(0.02 μs/°C) (85°C – 25°C)(0.02 μs/°C) 1.2 μs Temperature coefficient is only required for temperatures > 25°C. Below 25°C, TCOFF = 0 μs. TC = -(CHOLD)(RIC + RSS + RS) ln(1/2048) μs -(25 pF) (1 kΩ + 2 kΩ + 2.5 kΩ) ln(0.0004883) μs 1.05 μs TACQ = 0.2 μs + 1.05 μs + 1.2 μs 2.45 μs © 2009 Microchip Technology Inc. DS39632E-page 271 PIC18F2455/2550/4455/4550 21.2 Selecting and Configuring Acquisition Time The ADCON2 register allows the user to select an acquisition time that occurs each time the GO/DONE bit is set. It also gives users the option to use an automatically determined acquisition time. Acquisition time may be set with the ACQT2:ACQT0 bits (ADCON2<5:3>) which provide a range of 2 to 20 TAD. When the GO/DONE bit is set, the A/D module continues to sample the input for the selected acquisition time, then automatically begins a conversion. Since the acquisition time is programmed, there may be no need to wait for an acquisition time between selecting a channel and setting the GO/DONE bit. Manual acquisition is selected when ACQT2:ACQT0 = 000. When the GO/DONE bit is set, sampling is stopped and a conversion begins. The user is responsible for ensuring the required acquisition time has passed between selecting the desired input channel and setting the GO/DONE bit. This option is also the default Reset state of the ACQT2:ACQT0 bits and is compatible with devices that do not offer programmable acquisition times. In either case, when the conversion is completed, the GO/DONE bit is cleared, the ADIF flag is set and the A/D begins sampling the currently selected channel again. If an acquisition time is programmed, there is nothing to indicate if the acquisition time has ended or if the conversion has begun. 21.3 Selecting the A/D Conversion Clock The A/D conversion time per bit is defined as TAD. The A/D conversion requires 11 TAD per 10-bit conversion. The source of the A/D conversion clock is software selectable. There are seven possible options for TAD: • 2 TOSC • 4 TOSC • 8 TOSC • 16 TOSC • 32 TOSC • 64 TOSC • Internal RC Oscillator For correct A/D conversions, the A/D conversion clock (TAD) must be as short as possible but greater than the minimum TAD (see parameter 130 in Table 28-29 for more information). Table 21-1 shows the resultant TAD times derived from the device operating frequencies and the A/D clock source selected. TABLE 21-1: TAD vs. DEVICE OPERATING FREQUENCIES AD Clock Source (TAD) Assumes TAD Min. = 0.8 μs Operation ADCS2:ADCS0 Maximum FOSC 2 TOSC 000 2.50 MHz 4 TOSC 100 5.00 MHz 8 TOSC 001 10.00 MHz 16 TOSC 101 20.00 MHz 32 TOSC 010 40.00 MHz 64 TOSC 110 48.00 MHz RC(2) x11 1.00 MHz(1) Note 1: The RC source has a typical TAD time of 2.5 μs. 2: For device frequencies above 1 MHz, the device must be in Sleep for the entire conversion or a FOSC divider should be used instead. Otherwise, the A/D accuracy may be out of specification. PIC18F2455/2550/4455/4550 DS39632E-page 272 © 2009 Microchip Technology Inc. 21.4 Operation in Power-Managed Modes The selection of the automatic acquisition time and A/D conversion clock is determined in part by the clock source and frequency while in a power-managed mode. If the A/D is expected to operate while the device is in a power-managed mode, the ACQT2:ACQT0 and ADCS2:ADCS0 bits in ADCON2 should be updated in accordance with the clock source to be used in that mode. After entering the mode, an A/D acquisition or conversion may be started. Once started, the device should continue to be clocked by the same clock source until the conversion has been completed. If desired, the device may be placed into the corresponding Idle mode during the conversion. If the device clock frequency is less than 1 MHz, the A/D RC clock source should be selected. Operation in the Sleep mode requires the A/D FRC clock to be selected. If bits ACQT2:ACQT0 are set to ‘000’ and a conversion is started, the conversion will be delayed one instruction cycle to allow execution of the SLEEP instruction and entry to Sleep mode. The IDLEN bit (OSCCON<7>) must have already been cleared prior to starting the conversion. 21.5 Configuring Analog Port Pins The ADCON1, TRISA, TRISB and TRISE registers all configure the A/D port pins. The port pins needed as analog inputs must have their corresponding TRIS bits set (input). If the TRIS bit is cleared (output), the digital output level (VOH or VOL) will be converted. The A/D operation is independent of the state of the CHS3:CHS0 bits and the TRIS bits. Note 1: When reading the PORT register, all pins configured as analog input channels will read as cleared (a low level). Pins configured as digital inputs will convert as analog inputs. Analog levels on a digitally configured input will be accurately converted. 2: Analog levels on any pin defined as a digital input may cause the digital input buffer to consume current out of the device’s specification limits. 3: The PBADEN bit in Configuration Register 3H configures PORTB pins to reset as analog or digital pins by controlling how the PCFG0 bits in ADCON1 are reset. © 2009 Microchip Technology Inc. DS39632E-page 273 PIC18F2455/2550/4455/4550 21.6 A/D Conversions Figure 21-4 shows the operation of the A/D converter after the GO/DONE bit has been set and the ACQT2:ACQT0 bits are cleared. A conversion is started after the following instruction to allow entry into Sleep mode before the conversion begins. Figure 21-5 shows the operation of the A/D converter after the GO/DONE bit has been set, the ACQT2:ACQT0 bits are set to ‘010’ and selecting a 4 TAD acquisition time before the conversion starts. Clearing the GO/DONE bit during a conversion will abort the current conversion. The A/D Result register pair will NOT be updated with the partially completed A/D conversion sample. This means the ADRESH:ADRESL registers will continue to contain the value of the last completed conversion (or the last value written to the ADRESH:ADRESL registers). After the A/D conversion is completed or aborted, a 2 TCY wait is required before the next acquisition can be started. After this wait, acquisition on the selected channel is automatically started. 21.7 Discharge The discharge phase is used to initialize the value of the capacitor array. The array is discharged before every sample. This feature helps to optimize the unity-gain amplifier as the circuit always needs to charge the capacitor array, rather than charge/discharge based on previous measurement values. FIGURE 21-4: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0) FIGURE 21-5: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD) Note: The GO/DONE bit should NOT be set in the same instruction that turns on the A/D. Code should wait at least 2 μs after enabling the A/D before beginning an acquisition and conversion cycle. TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD11 Set GO/DONE bit Holding capacitor is disconnected from analog input (typically 100 ns) TCY - TAD TAD9 TAD10 ADRESH:ADRESL is loaded, GO/DONE bit is cleared, ADIF bit is set, holding capacitor is connected to analog input. Conversion starts b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 On the following cycle: TAD1 Discharge (Typically 200 ns) 1 2 3 4 5 6 7 8 11 Set GO/DONE bit (Holding capacitor is disconnected) 9 10 Conversion starts 1 2 3 4 (Holding capacitor continues acquiring input) TACQ Cycles TAD Cycles Automatic Acquisition Time b9 b8 b7 b6 b5 b4 b3 b2 b1 b0 ADRESH:ADRESL is loaded, GO/DONE bit is cleared, ADIF bit is set, holding capacitor is connected to analog input. On the following cycle: TAD1 Discharge (Typically 200 ns) PIC18F2455/2550/4455/4550 DS39632E-page 274 © 2009 Microchip Technology Inc. 21.8 Use of the CCP2 Trigger An A/D conversion can be started by the Special Event Trigger of the CCP2 module. This requires that the CCP2M3:CCP2M0 bits (CCP2CON<3:0>) be programmed as ‘1011’ and that the A/D module is enabled (ADON bit is set). When the trigger occurs, the GO/DONE bit will be set, starting the A/D acquisition and conversion and the Timer1 (or Timer3) counter will be reset to zero. Timer1 (or Timer3) is reset to automatically repeat the A/D acquisition period with minimal software overhead (moving ADRESH:ADRESL to the desired location). The appropriate analog input channel must be selected and the minimum acquisition period is either timed by the user, or an appropriate TACQ time selected before the Special Event Trigger sets the GO/DONE bit (starts a conversion). If the A/D module is not enabled (ADON is cleared), the Special Event Trigger will be ignored by the A/D module but will still reset the Timer1 (or Timer3) counter. TABLE 21-2: REGISTERS ASSOCIATED WITH A/D OPERATION Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR1 SPPIF(4) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 56 PIE1 SPPIE(4) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 56 IPR1 SPPIP(4) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 56 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 ADRESH A/D Result Register High Byte 54 ADRESL A/D Result Register Low Byte 54 ADCON0 — — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON 54 ADCON1 — — VCFG1 VCFG0 PCFG3 PCFG2 PCFG1 PCFG0 54 ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 54 PORTA — RA6(2) RA5 RA4 RA3 RA2 RA1 RA0 56 TRISA — TRISA6(2) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 56 TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 56 LATB LATB7 LATB6 LATB5 LATB4 LATB3 LATB2 LATB1 LATB0 56 PORTE RDPU(4) — — — RE3(1,3) RE2(4) RE1(4) RE0(4) 56 TRISE(4) — — — — — TRISE2 TRISE1 TRISE0 56 LATE(4) — — — — — LATE2 LATE1 LATE0 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion. Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0). 2: RA6 and its associated latch and data direction bits are enabled as I/O pins based on oscillator configuration; otherwise, they are read as ‘0’. 3: RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’. 4: These registers and/or bits are not implemented on 28-pin devices. © 2009 Microchip Technology Inc. DS39632E-page 275 PIC18F2455/2550/4455/4550 22.0 COMPARATOR MODULE The analog comparator module contains two comparators that can be configured in a variety of ways. The inputs can be selected from the analog inputs multiplexed with pins RA0 through RA5, as well as the on-chip voltage reference (see Section 23.0 “Comparator Voltage Reference Module”). The digital outputs (normal or inverted) are available at the pin level and can also be read through the control register. The CMCON register (Register 22-1) selects the comparator input and output configuration. Block diagrams of the various comparator configurations are shown in Figure 22-1. REGISTER 22-1: CMCON: COMPARATOR CONTROL REGISTER R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1 C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 C2OUT: Comparator 2 Output bit When C2INV = 0: 1 = C2 VIN+ > C2 VIN- 0 = C2 VIN+ < C2 VINWhen C2INV = 1: 1 = C2 VIN+ < C2 VIN- 0 = C2 VIN+ > C2 VINbit 6 C1OUT: Comparator 1 Output bit When C1INV = 0: 1 = C1 VIN+ > C1 VIN- 0 = C1 VIN+ < C1 VINWhen C1INV = 1: 1 = C1 VIN+ < C1 VIN- 0 = C1 VIN+ > C1 VINbit 5 C2INV: Comparator 2 Output Inversion bit 1 = C2 output inverted 0 = C2 output not inverted bit 4 C1INV: Comparator 1 Output Inversion bit 1 = C1 output inverted 0 = C1 output not inverted bit 3 CIS: Comparator Input Switch bit When CM2:CM0 = 110: 1 = C1 VIN- connects to RA3/AN3/VREF+ C2 VIN- connects to RA2/AN2/VREF-/CVREF 0 = C1 VIN- connects to RA0/AN0 C2 VIN- connects to RA1/AN1 bit 2-0 CM2:CM0: Comparator Mode bits Figure 22-1 shows the Comparator modes and the CM2:CM0 bit settings. PIC18F2455/2550/4455/4550 DS39632E-page 276 © 2009 Microchip Technology Inc. 22.1 Comparator Configuration There are eight modes of operation for the comparators, shown in Figure 22-1. Bits, CM2:CM0 of the CMCON register, are used to select these modes. The TRISA register controls the data direction of the comparator pins for each mode. If the Comparator mode is changed, the comparator output level may not be valid for the specified mode change delay shown in Section 28.0 “Electrical Characteristics”. FIGURE 22-1: COMPARATOR I/O OPERATING MODES Note: Comparator interrupts should be disabled during a Comparator mode change. Otherwise, a false interrupt may occur. C1 RA0/AN0 VINRA3/ AN3/ VIN+ Off (Read as ‘0’) Comparators Reset A A CM2:CM0 = 000 C2 RA1/AN1 VINRA2/ AN2/ VIN+ Off (Read as ‘0’) A A C1 VINVIN+ C1OUT Two Independent Comparators A A CM2:CM0 = 010 C2 VINVIN+ C2OUT A A C1 VINVIN+ C1OUT Two Common Reference Comparators A A CM2:CM0 = 100 C2 VINVIN+ C2OUT A D C2 VINVIN+ Off (Read as ‘0’) One Independent Comparator with Output D D CM2:CM0 = 001 C1 VINVIN+ C1OUT A A C1 VINVIN+ Off (Read as ‘0’) Comparators Off (POR Default Value) D D CM2:CM0 = 111 C2 VINVIN+ Off (Read as ‘0’) D D C1 VINVIN+ C1OUT Four Inputs Multiplexed to Two Comparators A A CM2:CM0 = 110 C2 VINVIN+ C2OUT A A From VREF Module CIS = 0 CIS = 1 CIS = 0 CIS = 1 C1 VINVIN+ C1OUT Two Common Reference Comparators with Outputs A A CM2:CM0 = 101 C2 VINVIN+ C2OUT A D A = Analog Input, port reads zeros always D = Digital Input CIS (CMCON<3>) is the Comparator Input Switch CVREF C1 VINVIN+ C1OUT Two Independent Comparators with Outputs A A CM2:CM0 = 011 C2 VINVIN+ C2OUT A A RA5/AN4/SS/HLVDIN/C2OUT* RA4/T0CKI/C1OUT*/RCV VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ RA1/AN1 RA2/AN2/ VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ RA1/AN1 RA2/AN2/ VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ RA1/AN1 RA2/AN2/ VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ RA1/AN1 RA2/AN2/ VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ RA1/AN1 RA2/AN2/ VREF+ VREF-/CVREF RA0/AN0 RA3/AN3/ VREF+ RA1/AN1 RA2/AN2/ VREF-/CVREF RA4/T0CKI/C1OUT*/RCV RA5/AN4/SS/HLVDIN/C2OUT* RA0/AN0 RA3/AN3/ VREF+ RA1/AN1 RA2/AN2/ VREF-/CVREF RA4/T0CKI/C1OUT*/ * Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs. RCV © 2009 Microchip Technology Inc. DS39632E-page 277 PIC18F2455/2550/4455/4550 22.2 Comparator Operation A single comparator is shown in Figure 22-2, along with the relationship between the analog input levels and the digital output. When the analog input at VIN+ is less than the analog input VIN-, the output of the comparator is a digital low level. When the analog input at VIN+ is greater than the analog input VIN-, the output of the comparator is a digital high level. The shaded areas of the output of the comparator in Figure 22-2 represent the uncertainty, due to input offsets and response time. 22.3 Comparator Reference Depending on the comparator operating mode, either an external or internal voltage reference may be used. The analog signal present at VIN- is compared to the signal at VIN+ and the digital output of the comparator is adjusted accordingly (Figure 22-2). FIGURE 22-2: SINGLE COMPARATOR 22.3.1 EXTERNAL REFERENCE SIGNAL When external voltage references are used, the comparator module can be configured to have the comparators operate from the same or different reference sources. However, threshold detector applications may require the same reference. The reference signal must be between VSS and VDD and can be applied to either pin of the comparator(s). 22.3.2 INTERNAL REFERENCE SIGNAL The comparator module also allows the selection of an internally generated voltage reference from the comparator voltage reference module. This module is described in more detail in Section 23.0 “Comparator Voltage Reference Module”. The internal reference is only available in the mode where four inputs are multiplexed to two comparators (CM2:CM0 = 110). In this mode, the internal voltage reference is applied to the VIN+ pin of both comparators. 22.4 Comparator Response Time Response time is the minimum time, after selecting a new reference voltage or input source, before the comparator output has a valid level. If the internal reference is changed, the maximum delay of the internal voltage reference must be considered when using the comparator outputs. Otherwise, the maximum delay of the comparators should be used (see Section 28.0 “Electrical Characteristics”). 22.5 Comparator Outputs The comparator outputs are read through the CMCON register. These bits are read-only. The comparator outputs may also be directly output to the RA4 and RA5 I/O pins. When enabled, multiplexors in the output path of the RA4 and RA5 pins will switch and the output of each pin will be the unsynchronized output of the comparator. The uncertainty of each of the comparators is related to the input offset voltage and the response time given in the specifications. Figure 22-3 shows the comparator output block diagram. The TRISA bits will still function as an output enable/ disable for the RA4 and RA5 pins while in this mode. The polarity of the comparator outputs can be changed using the C2INV and C1INV bits (CMCON<5:4>). – VIN+ + VINOutput Output VINVIN+ Note 1: When reading the PORT register, all pins configured as analog inputs will read as a ‘0’. Pins configured as digital inputs will convert an analog input according to the Schmitt Trigger input specification. 2: Analog levels on any pin defined as a digital input may cause the input buffer to consume more current than is specified. PIC18F2455/2550/4455/4550 DS39632E-page 278 © 2009 Microchip Technology Inc. FIGURE 22-3: COMPARATOR OUTPUT BLOCK DIAGRAM 22.6 Comparator Interrupts The comparator interrupt flag is set whenever there is a change in the output value of either comparator. Software will need to maintain information about the status of the output bits, as read from CMCON<7:6>, to determine the actual change that occurred. The CMIF bit (PIR2<6>) is the Comparator Interrupt Flag. The CMIF bit must be reset by clearing it. Since it is also possible to write a ‘1’ to this register, a simulated interrupt may be initiated. Both the CMIE bit (PIE2<6>) and the PEIE bit (INTCON< 6>) must be set to enable the interrupt. In addition, the GIE bit (INTCON<7>) must also be set. If any of these bits are clear, the interrupt is not enabled, though the CMIF bit will still be set if an interrupt condition occurs. The user, in the Interrupt Service Routine, can clear the interrupt in the following manner: a) Any read or write of CMCON will end the mismatch condition. b) Clear flag bit CMIF. A mismatch condition will continue to set flag bit CMIF. Reading CMCON will end the mismatch condition and allow flag bit CMIF to be cleared. 22.7 Comparator Operation During Sleep When a comparator is active and the device is placed in Sleep mode, the comparator remains active and the interrupt is functional if enabled. This interrupt will wake-up the device from Sleep mode, when enabled. Each operational comparator will consume additional current, as shown in the comparator specifications. To minimize power consumption while in Sleep mode, turn off the comparators (CM2:CM0 = 111) before entering Sleep. If the device wakes up from Sleep, the contents of the CMCON register are not affected. 22.8 Effects of a Reset A device Reset forces the CMCON register to its Reset state, causing the comparator modules to be turned off (CM2:CM0 = 111). However, the input pins (RA0 through RA3) are configured as analog inputs by default on device Reset. The I/O configuration for these pins is determined by the setting of the PCFG3:PCFG0 bits (ADCON1<3:0>). Therefore, device current is minimized when analog inputs are present at Reset time. D Q EN To CxOUT pin Bus Data Set MULTIPLEX CMIF bit + Port Pins Read CMCON Reset From Other Comparator CxINV D Q EN CL - Note: If a change in the CMCON register (C1OUT or C2OUT) should occur when a read operation is being executed (start of the Q2 cycle), then the CMIF (PIR2<6>) interrupt flag may not get set. © 2009 Microchip Technology Inc. DS39632E-page 279 PIC18F2455/2550/4455/4550 22.9 Analog Input Connection Considerations A simplified circuit for an analog input is shown in Figure 22-4. Since the analog pins are connected to a digital output, they have reverse biased diodes to VDD and VSS. The analog input, therefore, must be between VSS and VDD. If the input voltage deviates from this range by more than 0.6V in either direction, one of the diodes is forward biased and a latch-up condition may occur. A maximum source impedance of 10 kΩ is recommended for the analog sources. Any external component connected to an analog input pin, such as a capacitor or a Zener diode, should have very little leakage current. FIGURE 22-4: COMPARATOR ANALOG INPUT MODEL TABLE 22-1: REGISTERS ASSOCIATED WITH COMPARATOR MODULE VA RS < 10k AIN CPIN 5 pF VDD VT = 0.6V VT = 0.6V RIC ILEAKAGE ±500 nA VSS Legend: CPIN = Input Capacitance VT = Threshold Voltage ILEAKAGE = Leakage Current at the pin due to various junctions RIC = Interconnect Resistance RS = Source Impedance VA = Analog Voltage Comparator Input Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 55 CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 55 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 PORTA — RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 56 LATA — LATA6(1) LATA5 LATA4 LATA3 LATA2 LATA1 LATA0 56 TRISA — TRISA6(1) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module. Note 1: PORTA<6> and its direction and latch bits are individually configured as port pins based on various oscillator modes. When disabled, these bits read as ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 280 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 281 PIC18F2455/2550/4455/4550 23.0 COMPARATOR VOLTAGE REFERENCE MODULE The comparator voltage reference is a 16-tap resistor ladder network that provides a selectable reference voltage. Although its primary purpose is to provide a reference for the analog comparators, it may also be used independently of them. A block diagram of the module is shown in Figure 23-1. The resistor ladder is segmented to provide two ranges of CVREF values and has a power-down function to conserve power when the reference is not being used. The module’s supply reference can be provided from either device VDD/VSS or an external voltage reference. 23.1 Configuring the Comparator Voltage Reference The voltage reference module is controlled through the CVRCON register (Register 23-1). The comparator voltage reference provides two ranges of output voltage, each with 16 distinct levels. The range to be used is selected by the CVRR bit (CVRCON<5>). The primary difference between the ranges is the size of the steps selected by the CVREF Selection bits (CVR3:CVR0), with one range offering finer resolution. The equations used to calculate the output of the comparator voltage reference are as follows: If CVRR = 1: CVREF = ((CVR3:CVR0)/24) x CVRSRC If CVRR = 0: CVREF = (CVRSRC/4) + (((CVR3:CVR0)/32) x CVRSRC) The comparator reference supply voltage can come from either VDD and VSS, or the external VREF+ and VREF- that are multiplexed with RA2 and RA3. The voltage source is selected by the CVRSS bit (CVRCON<4>). The settling time of the comparator voltage reference must be considered when changing the CVREF output (see Table 28-3 in Section 28.0 “Electrical Characteristics”). REGISTER 23-1: CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 CVREN CVROE(1) CVRR CVRSS CVR3 CVR2 CVR1 CVR0 bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 CVREN: Comparator Voltage Reference Enable bit 1 = CVREF circuit powered on 0 = CVREF circuit powered down bit 6 CVROE: Comparator VREF Output Enable bit(1) 1 = CVREF voltage level is also output on the RA2/AN2/VREF-/CVREF pin 0 = CVREF voltage is disconnected from the RA2/AN2/VREF-/CVREF pin bit 5 CVRR: Comparator VREF Range Selection bit 1 = 0 to 0.667 CVRSRC, with CVRSRC/24 step size (low range) 0 = 0.25 CVRSRC to 0.75 CVRSRC, with CVRSRC/32 step size (high range) bit 4 CVRSS: Comparator VREF Source Selection bit 1 = Comparator reference source, CVRSRC = (VREF+) – (VREF-) 0 = Comparator reference source, CVRSRC = VDD – VSS bit 3-0 CVR3:CVR0: Comparator VREF Value Selection bits (0 ≤ (CVR3:CVR0) ≤ 15) When CVRR = 1: CVREF = ((CVR3:CVR0)/24) • (CVRSRC) When CVRR = 0: CVREF = (CVRSRC/4) + ((CVR3:CVR0)/32) • (CVRSRC) Note 1: CVROE overrides the TRISA<2> bit setting. PIC18F2455/2550/4455/4550 DS39632E-page 282 © 2009 Microchip Technology Inc. FIGURE 23-1: COMPARATOR VOLTAGE REFERENCE BLOCK DIAGRAM 23.2 Voltage Reference Accuracy/Error The full range of voltage reference cannot be realized due to the construction of the module. The transistors on the top and bottom of the resistor ladder network (Figure 23-1) keep CVREF from approaching the reference source rails. The voltage reference is derived from the reference source; therefore, the CVREF output changes with fluctuations in that source. The tested absolute accuracy of the voltage reference can be found in Section 28.0 “Electrical Characteristics”. 23.3 Operation During Sleep When the device wakes up from Sleep through an interrupt or a Watchdog Timer time-out, the contents of the CVRCON register are not affected. To minimize current consumption in Sleep mode, the voltage reference should be disabled. 23.4 Effects of a Reset A device Reset disables the voltage reference by clearing bit, CVREN (CVRCON<7>). This Reset also disconnects the reference from the RA2 pin by clearing bit, CVROE (CVRCON<6>) and selects the high-voltage range by clearing bit, CVRR (CVRCON<5>). The CVR value select bits are also cleared. 23.5 Connection Considerations The voltage reference module operates independently of the comparator module. The output of the reference generator may be connected to the RA2 pin if the TRISA<2> bit and the CVROE bit are both set. Enabling the voltage reference output onto RA2 when it is configured as a digital input will increase current consumption. Connecting RA2 as a digital output with CVRSS enabled will also increase current consumption. The RA2 pin can be used as a simple D/A output with limited drive capability. Due to the limited current drive capability, a buffer must be used on the voltage reference output for external connections to VREF. Figure 23-2 shows an example buffering technique. 16-to-1 MUX CVR3:CVR0 8R CVREN R CVRSS = 0 VDD VREF+ CVRSS = 1 8R CVRSS = 0 VREFCVRSS = 1 R R R R R R 16 Steps CVRR CVREF © 2009 Microchip Technology Inc. DS39632E-page 283 PIC18F2455/2550/4455/4550 FIGURE 23-2: COMPARATOR VOLTAGE REFERENCE OUTPUT BUFFER EXAMPLE TABLE 23-1: REGISTERS ASSOCIATED WITH COMPARATOR VOLTAGE REFERENCE CVREF Output +– CVREF Module Voltage Reference Output Impedance R(1) RA2 Note 1: R is dependent upon the voltage reference configuration bits, CVRCON<5> and CVRCON<3:0>. PIC18FXXXX Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 55 CMCON C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0 55 TRISA — TRISA6(1) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 56 Legend: Shaded cells are not used with the comparator voltage reference. Note 1: PORTA<6> and its direction and latch bits are individually configured as port pins based on various oscillator modes. When disabled, these bits read as ‘0’. PIC18F2455/2550/4455/4550 DS39632E-page 284 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 285 PIC18F2455/2550/4455/4550 24.0 HIGH/LOW-VOLTAGE DETECT (HLVD) PIC18F2455/2550/4455/4550 devices have a High/Low-Voltage Detect module (HLVD). This is a programmable circuit that allows the user to specify both a device voltage trip point and the direction of change from that point. If the device experiences an excursion past the trip point in that direction, an interrupt flag is set. If the interrupt is enabled, the program execution will branch to the interrupt vector address and the software can then respond to the interrupt. The High/Low-Voltage Detect Control register (Register 24-1) completely controls the operation of the HLVD module. This allows the circuitry to be “turned off” by the user under software control which minimizes the current consumption for the device. The block diagram for the HLVD module is shown in Figure 24-1. REGISTER 24-1: HLVDCON: HIGH/LOW-VOLTAGE DETECT CONTROL REGISTER R/W-0 U-0 R-0 R/W-0 R/W-0 R/W-1 R/W-0 R/W-1 VDIRMAG — IRVST HLVDEN HLVDL3(1) HLVDL2(1) HLVDL1(1) HLVDL0(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7 VDIRMAG: Voltage Direction Magnitude Select bit 1 = Event occurs when voltage equals or exceeds trip point (HLVDL3:HLDVL0) 0 = Event occurs when voltage equals or falls below trip point (HLVDL3:HLVDL0) bit 6 Unimplemented: Read as ‘0’ bit 5 IRVST: Internal Reference Voltage Stable Flag bit 1 = Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage range 0 = Indicates that the voltage detect logic will not generate the interrupt flag at the specified voltage range and the HLVD interrupt should not be enabled bit 4 HLVDEN: High/Low-Voltage Detect Power Enable bit 1 = HLVD enabled 0 = HLVD disabled bit 3-0 HLVDL3:HLVDL0: Voltage Detection Limit bits(1) 1111 = External analog input is used (input comes from the HLVDIN pin) 1110 = Maximum setting . . . 0000 = Minimum setting Note 1: See Table 28-6 in Section 28.0 “Electrical Characteristics” for specifications. PIC18F2455/2550/4455/4550 DS39632E-page 286 © 2009 Microchip Technology Inc. The module is enabled by setting the HLVDEN bit. Each time that the HLVD module is enabled, the circuitry requires some time to stabilize. The IRVST bit is a read-only bit and is used to indicate when the circuit is stable. The module can only generate an interrupt after the circuit is stable and IRVST is set. The VDIRMAG bit determines the overall operation of the module. When VDIRMAG is cleared, the module monitors for drops in VDD below a predetermined set point. When the bit is set, the module monitors for rises in VDD above the set point. 24.1 Operation When the HLVD module is enabled, a comparator uses an internally generated reference voltage as the set point. The set point is compared with the trip point, where each node in the resistor divider represents a trip point voltage. The “trip point” voltage is the voltage level at which the device detects a high or low-voltage event, depending on the configuration of the module. When the supply voltage is equal to the trip point, the voltage tapped off of the resistor array is equal to the internal reference voltage generated by the voltage reference module. The comparator then generates an interrupt signal by setting the HLVDIF bit. The trip point voltage is software programmable to any one of 16 values. The trip point is selected by programming the HLVDL3:HLVDL0 bits (HLVDCON<3:0>). The HLVD module has an additional feature that allows the user to supply the trip voltage to the module from an external source. This mode is enabled when bits, HLVDL3:HLVDL0, are set to ‘1111’. In this state, the comparator input is multiplexed from the external input pin, HLVDIN. This gives users flexibility because it allows them to configure the High/Low-Voltage Detect interrupt to occur at any voltage in the valid operating range. FIGURE 24-1: HLVD MODULE BLOCK DIAGRAM (WITH EXTERNAL INPUT) Set VDD 16-to-1 MUX HLVDEN HLVDL3:HLVDL0 HLVDCON Register HLVDIN VDD Externally Generated Trip Point HLVDIF HLVDEN BOREN Internal Voltage Reference VDIRMAG 1.2V Typical © 2009 Microchip Technology Inc. DS39632E-page 287 PIC18F2455/2550/4455/4550 24.2 HLVD Setup The following steps are needed to set up the HLVD module: 1. Disable the module by clearing the HLVDEN bit (HLVDCON<4>). 2. Write the value to the HLVDL3:HLVDL0 bits that selects the desired HLVD trip point. 3. Set the VDIRMAG bit to detect high voltage (VDIRMAG = 1) or low voltage (VDIRMAG = 0). 4. Enable the HLVD module by setting the HLVDEN bit. 5. Clear the HLVD Interrupt Flag, HLVDIF (PIR2<2>), which may have been set from a previous interrupt. 6. Enable the HLVD interrupt, if interrupts are desired, by setting the HLVDIE and GIE/GIEH bits (PIE2<2> and INTCON<7>). An interrupt will not be generated until the IRVST bit is set. 24.3 Current Consumption When the module is enabled, the HLVD comparator and voltage divider are enabled and will consume static current. The total current consumption, when enabled, is specified in electrical specification parameter D022 (Section 28.2 “DC Characteristics”). Depending on the application, the HLVD module does not need to be operating constantly. To decrease the current requirements, the HLVD circuitry may only need to be enabled for short periods where the voltage is checked. After doing the check, the HLVD module may be disabled. 24.4 HLVD Start-up Time The internal reference voltage of the HLVD module, specified in electrical specification parameter D420 (see Table 28-6 in Section 28.0 “Electrical Characteristics”), may be used by other internal circuitry, such as the Programmable Brown-out Reset. If the HLVD or other circuits using the voltage reference are disabled to lower the device’s current consumption, the reference voltage circuit will require time to become stable before a low or high-voltage condition can be reliably detected. This start-up time, TIRVST, is an interval that is independent of device clock speed. It is specified in electrical specification parameter 36 (Table 28-12). The HLVD interrupt flag is not enabled until TIRVST has expired and a stable reference voltage is reached. For this reason, brief excursions beyond the set point may not be detected during this interval. Refer to Figure 24-2 or Figure 24-3. FIGURE 24-2: LOW-VOLTAGE DETECT OPERATION (VDIRMAG = 0) VHLVD VDD HLVDIF VHLVD VDD Enable HLVD TIRVST HLVDIF may not be set Enable HLVD HLVDIF HLVDIF cleared in software HLVDIF cleared in software HLVDIF cleared in software, CASE 1: CASE 2: HLVDIF remains set since HLVD condition still exists TIRVST Internal Reference is stable Internal Reference is stable IRVST IRVST PIC18F2455/2550/4455/4550 DS39632E-page 288 © 2009 Microchip Technology Inc. FIGURE 24-3: HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1) 24.5 Applications In many applications, the ability to detect a drop below or rise above a particular threshold is desirable. For example, the HLVD module could be periodically enabled to detect Universal Serial Bus (USB) attach or detach. This assumes the device is powered by a lower voltage source than the USB when detached. An attach would indicate a high-voltage detect from, for example, 3.3V to 5V (the voltage on USB) and vice versa for a detach. This feature could save a design a few extra components and an attach signal (input pin). For general battery applications, Figure 24-4 shows a possible voltage curve. Over time, the device voltage decreases. When the device voltage reaches voltage, VA, the HLVD logic generates an interrupt at time, TA. The interrupt could cause the execution of an ISR, which would allow the application to perform “housekeeping tasks” and perform a controlled shutdown before the device voltage exits the valid operating range at TB. The HLVD, thus, would give the application a time window, represented by the difference between TA and TB, to safely exit. FIGURE 24-4: TYPICAL HIGH/LOW-VOLTAGE DETECT APPLICATION VHLVD VDD HLVDIF VHLVD VDD Enable HLVD TIRVST HLVDIF may not be set Enable HLVD HLVDIF HLVDIF cleared in software HLVDIF cleared in software HLVDIF cleared in software, CASE 1: CASE 2: HLVDIF remains set since HLVD condition still exists TIRVST IRVST Internal Reference is stable Internal Reference is stable IRVST Time Voltage VA VB TA TB VA = HLVD trip point VB = Minimum valid device operating voltage Legend: © 2009 Microchip Technology Inc. DS39632E-page 289 PIC18F2455/2550/4455/4550 24.6 Operation During Sleep When enabled, the HLVD circuitry continues to operate during Sleep. If the device voltage crosses the trip point, the HLVDIF bit will be set and the device will wake-up from Sleep. Device execution will continue from the interrupt vector address if interrupts have been globally enabled. 24.7 Effects of a Reset A device Reset forces all registers to their Reset state. This forces the HLVD module to be turned off. TABLE 24-1: REGISTERS ASSOCIATED WITH HIGH/LOW-VOLTAGE DETECT MODULE Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 54 INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 53 PIR2 OSCFIF CMIF USBIF EEIF BCLIF HLVDIF TMR3IF CCP2IF 56 PIE2 OSCFIE CMIE USBIE EEIE BCLIE HLVDIE TMR3IE CCP2IE 56 IPR2 OSCFIP CMIP USBIP EEIP BCLIP HLVDIP TMR3IP CCP2IP 56 Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the HLVD module. PIC18F2455/2550/4455/4550 DS39632E-page 290 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 291 PIC18F2455/2550/4455/4550 25.0 SPECIAL FEATURES OF THE CPU PIC18F2455/2550/4455/4550 devices include several features intended to maximize reliability and minimize cost through elimination of external components. These are: • Oscillator Selection • Resets: - Power-on Reset (POR) - Power-up Timer (PWRT) - Oscillator Start-up Timer (OST) - Brown-out Reset (BOR) • Interrupts • Watchdog Timer (WDT) • Fail-Safe Clock Monitor • Two-Speed Start-up • Code Protection • ID Locations • In-Circuit Serial Programming The oscillator can be configured for the application depending on frequency, power, accuracy and cost. All of the options are discussed in detail in Section 2.0 “Oscillator Configurations”. A complete discussion of device Resets and interrupts is available in previous sections of this data sheet. In addition to their Power-up and Oscillator Start-up Timers provided for Resets, PIC18F2455/2550/4455/4550 devices have a Watchdog Timer, which is either permanently enabled via the Configuration bits or software controlled (if configured as disabled). The inclusion of an internal RC oscillator also provides the additional benefits of a Fail-Safe Clock Monitor (FSCM) and Two-Speed Start-up. FSCM provides for background monitoring of the peripheral clock and automatic switchover in the event of its failure. Two-Speed Start-up enables code to be executed almost immediately on start-up, while the primary clock source completes its start-up delays. All of these features are enabled and configured by setting the appropriate Configuration register bits. PIC18F2455/2550/4455/4550 DS39632E-page 292 © 2009 Microchip Technology Inc. 25.1 Configuration Bits The Configuration bits can be programmed (read as ‘0’) or left unprogrammed (read as ‘1’) to select various device configurations. These bits are mapped starting at program memory location 300000h. The user will note that address 300000h is beyond the user program memory space. In fact, it belongs to the configuration memory space (300000h-3FFFFFh), which can only be accessed using table reads and table writes. Programming the Configuration registers is done in a manner similar to programming the Flash memory. The WR bit in the EECON1 register starts a self-timed write to the Configuration register. In normal operation mode, a TBLWT instruction, with the TBLPTR pointing to the Configuration register, sets up the address and the data for the Configuration register write. Setting the WR bit starts a long write to the Configuration register. The Configuration registers are written a byte at a time. To write or erase a configuration cell, a TBLWT instruction can write a ‘1’ or a ‘0’ into the cell. For additional details on Flash programming, refer to Section 6.5 “Writing to Flash Program Memory”. TABLE 25-1: CONFIGURATION BITS AND DEVICE IDs File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Default/ Unprogrammed Value 300000h CONFIG1L — — USBDIV CPUDIV1 CPUDIV0 PLLDIV2 PLLDIV1 PLLDIV0 --00 0000 300001h CONFIG1H IESO FCMEN — — FOSC3 FOSC2 FOSC1 FOSC0 00-- 0101 300002h CONFIG2L — — VREGEN BORV1 BORV0 BOREN1 BOREN0 PWRTEN --01 1111 300003h CONFIG2H — — — WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN ---1 1111 300005h CONFIG3H MCLRE — — — — LPT1OSC PBADEN CCP2MX 1--- -011 300006h CONFIG4L DEBUG XINST ICPRT(3) — — LVP — STVREN 100- -1-1 300008h CONFIG5L — — — — CP3(1) CP2 CP1 CP0 ---- 1111 300009h CONFIG5H CPD CPB — — — — — — 11-- ---- 30000Ah CONFIG6L — — — — WRT3(1) WRT2 WRT1 WRT0 ---- 1111 30000Bh CONFIG6H WRTD WRTB WRTC — — — — — 111- ---- 30000Ch CONFIG7L — — — — EBTR3(1) EBTR2 EBTR1 EBTR0 ---- 1111 30000Dh CONFIG7H — EBTRB — — — — — — -1-- ---- 3FFFFEh DEVID1 DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0 xxxx xxxx(2) 3FFFFFh DEVID2 DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3 0001 0010(2) Legend: x = unknown, u = unchanged, - = unimplemented. Shaded cells are unimplemented, read as ‘0’. Note 1: Unimplemented in PIC18FX455 devices; maintain this bit set. 2: See Register 25-13 and Register 25-14 for DEVID values. DEVID registers are read-only and cannot be programmed by the user. 3: Available only on PIC18F4455/4550 devices in 44-pin TQFP packages. Always leave this bit clear in all other devices. © 2009 Microchip Technology Inc. DS39632E-page 293 PIC18F2455/2550/4455/4550 REGISTER 25-1: CONFIG1L: CONFIGURATION REGISTER 1 LOW (BYTE ADDRESS 300000h) U-0 U-0 R/P-0 R/P-0 R/P-0 R/P-0 R/P-0 R/P-0 — — USBDIV CPUDIV1 CPUDIV0 PLLDIV2 PLLDIV1 PLLDIV0 bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-6 Unimplemented: Read as ‘0’ bit 5 USBDIV: USB Clock Selection bit (used in Full-Speed USB mode only; UCFG:FSEN = 1) 1 = USB clock source comes from the 96 MHz PLL divided by 2 0 = USB clock source comes directly from the primary oscillator block with no postscale bit 4-3 CPUDIV1:CPUDIV0: System Clock Postscaler Selection bits For XT, HS, EC and ECIO Oscillator modes: 11 = Primary oscillator divided by 4 to derive system clock 10 = Primary oscillator divided by 3 to derive system clock 01 = Primary oscillator divided by 2 to derive system clock 00 = Primary oscillator used directly for system clock (no postscaler) For XTPLL, HSPLL, ECPLL and ECPIO Oscillator modes: 11 = 96 MHz PLL divided by 6 to derive system clock 10 = 96 MHz PLL divided by 4 to derive system clock 01 = 96 MHz PLL divided by 3 to derive system clock 00 = 96 MHz PLL divided by 2 to derive system clock bit 2-0 PLLDIV2:PLLDIV0: PLL Prescaler Selection bits 111 = Divide by 12 (48 MHz oscillator input) 110 = Divide by 10 (40 MHz oscillator input) 101 = Divide by 6 (24 MHz oscillator input) 100 = Divide by 5 (20 MHz oscillator input) 011 = Divide by 4 (16 MHz oscillator input) 010 = Divide by 3 (12 MHz oscillator input) 001 = Divide by 2 (8 MHz oscillator input) 000 = No prescale (4 MHz oscillator input drives PLL directly) PIC18F2455/2550/4455/4550 DS39632E-page 294 © 2009 Microchip Technology Inc. REGISTER 25-2: CONFIG1H: CONFIGURATION REGISTER 1 HIGH (BYTE ADDRESS 300001h) R/P-0 R/P-0 U-0 U-0 R/P-0 R/P-1 R/P-0 R/P-1 IESO FCMEN — — FOSC3(1) FOSC2(1) FOSC1(1) FOSC0(1) bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 IESO: Internal/External Oscillator Switchover bit 1 = Oscillator Switchover mode enabled 0 = Oscillator Switchover mode disabled bit 6 FCMEN: Fail-Safe Clock Monitor Enable bit 1 = Fail-Safe Clock Monitor enabled 0 = Fail-Safe Clock Monitor disabled bit 5-4 Unimplemented: Read as ‘0’ bit 3-0 FOSC3:FOSC0: Oscillator Selection bits(1) 111x = HS oscillator, PLL enabled (HSPLL) 110x = HS oscillator (HS) 1011 = Internal oscillator, HS oscillator used by USB (INTHS) 1010 = Internal oscillator, XT used by USB (INTXT) 1001 = Internal oscillator, CLKO function on RA6, EC used by USB (INTCKO) 1000 = Internal oscillator, port function on RA6, EC used by USB (INTIO) 0111 = EC oscillator, PLL enabled, CLKO function on RA6 (ECPLL) 0110 = EC oscillator, PLL enabled, port function on RA6 (ECPIO) 0101 = EC oscillator, CLKO function on RA6 (EC) 0100 = EC oscillator, port function on RA6 (ECIO) 001x = XT oscillator, PLL enabled (XTPLL) 000x = XT oscillator (XT) Note 1: The microcontroller and USB module both use the selected oscillator as their clock source in XT, HS and EC modes. The USB module uses the indicated XT, HS or EC oscillator as its clock source whenever the microcontroller uses the internal oscillator. © 2009 Microchip Technology Inc. DS39632E-page 295 PIC18F2455/2550/4455/4550 REGISTER 25-3: CONFIG2L: CONFIGURATION REGISTER 2 LOW (BYTE ADDRESS 300002h) U-0 U-0 R/P-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1 — — VREGEN BORV1(1) BORV0(1) BOREN1(2) BOREN0(2) PWRTEN(2) bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-6 Unimplemented: Read as ‘0’ bit 5 VREGEN: USB Internal Voltage Regulator Enable bit 1 = USB voltage regulator enabled 0 = USB voltage regulator disabled bit 4-3 BORV1:BORV0: Brown-out Reset Voltage bits(1) 11 = Minimum setting .. . 00 = Maximum setting bit 2-1 BOREN1:BOREN0: Brown-out Reset Enable bits(2) 11 = Brown-out Reset enabled in hardware only (SBOREN is disabled) 10 = Brown-out Reset enabled in hardware only and disabled in Sleep mode (SBOREN is disabled) 01 = Brown-out Reset enabled and controlled by software (SBOREN is enabled) 00 = Brown-out Reset disabled in hardware and software bit 0 PWRTEN: Power-up Timer Enable bit(2) 1 = PWRT disabled 0 = PWRT enabled Note 1: See Section 28.0 “Electrical Characteristics” for the specifications. 2: The Power-up Timer is decoupled from Brown-out Reset, allowing these features to be independently controlled. PIC18F2455/2550/4455/4550 DS39632E-page 296 © 2009 Microchip Technology Inc. REGISTER 25-4: CONFIG2H: CONFIGURATION REGISTER 2 HIGH (BYTE ADDRESS 300003h) U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1 — — — WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-5 Unimplemented: Read as ‘0’ bit 4-1 WDTPS3:WDTPS0: Watchdog Timer Postscale Select bits 1111 = 1:32,768 1110 = 1:16,384 1101 = 1:8,192 1100 = 1:4,096 1011 = 1:2,048 1010 = 1:1,024 1001 = 1:512 1000 = 1:256 0111 = 1:128 0110 = 1:64 0101 = 1:32 0100 = 1:16 0011 = 1:8 0010 = 1:4 0001 = 1:2 0000 = 1:1 bit 0 WDTEN: Watchdog Timer Enable bit 1 = WDT enabled 0 = WDT disabled (control is placed on the SWDTEN bit) © 2009 Microchip Technology Inc. DS39632E-page 297 PIC18F2455/2550/4455/4550 REGISTER 25-5: CONFIG3H: CONFIGURATION REGISTER 3 HIGH (BYTE ADDRESS 300005h) R/P-1 U-0 U-0 U-0 U-0 R/P-0 R/P-1 R/P-1 MCLRE — — — — LPT1OSC PBADEN CCP2MX bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 MCLRE: MCLR Pin Enable bit 1 = MCLR pin enabled, RE3 input pin disabled 0 = RE3 input pin enabled, MCLR pin disabled bit 6-3 Unimplemented: Read as ‘0’ bit 2 LPT1OSC: Low-Power Timer1 Oscillator Enable bit 1 = Timer1 configured for low-power operation 0 = Timer1 configured for higher power operation bit 1 PBADEN: PORTB A/D Enable bit (Affects ADCON1 Reset state. ADCON1 controls PORTB<4:0> pin configuration.) 1 = PORTB<4:0> pins are configured as analog input channels on Reset 0 = PORTB<4:0> pins are configured as digital I/O on Reset bit 0 CCP2MX: CCP2 MUX bit 1 = CCP2 input/output is multiplexed with RC1 0 = CCP2 input/output is multiplexed with RB3 PIC18F2455/2550/4455/4550 DS39632E-page 298 © 2009 Microchip Technology Inc. REGISTER 25-6: CONFIG4L: CONFIGURATION REGISTER 4 LOW (BYTE ADDRESS 300006h) R/P-1 R/P-0 R/P-0 U-0 U-0 R/P-1 U-0 R/P-1 DEBUG XINST ICPRT(1) — — LVP — STVREN bit 7 bit 0 Legend: R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 DEBUG: Background Debugger Enable bit 1 = Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins 0 = Background debugger enabled, RB6 and RB7 are dedicated to In-Circuit Debug bit 6 XINST: Extended Instruction Set Enable bit 1 = Instruction set extension and Indexed Addressing mode enabled 0 = Instruction set extension and Indexed Addressing mode disabled (Legacy mode) bit 5 ICPRT: Dedicated In-Circuit Debug/Programming Port (ICPORT) Enable bit(1) 1 = ICPORT enabled 0 = ICPORT disabled bit 4-3 Unimplemented: Read as ‘0’ bit 2 LVP: Single-Supply ICSP™ Enable bit 1 = Single-Supply ICSP enabled 0 = Single-Supply ICSP disabled bit 1 Unimplemented: Read as ‘0’ bit 0 STVREN: Stack Full/Underflow Reset Enable bit 1 = Stack full/underflow will cause Reset 0 = Stack full/underflow will not cause Reset Note 1: Available only in the 44-pin TQFP packages. Always leave this bit clear in all other devices. © 2009 Microchip Technology Inc. DS39632E-page 299 PIC18F2455/2550/4455/4550 REGISTER 25-7: CONFIG5L: CONFIGURATION REGISTER 5 LOW (BYTE ADDRESS 300008h) U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1 — — — — CP3(1) CP2 CP1 CP0 bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-4 Unimplemented: Read as ‘0’ bit 3 CP3: Code Protection bit(1) 1 = Block 3 (006000-007FFFh) is not code-protected 0 = Block 3 (006000-007FFFh) is code-protected bit 2 CP2: Code Protection bit 1 = Block 2 (004000-005FFFh) is not code-protected 0 = Block 2 (004000-005FFFh) is code-protected bit 1 CP1: Code Protection bit 1 = Block 1 (002000-003FFFh) is not code-protected 0 = Block 1 (002000-003FFFh) is code-protected bit 0 CP0: Code Protection bit 1 = Block 0 (000800-001FFFh) is not code-protected 0 = Block 0 (000800-001FFFh) is code-protected Note 1: Unimplemented in PIC18FX455 devices; maintain this bit set. REGISTER 25-8: CONFIG5H: CONFIGURATION REGISTER 5 HIGH (BYTE ADDRESS 300009h) R/C-1 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0 CPD CPB — — — — — — bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 CPD: Data EEPROM Code Protection bit 1 = Data EEPROM is not code-protected 0 = Data EEPROM is code-protected bit 6 CPB: Boot Block Code Protection bit 1 = Boot block (000000-0007FFh) is not code-protected 0 = Boot block (000000-0007FFh) is code-protected bit 5-0 Unimplemented: Read as ‘0’ PIC18F2455/2550/4455/4550 DS39632E-page 300 © 2009 Microchip Technology Inc. REGISTER 25-9: CONFIG6L: CONFIGURATION REGISTER 6 LOW (BYTE ADDRESS 30000Ah) U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1 — — — — WRT3(1) WRT2 WRT1 WRT0 bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-4 Unimplemented: Read as ‘0’ bit 3 WRT3: Write Protection bit(1) 1 = Block 3 (006000-007FFFh) is not write-protected 0 = Block 3 (006000-007FFFh) is write-protected bit 2 WRT2: Write Protection bit 1 = Block 2 (004000-005FFFh) is not write-protected 0 = Block 2 (004000-005FFFh) is write-protected bit 1 WRT1: Write Protection bit 1 = Block 1 (002000-003FFFh) is not write-protected 0 = Block 1 (002000-003FFFh) is write-protected bit 0 WRT0: Write Protection bit 1 = Block 0 (000800-001FFFh) or (001000-001FFFh) is not write-protected 0 = Block 0 (000800-001FFFh) or (001000-001FFFh) is write-protected Note 1: Unimplemented in PIC18FX455 devices; maintain this bit set. REGISTER 25-10: CONFIG6H: CONFIGURATION REGISTER 6 HIGH (BYTE ADDRESS 30000Bh) R/C-1 R/C-1 R-1 U-0 U-0 U-0 U-0 U-0 WRTD WRTB WRTC(1) — — — — — bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 WRTD: Data EEPROM Write Protection bit 1 = Data EEPROM is not write-protected 0 = Data EEPROM is write-protected bit 6 WRTB: Boot Block Write Protection bit 1 = Boot block (000000-0007FFh) is not write-protected 0 = Boot block (000000-0007FFh) is write-protected bit 5 WRTC: Configuration Register Write Protection bit(1) 1 = Configuration registers (300000-3000FFh) are not write-protected 0 = Configuration registers (300000-3000FFh) are write-protected bit 4-0 Unimplemented: Read as ‘0’ Note 1: This bit is read-only in normal execution mode; it can be written only in Program mode. © 2009 Microchip Technology Inc. DS39632E-page 301 PIC18F2455/2550/4455/4550 REGISTER 25-11: CONFIG7L: CONFIGURATION REGISTER 7 LOW (BYTE ADDRESS 30000Ch) U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1 — — — — EBTR3(1) EBTR2 EBTR1 EBTR0 bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-4 Unimplemented: Read as ‘0’ bit 3 EBTR3: Table Read Protection bit(1) 1 = Block 3 (006000-007FFFh) not protected from table reads executed in other blocks 0 = Block 3 (006000-007FFFh) protected from table reads executed in other blocks bit 2 EBTR2: Table Read Protection bit 1 = Block 2 (004000-005FFFh) not protected from table reads executed in other blocks 0 = Block 2 (004000-005FFFh) protected from table reads executed in other blocks bit 1 EBTR1: Table Read Protection bit 1 = Block 1 (002000-003FFFh) is not protected from table reads executed in other blocks 0 = Block 1 (002000-003FFFh) is protected from table reads executed in other blocks bit 0 EBTR0: Table Read Protection bit 1 = Block 0 (000800-001FFFh) is not protected from table reads executed in other blocks 0 = Block 0 (000800-001FFFh) is protected from table reads executed in other blocks Note 1: Unimplemented in PIC18FX455 devices; maintain this bit set. REGISTER 25-12: CONFIG7H: CONFIGURATION REGISTER 7 HIGH (BYTE ADDRESS 30000Dh) U-0 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0 — EBTRB — — — — — — bit 7 bit 0 Legend: R = Readable bit C = Clearable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7 Unimplemented: Read as ‘0’ bit 6 EBTRB: Boot Block Table Read Protection bit 1 = Boot block (000000-0007FFh) is not protected from table reads executed in other blocks 0 = Boot block (000000-0007FFh) is protected from table reads executed in other blocks bit 5-0 Unimplemented: Read as ‘0’ PIC18F2455/2550/4455/4550 DS39632E-page 302 © 2009 Microchip Technology Inc. REGISTER 25-13: DEVID1: DEVICE ID REGISTER 1 FOR PIC18F2455/2550/4455/4550 DEVICES R R R R R R R R DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0 bit 7 bit 0 Legend: R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-5 DEV2:DEV0: Device ID bits For a complete listing, see Register 25-14. bit 4-0 REV4:REV0: Revision ID bits These bits are used to indicate the device revision. REGISTER 25-14: DEVID2: DEVICE ID REGISTER 2 FOR PIC18F2455/2550/4455/4550 DEVICES R R R R R R R R DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3 bit 7 bit 0 Legend: R = Read-only bit P = Programmable bit U = Unimplemented bit, read as ‘0’ -n = Value when device is unprogrammed u = Unchanged from programmed state bit 7-0 DEV10:DEV3: Device ID bits DEV10:DEV3 (DEVID2<7:0>) DEV2:DEV0 (DEVID1<7:5>) Device 0001 0010 011 PIC18F2455 0010 1010 011 PIC18F2458 0001 0010 010 PIC18F2550 0010 1010 010 PIC18F2553 0001 0010 001 PIC18F4455 0010 1010 001 PIC18F4458 0001 0010 000 PIC18F4550 0010 1010 000 PIC18F4553 © 2009 Microchip Technology Inc. DS39632E-page 303 PIC18F2455/2550/4455/4550 25.2 Watchdog Timer (WDT) For PIC18F2455/2550/4455/4550 devices, the WDT is driven by the INTRC source. When the WDT is enabled, the clock source is also enabled. The nominal WDT period is 4 ms and has the same stability as the INTRC oscillator. The 4 ms period of the WDT is multiplied by a 16-bit postscaler. Any output of the WDT postscaler is selected by a multiplexer, controlled by bits in Configuration Register 2H. Available periods range from 4 ms to 131.072 seconds (2.18 minutes). The WDT and postscaler are cleared when any of the following events occur: a SLEEP or CLRWDT instruction is executed, the IRCF bits (OSCCON<6:4>) are changed or a clock failure has occurred. . 25.2.1 CONTROL REGISTER Register 25-15 shows the WDTCON register. This is a readable and writable register which contains a control bit that allows software to override the WDT enable Configuration bit, but only if the Configuration bit has disabled the WDT. FIGURE 25-1: WDT BLOCK DIAGRAM Note 1: The CLRWDT and SLEEP instructions clear the WDT and postscaler counts when executed. 2: Changing the setting of the IRCF bits (OSCCON<6:4>) clears the WDT and postscaler counts. 3: When a CLRWDT instruction is executed, the postscaler count will be cleared. INTRC Source WDT Wake-up from Reset WDT WDT Counter Programmable Postscaler 1:1 to 1:32,768 Enable WDT WDTPS<3:0> SWDTEN WDTEN CLRWDT 4 Power-Managed Reset All Device Resets SLEEP INTRC Control ÷128 Change on IRCF bits Modes PIC18F2455/2550/4455/4550 DS39632E-page 304 © 2009 Microchip Technology Inc. TABLE 25-2: SUMMARY OF WATCHDOG TIMER REGISTERS REGISTER 25-15: WDTCON: WATCHDOG TIMER CONTROL REGISTER U-0 U-0 U-0 U-0 U-0 U-0 U-0 R/W-0 — — — — — — — SWDTEN(1) bit 7 bit 0 Legend: R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ -n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown bit 7-1 Unimplemented: Read as ‘0’ bit 0 SWDTEN: Software Controlled Watchdog Timer Enable bit(1) 1 = Watchdog Timer is on 0 = Watchdog Timer is off Note 1: This bit has no effect if the Configuration bit, WDTEN, is enabled. Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Reset Values on page RCON IPEN SBOREN(1) — RI TO PD POR BOR 54 WDTCON — — — — — — — SWDTEN 54 Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Watchdog Timer. Note 1: The SBOREN bit is only available when BOREN<1:0> = 01; otherwise, the bit reads as ‘0’. © 2009 Microchip Technology Inc. DS39632E-page 305 PIC18F2455/2550/4455/4550 25.3 Two-Speed Start-up The Two-Speed Start-up feature helps to minimize the latency period, from oscillator start-up to code execution, by allowing the microcontroller to use the INTRC oscillator as a clock source until the primary clock source is available. It is enabled by setting the IESO Configuration bit. Two-Speed Start-up should be enabled only if the primary oscillator mode is XT, HS, XTPLL or HSPLL (Crystal-Based modes). Other sources do not require an OST start-up delay; for these, Two-Speed Start-up should be disabled. When enabled, Resets and wake-ups from Sleep mode cause the device to configure itself to run from the internal oscillator block as the clock source, following the time-out of the Power-up Timer after a Power-on Reset is enabled. This allows almost immediate code execution while the primary oscillator starts and the OST is running. Once the OST times out, the device automatically switches to PRI_RUN mode. Because the OSCCON register is cleared on Reset events, the INTOSC (or postscaler) clock source is not initially available after a Reset event; the INTRC clock is used directly at its base frequency. To use a higher clock speed on wake-up, the INTOSC or postscaler clock sources can be selected to provide a higher clock speed by setting bits, IRCF2:IRCF0, immediately after Reset. For wake-ups from Sleep, the INTOSC or postscaler clock sources can be selected by setting IRCF2:IRCF0 prior to entering Sleep mode. In all other power-managed modes, Two-Speed Start-up is not used. The device will be clocked by the currently selected clock source until the primary clock source becomes available. The setting of the IESO bit is ignored. 25.3.1 SPECIAL CONSIDERATIONS FOR USING TWO-SPEED START-UP While using the INTRC oscillator in Two-Speed Start-up, the device still obeys the normal command sequences for entering power-managed modes, including serial SLEEP instructions (refer to Section 3.1.4 “Multiple Sleep Commands”). In practice, this means that user code can change the SCS1:SCS0 bit settings or issue SLEEP instructions before the OST times out. This would allow an application to briefly wake-up, perform routine “housekeeping” tasks and return to Sleep before the device starts to operate from the primary oscillator. User code can also check if the primary clock source is currently providing the device clocking by checking the status of the OSTS bit (OSCCON<3>). If the bit is set, the primary oscillator is providing the clock. Otherwise, the internal oscillator block is providing the clock during wake-up from Reset or Sleep mode. FIGURE 25-2: TIMING TRANSITION FOR TWO-SPEED START-UP (INTOSC TO HSPLL) Q1 Q3 Q4 OSC1 Peripheral Program PC PC + 2 INTOSC PLL Clock Q1 PC + 6 Q2 Output Q3 Q4 Q1 CPU Clock PC + 4 Clock Counter Q2 Q2 Q3 Note 1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale. Wake from Interrupt Event TPLL(1) 1 2 n-1 n Clock OSTS bit Set Transition Multiplexer TOST(1) PIC18F2455/2550/4455/4550 DS39632E-page 306 © 2009 Microchip Technology Inc. 25.4 Fail-Safe Clock Monitor The Fail-Safe Clock Monitor (FSCM) allows the microcontroller to continue operation in the event of an external oscillator failure by automatically switching the device clock to the internal oscillator block. The FSCM function is enabled by setting the FCMEN Configuration bit. When FSCM is enabled, the INTRC oscillator runs at all times to monitor clocks to peripherals and provide a backup clock in the event of a clock failure. Clock monitoring (shown in Figure 25-3) is accomplished by creating a sample clock signal, which is the INTRC output divided by 64. This allows ample time between FSCM sample clocks for a peripheral clock edge to occur. The peripheral device clock and the sample clock are presented as inputs to the Clock Monitor latch (CM). The CM is set on the falling edge of the device clock source, but cleared on the rising edge of the sample clock. FIGURE 25-3: FSCM BLOCK DIAGRAM Clock failure is tested for on the falling edge of the sample clock. If a sample clock falling edge occurs while CM is still set, a clock failure has been detected (Figure 25-4). This causes the following: • the FSCM generates an oscillator fail interrupt by setting bit, OSCFIF (PIR2<7>); • the device clock source is switched to the internal oscillator block (OSCCON is not updated to show the current clock source – this is the fail-safe condition); and • the WDT is reset. During switchover, the postscaler frequency from the internal oscillator block may not be sufficiently stable for timing sensitive applications. In these cases, it may be desirable to select another clock configuration and enter an alternate power-managed mode. This can be done to attempt a partial recovery or execute a controlled shutdown. See Section 3.1.4 “Multiple Sleep Commands” and Section 25.3.1 “Special Considerations for Using Two-Speed Start-up” for more details. To use a higher clock speed on wake-up, the INTOSC or postscaler clock sources can be selected to provide a higher clock speed by setting bits IRCF2:IRCF0 immediately after Reset. For wake-ups from Sleep, the INTOSC or postscaler clock sources can be selected by setting IRCF2:IRCF0 prior to entering Sleep mode. The FSCM will detect failures of the primary or secondary clock sources only. If the internal oscillator block fails, no failure would be detected, nor would any action be possible. 25.4.1 FSCM AND THE WATCHDOG TIMER Both the FSCM and the WDT are clocked by the INTRC oscillator. Since the WDT operates with a separate divider and counter, disabling the WDT has no effect on the operation of the INTRC oscillator when the FSCM is enabled. As already noted, the clock source is switched to the INTOSC clock when a clock failure is detected. Depending on the frequency selected by the IRCF2:IRCF0 bits, this may mean a substantial change in the speed of code execution. If the WDT is enabled with a small prescale value, a decrease in clock speed allows a WDT time-out to occur and a subsequent device Reset. For this reason, Fail-Safe Clock Monitor events also reset the WDT and postscaler, allowing it to start timing from when execution speed was changed and decreasing the likelihood of an erroneous time-out. 25.4.2 EXITING FAIL-SAFE OPERATION The fail-safe condition is terminated by either a device Reset or by entering a power-managed mode. On Reset, the controller starts the primary clock source specified in Configuration Register 1H (with any start-up delays that are required for the oscillator mode, such as OST or PLL timer). The INTOSC multiplexer provides the device clock until the primary clock source becomes ready (similar to a Two-Speed Start-up). The clock source is then switched to the primary clock (indicated by the OSTS bit in the OSCCON register becoming set). The Fail-Safe Clock Monitor then resumes monitoring the peripheral clock. The primary clock source may never become ready during start-up. In this case, operation is clocked by the INTOSC multiplexer. The OSCCON register will remain in its Reset state until a power-managed mode is entered. Peripheral INTRC ÷ 64 S C Q (32 μs) 488 Hz (2.048 ms) Clock Monitor Latch (CM) (edge-triggered) Clock Failure Detected Source Clock Q © 2009 Microchip Technology Inc. DS39632E-page 307 PIC18F2455/2550/4455/4550 FIGURE 25-4: FSCM TIMING DIAGRAM 25.4.3 FSCM INTERRUPTS IN POWER-MANAGED MODES By entering a power-managed mode, the clock multiplexer selects the clock source selected by the OSCCON register. Fail-Safe Clock Monitoring of the power-managed clock source resumes in the power-managed mode. If an oscillator failure occurs during power-managed operation, the subsequent events depend on whether or not the oscillator failure interrupt is enabled. If enabled (OSCFIF = 1), code execution will be clocked by the INTOSC multiplexer. An automatic transition back to the failed clock source will not occur. If the interrupt is disabled, subsequent interrupts while in Idle mode will cause the CPU to begin executing instructions while being clocked by the INTOSC source. 25.4.4 POR OR WAKE-UP FROM SLEEP The FSCM is designed to detect oscillator failure at any point after the device has exited Power-on Reset (POR) or low-power Sleep mode. When the primary device clock is either EC or INTRC, monitoring can begin immediately following these events. For oscillator modes involving a crystal or resonator (HS, HSPLL or XT), the situation is somewhat different. Since the oscillator may require a start-up time considerably longer than the FCSM sample clock time, a false clock failure may be detected. To prevent this, the internal oscillator block is automatically configured as the device clock and functions until the primary clock is stable (the OST and PLL timers have timed out). This is identical to Two-Speed Start-up mode. Once the primary clock is stable, the INTRC returns to its role as the FSCM source. As noted in Section 25.3.1 “Special Considerations for Using Two-Speed Start-up”, it is also possible to select another clock configuration and enter an alternate power-managed mode while waiting for the primary clock to become stable. When the new power-managed mode is selected, the primary clock is disabled. OSCFIF CM Output Device Clock Output Sample Clock Failure Detected Oscillator Failure Note: The device clock is normally at a much higher frequency than the sample clock. The relative frequencies in this example have been chosen for clarity. (Q) CM Test CM Test CM Test Note: The same logic that prevents false oscillator failure interrupts on POR or wake from Sleep will also prevent the detection of the oscillator’s failure to start at all following these events. This can be avoided by monitoring the OSTS bit and using a timing routine to determine if the oscillator is taking too long to start. Even so, no oscillator failure interrupt will be flagged. PIC18F2455/2550/4455/4550 DS39632E-page 308 © 2009 Microchip Technology Inc. 25.5 Program Verification and Code Protection The overall structure of the code protection on the PIC18 Flash devices differs significantly from other PIC® devices. The user program memory is divided into five blocks. One of these is a boot block of 2 Kbytes. The remainder of the memory is divided into four blocks on binary boundaries. Each of the five blocks has three code protection bits associated with them. They are: • Code-Protect bit (CPn) • Write-Protect bit (WRTn) • External Block Table Read bit (EBTRn) Figure 25-5 shows the program memory organization for 24 and 32-Kbyte devices and the specific code protection bit associated with each block. The actual locations of the bits are summarized in Table 25-3. FIGURE 25-5: CODE-PROTECTED PROGRAM MEMORY TABLE 25-3: SUMMARY OF CODE PROTECTION REGISTERS File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 300008h CONFIG5L — — — — CP3(1) CP2 CP1 CP0 300009h CONFIG5H CPD CPB — — — — — — 30000Ah CONFIG6L — — — — WRT3(1) WRT2 WRT1 WRT0 30000Bh CONFIG6H WRTD WRTB WRTC — — — — — 30000Ch CONFIG7L — — — — EBTR3(1) EBTR2 EBTR1 EBTR0 30000Dh CONFIG7H — EBTRB — — — — — — Legend: Shaded cells are unimplemented. Note 1: Unimplemented in PIC18FX455 devices; maintain this bit set. MEMORY SIZE/DEVICE Block Code Protection 24 Kbytes 32 Kbytes Address Controlled By: Range Boot Block Boot Block 000000h 0007FFh CPB, WRTB, EBTRB Block 0 Block 0 000800h 001FFFh CP0, WRT0, EBTR0 Block 1 Block 1 002000h 003FFFh CP1, WRT1, EBTR1 Block 2 Block 2 004000h 005FFFh CP2, WRT2, EBTR2 Unimplemented Read ‘0’s Block 3 006000h 007FFFh CP3, WRT3, EBTR3 Unimplemented Read ‘0’s Unimplemented Read ‘0’s 008000h 1FFFFFh (Unimplemented Memory Space) © 2009 Microchip Technology Inc. DS39632E-page 309 PIC18F2455/2550/4455/4550 25.5.1 PROGRAM MEMORY CODE PROTECTION The program memory may be read to or written from any location using the table read and table write instructions. The device ID may be read with table reads. The Configuration registers may be read and written with the table read and table write instructions. In normal execution mode, the CPx bits have no direct effect. CPx bits inhibit external reads and writes. A block of user memory may be protected from table writes if the WRTx Configuration bit is ‘0’. The EBTRx bits control table reads. For a block of user memory with the EBTRx bit set to ‘0’, a table read instruction that executes from within that block is allowed to read. A table read instruction that executes from a location outside of that block is not allowed to read and will result in reading ‘0’s. Figures 25-6 through 25-8 illustrate table write and table read protection. FIGURE 25-6: TABLE WRITE (WRTx) DISALLOWED Note: Code protection bits may only be written to a ‘0’ from a ‘1’ state. It is not possible to write a ‘1’ to a bit in the ‘0’ state. Code protection bits are only set to ‘1’ by a full Chip Erase or Block Erase function. The full Chip Erase and Block Erase functions can only be initiated via ICSP operation or an external programmer. 000000h 0007FFh 000800h 001FFFh 002000h 003FFFh 004000h 005FFFh 006000h 007FFFh WRTB, EBTRB = 11 WRT0, EBTR0 = 01 WRT1, EBTR1 = 11 WRT2, EBTR2 = 11 WRT3, EBTR3 = 11 TBLWT* TBLPTR = 0008FFh PC = 001FFEh PC = 005FFEh TBLWT* Register Values Program Memory Configuration Bit Settings Results: All table writes disabled to Blockn whenever WRTx = 0. PIC18F2455/2550/4455/4550 DS39632E-page 310 © 2009 Microchip Technology Inc. FIGURE 25-7: EXTERNAL BLOCK TABLE READ (EBTRx) DISALLOWED FIGURE 25-8: EXTERNAL BLOCK TABLE READ (EBTRx) ALLOWED WRTB, EBTRB = 11 WRT0, EBTR0 = 10 WRT1, EBTR1 = 11 WRT2, EBTR2 = 11 WRT3, EBTR3 = 11 TBLRD* TBLPTR = 0008FFh PC = 003FFEh Results: All table reads from external blocks to Blockn are disabled whenever EBTRx = 0. TABLAT register returns a value of ‘0’. Register Values Program Memory Configuration Bit Settings 000000h 0007FFh 000800h 001FFFh 002000h 003FFFh 004000h 005FFFh 006000h 007FFFh WRTB, EBTRB = 11 WRT0, EBTR0 = 10 WRT1, EBTR1 = 11 WRT2, EBTR2 = 11 WRT3, EBTR3 = 11 TBLRD* TBLPTR = 0008FFh PC = 001FFEh Register Values Program Memory Configuration Bit Settings Results: Table reads permitted within Blockn, even when EBTRBx = 0. TABLAT register returns the value of the data at the location TBLPTR. 000000h 0007FFh 000800h 001FFFh 002000h 003FFFh 004000h 005FFFh 006000h 007FFFh © 2009 Microchip Technology Inc. DS39632E-page 311 PIC18F2455/2550/4455/4550 25.5.2 DATA EEPROM CODE PROTECTION The entire data EEPROM is protected from external reads and writes by two bits: CPD and WRTD. CPD inhibits external reads and writes of data EEPROM. WRTD inhibits internal and external writes to data EEPROM. The CPU can continue to read and write data EEPROM regardless of the protection bit settings. 25.5.3 CONFIGURATION REGISTER PROTECTION The Configuration registers can be write-protected. The WRTC bit controls protection of the Configuration registers. In normal execution mode, the WRTC bit is readable only. WRTC can only be written via ICSP operation or an external programmer. 25.6 ID Locations Eight memory locations (200000h-200007h) are designated as ID locations, where the user can store checksum or other code identification numbers. These locations are both readable and writable during normal execution through the TBLRD and TBLWT instructions or during program/verify. The ID locations can be read when the device is code-protected. 25.7 In-Circuit Serial Programming PIC18F2455/2550/4455/4550 microcontrollers can be serially programmed while in the end application circuit. This is simply done with two lines for clock and data and three other lines for power, ground and the programming voltage. This allows customers to manufacture boards with unprogrammed devices and then program the microcontroller just before shipping the product. This also allows the most recent firmware or a custom firmware to be programmed. 25.8 In-Circuit Debugger When the DEBUG Configuration bit is programmed to a ‘0’, the In-Circuit Debugger functionality is enabled. This function allows simple debugging functions when used with MPLAB® IDE. When the microcontroller has this feature enabled, some resources are not available for general use. Table 25-4 shows which resources are required by the background debugger. TABLE 25-4: DEBUGGER RESOURCES To use the In-Circuit Debugger function of the microcontroller, the design must implement In-Circuit Serial Programming connections to MCLR/VPP/RE3, VDD, VSS, RB7 and RB6. This will interface to the In-Circuit Debugger module available from Microchip or one of the third party development tool companies. 25.9 Special ICPORT Features (44-Pin TQFP Package Only) Under specific circumstances, the No Connect (NC) pins of devices in 44-pin TQFP packages can provide additional functionality. These features are controlled by device Configuration bits and are available only in this package type and pin count. 25.9.1 DEDICATED ICD/ICSP PORT The 44-pin TQFP devices can use NC pins to provide an alternate port for In-Circuit Debugging (ICD) and In-Circuit Serial Programming (ICSP). These pins are collectively known as the dedicated ICSP/ICD port, since they are not shared with any other function of the device. When implemented, the dedicated port activates three NC pins to provide an alternate device Reset, data and clock ports. None of these ports overlap with standard I/O pins, making the I/O pins available to the user’s application. The dedicated ICSP/ICD port is enabled by setting the ICPRT Configuration bit. The port functions the same way as the legacy ICSP/ICD port on RB6/RB7. Table 25-5 identifies the functionally equivalent pins for ICSP and ICD purposes. TABLE 25-5: EQUIVALENT PINS FOR LEGACY AND DEDICATED ICD/ICSP™ PORTS I/O pins: RB6, RB7 Stack: 2 levels Program Memory: 512 bytes Data Memory: 10 bytes Pin Name Pin Legacy Type Pin Function Port Dedicated Port MCLR/VPP/ RE3 NC/ICRST/ ICVPP P Device Reset and Programming Enable RB6/KBI2/ PGC NC/ICCK/ ICPGC I Serial Clock RB7/KBI3/ PGD NC/ICDT/ ICPGD I/O Serial Data Legend: I = Input, O = Output, P = Power PIC18F2455/2550/4455/4550 DS39632E-page 312 © 2009 Microchip Technology Inc. Even when the dedicated port is enabled, the ICSP functions remain available through the legacy port. When VIHH is seen on the MCLR/VPP/RE3 pin, the state of the ICRST/ICVPP pin is ignored. 25.9.2 28-PIN EMULATION Devices in 44-pin TQFP packages also have the ability to change their configuration under external control for debugging purposes. This allows the device to behave as if it were a 28-pin device. This 28-pin Configuration mode is controlled through a single pin, NC/ICPORTS. Connecting this pin to VSS forces the device to function as a 28-pin device. Features normally associated with the 40/44-pin devices are disabled along with their corresponding control registers and bits. This includes PORTD and PORTE, the SPP and the Enhanced PWM functionality of CCP1. On the other hand, connecting the pin to VDD forces the device to function in its default configuration. The configuration option is only available when background debugging and the dedicated ICD/ICSP port are both enabled (DEBUG Configuration bit is clear and ICPRT Configuration bit is set). When disabled, NC/ICPORTS is a No Connect pin. 25.10 Single-Supply ICSP Programming The LVP Configuration bit enables Single-Supply ICSP Programming (formerly known as Low-Voltage ICSP Programming or LVP). When Single-Supply Programming is enabled, the microcontroller can be programmed without requiring high voltage being applied to the MCLR/VPP/RE3 pin, but the RB5/KBI1/PGM pin is then dedicated to controlling Program mode entry and is not available as a general purpose I/O pin. While programming using Single-Supply Programming, VDD is applied to the MCLR/VPP/RE3 pin as in normal execution mode. To enter Programming mode, VDD is applied to the PGM pin. If Single-Supply ICSP Programming mode will not be used, the LVP bit can be cleared. RB5/KBI1/PGM then becomes available as the digital I/O pin, RB5. The LVP bit may be set or cleared only when using standard high-voltage programming (VIHH applied to the MCLR/VPP/RE3 pin). Once LVP has been disabled, only the standard high-voltage programming is available and must be used to program the device. Memory that is not code-protected can be erased using either a Block Erase, or erased row by row, then written at any specified VDD. If code-protected memory is to be erased, a Block Erase is required. If a Block Erase is to be performed when using Low-Voltage Programming, the device must be supplied with VDD of 4.5V to 5.5V. Note 1: The ICPRT Configuration bit can only be programmed through the default ICSP port (MCLR/RB6/RB7). 2: The ICPRT Configuration bit must be maintained clear for all 28-pin and 40-pin devices; otherwise, unexpected operation may occur. Note 1: High-Voltage Programming is always available, regardless of the state of the LVP bit, by applying VIHH to the MCLR pin. 2: While in Low-Voltage ICSP Programming mode, the RB5 pin can no longer be used as a general purpose I/O pin and should be held low during normal operation. 3: When using Low-Voltage ICSP Programming (LVP) and the pull-ups on PORTB are enabled, bit 5 in the TRISB register must be cleared to disable the pull-up on RB5 and ensure the proper operation of the device. 4: If the device Master Clear is disabled, verify that either of the following is done to ensure proper entry into ICSP mode: a) disable Low-Voltage Programming (CONFIG4L<2> = 0); or b) make certain that RB5/KBI1/PGM is held low during entry into ICSP. © 2009 Microchip Technology Inc. DS39632E-page 313 PIC18F2455/2550/4455/4550 26.0 INSTRUCTION SET SUMMARY PIC18F2455/2550/4455/4550 devices incorporate the standard set of 75 PIC18 core instructions, as well as an extended set of eight new instructions for the optimization of code that is recursive or that utilizes a software stack. The extended set is discussed later in this section. 26.1 Standard Instruction Set The standard PIC18 instruction set adds many enhancements to the previous PIC MCU instruction sets, while maintaining an easy migration from these PIC MCU instruction sets. Most instructions are a single program memory word (16 bits) but there are four instructions that require two program memory locations. Each single-word instruction is a 16-bit word divided into an opcode, which specifies the instruction type and one or more operands, which further specify the operation of the instruction. The instruction set is highly orthogonal and is grouped into four basic categories: • Byte-oriented operations • Bit-oriented operations • Literal operations • Control operations The PIC18 instruction set summary in Table 26-2 lists byte-oriented, bit-oriented, literal and control operations. Table 26-1 shows the opcode field descriptions. Most byte-oriented instructions have three operands: 1. The file register (specified by ‘f’) 2. The destination of the result (specified by ‘d’) 3. The accessed memory (specified by ‘a’) The file register designator ‘f’ specifies which file register is to be used by the instruction. The destination designator ‘d’ specifies where the result of the operation is to be placed. If ‘d’ is zero, the result is placed in the WREG register. If ‘d’ is one, the result is placed in the file register specified in the instruction. All bit-oriented instructions have three operands: 1. The file register (specified by ‘f’) 2. The bit in the file register (specified by ‘b’) 3. The accessed memory (specified by ‘a’) The bit field designator ‘b’ selects the number of the bit affected by the operation, while the file register designator ‘f’ represents the number of the file in which the bit is located. The literal instructions may use some of the following operands: • A literal value to be loaded into a file register (specified by ‘k’) • The desired FSR register to load the literal value into (specified by ‘f’) • No operand required (specified by ‘—’) The control instructions may use some of the following operands: • A program memory address (specified by ‘n’) • The mode of the CALL or RETURN instructions (specified by ‘s’) • The mode of the table read and table write instructions (specified by ‘m’) • No operand required (specified by ‘—’) All instructions are a single word, except for four double-word instructions. These instructions were made double-word to contain the required information in 32 bits. In the second word, the 4 MSbs are ‘1’s. If this second word is executed as an instruction (by itself), it will execute as a NOP. All single-word instructions are executed in a single instruction cycle, unless a conditional test is true or the program counter is changed as a result of the instruction. In these cases, the execution takes two instruction cycles with the additional instruction cycle(s) executed as a NOP. The double-word instructions execute in two instruction cycles. One instruction cycle consists of four oscillator periods. Thus, for an oscillator frequency of 4 MHz, the normal instruction execution time is 1 μs. If a conditional test is true, or the program counter is changed as a result of an instruction, the instruction execution time is 2 μs. Two-word branch instructions (if true) would take 3 μs. Figure 26-1 shows the general formats that the instructions can have. All examples use the convention ‘nnh’ to represent a hexadecimal number. The instruction set summary, shown in Table 26-2, lists the standard instructions recognized by the Microchip MPASMTM Assembler. Section 26.1.1 “Standard Instruction Set” provides a description of each instruction. PIC18F2455/2550/4455/4550 DS39632E-page 314 © 2009 Microchip Technology Inc. TABLE 26-1: OPCODE FIELD DESCRIPTIONS Field Description a RAM access bit a = 0: RAM location in Access RAM (BSR register is ignored) a = 1: RAM bank is specified by BSR register bbb Bit address within an 8-bit file register (0 to 7). BSR Bank Select Register. Used to select the current RAM bank. C, DC, Z, OV, N ALU Status bits: Carry, Digit Carry, Zero, Overflow, Negative. d Destination select bit d = 0: store result in WREG d = 1: store result in file register f dest Destination: either the WREG register or the specified register file location. f 8-bit register file address (00h to FFh) or 2-bit FSR designator (0h to 3h). fs 12-bit register file address (000h to FFFh). This is the source address. fd 12-bit register file address (000h to FFFh). This is the destination address. GIE Global Interrupt Enable bit. k Literal field, constant data or label (may be either an 8-bit, 12-bit or a 20-bit value). label Label name. mm The mode of the TBLPTR register for the table read and table write instructions. Only used with table read and table write instructions: * No change to register (such as TBLPTR with table reads and writes) *+ Post-Increment register (such as TBLPTR with table reads and writes) *- Post-Decrement register (such as TBLPTR with table reads and writes) +* Pre-Increment register (such as TBLPTR with table reads and writes) n The relative address (2’s complement number) for relative branch instructions or the direct address for Call/Branch and Return instructions. PC Program Counter. PCL Program Counter Low Byte. PCH Program Counter High Byte. PCLATH Program Counter High Byte Latch. PCLATU Program Counter Upper Byte Latch. PD Power-Down bit. PRODH Product of Multiply High Byte. PRODL Product of Multiply Low Byte. s Fast Call/Return mode select bit s = 0: do not update into/from shadow registers s = 1: certain registers loaded into/from shadow registers (Fast mode) TBLPTR 21-bit Table Pointer (points to a program memory location). TABLAT 8-bit Table Latch. TO Time-out bit. TOS Top-of-Stack. u Unused or unchanged. WDT Watchdog Timer. WREG Working register (accumulator). x Don’t care (‘0’ or ‘1’). The assembler will generate code with x = 0. It is the recommended form of use for compatibility with all Microchip software tools. zs 7-bit offset value for indirect addressing of register files (source). zd 7-bit offset value for indirect addressing of register files (destination). { } Optional argument. [text] Indicates an indexed address. (text) The contents of text. [expr] Specifies bit n of the register indicated by the pointer expr. → Assigned to. < > Register bit field. ∈ In the set of. italics User-defined term (font is Courier New). © 2009 Microchip Technology Inc. DS39632E-page 315 PIC18F2455/2550/4455/4550 FIGURE 26-1: GENERAL FORMAT FOR INSTRUCTIONS Byte-oriented file register operations 15 10 9 8 7 0 d = 0 for result destination to be WREG register OPCODE d a f (FILE #) d = 1 for result destination to be file register (f) a = 0 to force Access Bank Bit-oriented file register operations 15 12 11 9 8 7 0 OPCODE b (BIT #) a f (FILE #) b = 3-bit position of bit in file register (f) Literal operations 15 8 7 0 OPCODE k (literal) k = 8-bit immediate value Byte to Byte move operations (2-word) 15 12 11 0 OPCODE f (Source FILE #) CALL, GOTO and Branch operations 15 8 7 0 OPCODE n<7:0> (literal) n = 20-bit immediate value a = 1 for BSR to select bank f = 8-bit file register address a = 0 to force Access Bank a = 1 for BSR to select bank f = 8-bit file register address 15 12 11 0 1111 n<19:8> (literal) 15 12 11 0 1111 f (Destination FILE #) f = 12-bit file register address Control operations Example Instruction ADDWF MYREG, W, B MOVFF MYREG1, MYREG2 BSF MYREG, bit, B MOVLW 7Fh GOTO Label 15 8 7 0 OPCODE n<7:0> (literal) 15 12 11 0 1111 n<19:8> (literal) CALL MYFUNC 15 11 10 0 OPCODE n<10:0> (literal) S = Fast bit BRA MYFUNC 15 8 7 0 OPCODE n<7:0> (literal) BC MYFUNC S PIC18F2455/2550/4455/4550 DS39632E-page 316 © 2009 Microchip Technology Inc. TABLE 26-2: PIC18FXXXX INSTRUCTION SET Mnemonic, Operands Description Cycles 16-Bit Instruction Word Status Affected Notes MSb LSb BYTE-ORIENTED OPERATIONS ADDWF ADDWFC ANDWF CLRF COMF CPFSEQ CPFSGT CPFSLT DECF DECFSZ DCFSNZ INCF INCFSZ INFSNZ IORWF MOVF MOVFF MOVWF MULWF NEGF RLCF RLNCF RRCF RRNCF SETF SUBFWB SUBWF SUBWFB SWAPF TSTFSZ XORWF f, d, a f, d, a f, d, a f, a f, d, a f, a f, a f, a f, d, a f, d, a f, d, a f, d, a f, d, a f, d, a f, d, a f, d, a fs, fd f, a f, a f, a f, d, a f, d, a f, d, a f, d, a f, a f, d, a f, d, a f, d, a f, d, a f, a f, d, a Add WREG and f Add WREG and Carry bit to f AND WREG with f Clear f Complement f Compare f with WREG, Skip = Compare f with WREG, Skip > Compare f with WREG, Skip < Decrement f Decrement f, Skip if 0 Decrement f, Skip if Not 0 Increment f Increment f, Skip if 0 Increment f, Skip if Not 0 Inclusive OR WREG with f Move f Move fs (source) to 1st word fd (destination) 2nd word Move WREG to f Multiply WREG with f Negate f Rotate Left f through Carry Rotate Left f (No Carry) Rotate Right f through Carry Rotate Right f (No Carry) Set f Subtract f from WREG with Borrow Subtract WREG from f Subtract WREG from f with Borrow Swap Nibbles in f Test f, Skip if 0 Exclusive OR WREG with f 11111 1 (2 or 3) 1 (2 or 3) 1 (2 or 3) 1 1 (2 or 3) 1 (2 or 3) 1 1 (2 or 3) 1 (2 or 3) 112 111111111 11 1 1 (2 or 3) 1 0010 0010 0001 0110 0001 0110 0110 0110 0000 0010 0100 0010 0011 0100 0001 0101 1100 1111 0110 0000 0110 0011 0100 0011 0100 0110 0101 0101 0101 0011 0110 0001 01da 00da 01da 101a 11da 001a 010a 000a 01da 11da 11da 10da 11da 10da 00da 00da ffff ffff 111a 001a 110a 01da 01da 00da 00da 100a 01da 11da 10da 10da 011a 10da ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff C, DC, Z, OV, N C, DC, Z, OV, N Z, N Z Z, N None None None C, DC, Z, OV, N None None C, DC, Z, OV, N None None Z, N Z, N None None None C, DC, Z, OV, N C, Z, N Z, N C, Z, N Z, N None C, DC, Z, OV, N C, DC, Z, OV, N C, DC, Z, OV, N None None Z, N 1, 2 1, 2 1,2 2 1, 2 44 1, 2 1, 2, 3, 4 1, 2, 3, 4 1, 2 1, 2, 3, 4 4 1, 2 1, 2 1 1, 2 1, 2 1, 2 1, 2 4 1, 2 Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as an input and is driven low by an external device, the data will be written back with a ‘0’. 2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if assigned. 3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is executed as a NOP. 4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory locations have a valid instruction. © 2009 Microchip Technology Inc. DS39632E-page 317 PIC18F2455/2550/4455/4550 BIT-ORIENTED OPERATIONS BCF BSF BTFSC BTFSS BTG f, b, a f, b, a f, b, a f, b, a f, d, a Bit Clear f Bit Set f Bit Test f, Skip if Clear Bit Test f, Skip if Set Bit Toggle f 11 1 (2 or 3) 1 (2 or 3) 1 1001 1000 1011 1010 0111 bbba bbba bbba bbba bbba ffff ffff ffff ffff ffff ffff ffff ffff ffff ffff None None None None None 1, 2 1, 2 3, 4 3, 4 1, 2 CONTROL OPERATIONS BC BN BNC BNN BNOV BNZ BOV BRA BZ CALL CLRWDT DAW GOTO NOP NOP POP PUSH RCALL RESET RETFIE RETLW RETURN SLEEP nnnnnnnnn n, s ——n ————n s ks — Branch if Carry Branch if Negative Branch if Not Carry Branch if Not Negative Branch if Not Overflow Branch if Not Zero Branch if Overflow Branch Unconditionally Branch if Zero Call Subroutine 1st word 2nd word Clear Watchdog Timer Decimal Adjust WREG Go to Address 1st word 2nd word No Operation No Operation Pop Top of Return Stack (TOS) Push Top of Return Stack (TOS) Relative Call Software Device Reset Return from Interrupt Enable Return with Literal in WREG Return from Subroutine Go into Standby mode 1 (2) 1 (2) 1 (2) 1 (2) 1 (2) 1 (2) 1 (2) 2 1 (2) 2 112 1111212 221 1110 1110 1110 1110 1110 1110 1110 1101 1110 1110 1111 0000 0000 1110 1111 0000 1111 0000 0000 1101 0000 0000 0000 0000 0000 0010 0110 0011 0111 0101 0001 0100 0nnn 0000 110s kkkk 0000 0000 1111 kkkk 0000 xxxx 0000 0000 1nnn 0000 0000 1100 0000 0000 nnnn nnnn nnnn nnnn nnnn nnnn nnnn nnnn nnnn kkkk kkkk 0000 0000 kkkk kkkk 0000 xxxx 0000 0000 nnnn 1111 0001 kkkk 0001 0000 nnnn nnnn nnnn nnnn nnnn nnnn nnnn nnnn nnnn kkkk kkkk 0100 0111 kkkk kkkk 0000 xxxx 0110 0101 nnnn 1111 000s kkkk 001s 0011 None None None None None None None None None None TO, PD C None None None None None None All GIE/GIEH, PEIE/GIEL None None TO, PD 4 TABLE 26-2: PIC18FXXXX INSTRUCTION SET (CONTINUED) Mnemonic, Operands Description Cycles 16-Bit Instruction Word Status Affected Notes MSb LSb Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as an input and is driven low by an external device, the data will be written back with a ‘0’. 2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if assigned. 3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is executed as a NOP. 4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory locations have a valid instruction. PIC18F2455/2550/4455/4550 DS39632E-page 318 © 2009 Microchip Technology Inc. LITERAL OPERATIONS ADDLW ANDLW IORLW LFSR MOVLB MOVLW MULLW RETLW SUBLW XORLW kkk f, k kkkkkk Add Literal and WREG AND Literal with WREG Inclusive OR Literal with WREG Move Literal (12-bit) 2nd word to FSR(f) 1st word Move Literal to BSR<3:0> Move Literal to WREG Multiply Literal with WREG Return with Literal in WREG Subtract WREG from Literal Exclusive OR Literal with WREG 1112 111211 0000 0000 0000 1110 1111 0000 0000 0000 0000 0000 0000 1111 1011 1001 1110 0000 0001 1110 1101 1100 1000 1010 kkkk kkkk kkkk 00ff kkkk 0000 kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk kkkk C, DC, Z, OV, N Z, N Z, N None None None None None C, DC, Z, OV, N Z, N DATA MEMORY ↔ PROGRAM MEMORY OPERATIONS TBLRD* TBLRD*+ TBLRD*- TBLRD+* TBLWT* TBLWT*+ TBLWT*- TBLWT+* Table Read Table Read with Post-Increment Table Read with Post-Decrement Table Read with Pre-Increment Table Write Table Write with Post-Increment Table Write with Post-Decrement Table Write with Pre-Increment 2 2 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 1000 1001 1010 1011 1100 1101 1110 1111 None None None None None None None None TABLE 26-2: PIC18FXXXX INSTRUCTION SET (CONTINUED) Mnemonic, Operands Description Cycles 16-Bit Instruction Word Status Affected Notes MSb LSb Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as an input and is driven low by an external device, the data will be written back with a ‘0’. 2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if assigned. 3: If the Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is executed as a NOP. 4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory locations have a valid instruction. © 2009 Microchip Technology Inc. DS39632E-page 319 PIC18F2455/2550/4455/4550 26.1.1 STANDARD INSTRUCTION SET ADDLW ADD Literal to W Syntax: ADDLW k Operands: 0 ≤ k ≤ 255 Operation: (W) + k → W Status Affected: N, OV, C, DC, Z Encoding: 0000 1111 kkkk kkkk Description: The contents of W are added to the 8-bit literal ‘k’ and the result is placed in W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example: ADDLW 15h Before Instruction W = 10h After Instruction W = 25h ADDWF ADD W to f Syntax: ADDWF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) + (f) → dest Status Affected: N, OV, C, DC, Z Encoding: 0010 01da ffff ffff Description: Add W to register ‘f’. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: ADDWF REG, 0, 0 Before Instruction W = 17h REG = 0C2h After Instruction W = 0D9h REG = 0C2h Note: All PIC18 instructions may take an optional label argument, preceding the instruction mnemonic, for use in symbolic addressing. If a label is used, the instruction format then becomes: {label} instruction argument(s). PIC18F2455/2550/4455/4550 DS39632E-page 320 © 2009 Microchip Technology Inc. ADDWFC ADD W and Carry bit to f Syntax: ADDWFC f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) + (f) + (C) → dest Status Affected: N, OV, C, DC, Z Encoding: 0010 00da ffff ffff Description: Add W, the Carry flag and data memory location ‘f’. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed in data memory location ‘f’. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: ADDWFC REG, 0, 1 Before Instruction Carry bit = 1 REG = 02h W = 4Dh After Instruction Carry bit = 0 REG = 02h W = 50h ANDLW AND Literal with W Syntax: ANDLW k Operands: 0 ≤ k ≤ 255 Operation: (W) .AND. k → W Status Affected: N, Z Encoding: 0000 1011 kkkk kkkk Description: The contents of W are ANDed with the 8-bit literal ‘k’. The result is placed in W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example: ANDLW 05Fh Before Instruction W = A3h After Instruction W = 03h © 2009 Microchip Technology Inc. DS39632E-page 321 PIC18F2455/2550/4455/4550 ANDWF AND W with f Syntax: ANDWF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) .AND. (f) → dest Status Affected: N, Z Encoding: 0001 01da ffff ffff Description: The contents of W are ANDed with register ‘f’. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: ANDWF REG, 0, 0 Before Instruction W = 17h REG = C2h After Instruction W = 02h REG = C2h BC Branch if Carry Syntax: BC n Operands: -128 ≤ n ≤ 127 Operation: if Carry bit is ‘1’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0010 nnnn nnnn Description: If the Carry bit is ‘1’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BC 5 Before Instruction PC = address (HERE) After Instruction If Carry = 1; PC = address (HERE + 12) If Carry = 0; PC = address (HERE + 2) PIC18F2455/2550/4455/4550 DS39632E-page 322 © 2009 Microchip Technology Inc. BCF Bit Clear f Syntax: BCF f, b {,a} Operands: 0 ≤ f ≤ 255 0 ≤ b ≤ 7 a ∈ [0,1] Operation: 0 → f Status Affected: None Encoding: 1001 bbba ffff ffff Description: Bit ‘b’ in register ‘f’ is cleared. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: BCF FLAG_REG, 7, 0 Before Instruction FLAG_REG = C7h After Instruction FLAG_REG = 47h BN Branch if Negative Syntax: BN n Operands: -128 ≤ n ≤ 127 Operation: if Negative bit is ‘1’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0110 nnnn nnnn Description: If the Negative bit is ‘1’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BN Jump Before Instruction PC = address (HERE) After Instruction If Negative = 1; PC = address (Jump) If Negative = 0; PC = address (HERE + 2) © 2009 Microchip Technology Inc. DS39632E-page 323 PIC18F2455/2550/4455/4550 BNC Branch if Not Carry Syntax: BNC n Operands: -128 ≤ n ≤ 127 Operation: if Carry bit is ‘0’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0011 nnnn nnnn Description: If the Carry bit is ‘0’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BNC Jump Before Instruction PC = address (HERE) After Instruction If Carry = 0; PC = address (Jump) If Carry = 1; PC = address (HERE + 2) BNN Branch if Not Negative Syntax: BNN n Operands: -128 ≤ n ≤ 127 Operation: if Negative bit is ‘0’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0111 nnnn nnnn Description: If the Negative bit is ‘0’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BNN Jump Before Instruction PC = address (HERE) After Instruction If Negative = 0; PC = address (Jump) If Negative = 1; PC = address (HERE + 2) PIC18F2455/2550/4455/4550 DS39632E-page 324 © 2009 Microchip Technology Inc. BNOV Branch if Not Overflow Syntax: BNOV n Operands: -128 ≤ n ≤ 127 Operation: if Overflow bit is ‘0’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0101 nnnn nnnn Description: If the Overflow bit is ‘0’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BNOV Jump Before Instruction PC = address (HERE) After Instruction If Overflow = 0; PC = address (Jump) If Overflow = 1; PC = address (HERE + 2) BNZ Branch if Not Zero Syntax: BNZ n Operands: -128 ≤ n ≤ 127 Operation: if Zero bit is ‘0’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0001 nnnn nnnn Description: If the Zero bit is ‘0’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BNZ Jump Before Instruction PC = address (HERE) After Instruction If Zero = 0; PC = address (Jump) If Zero = 1; PC = address (HERE + 2) © 2009 Microchip Technology Inc. DS39632E-page 325 PIC18F2455/2550/4455/4550 BRA Unconditional Branch Syntax: BRA n Operands: -1024 ≤ n ≤ 1023 Operation: (PC) + 2 + 2n → PC Status Affected: None Encoding: 1101 0nnn nnnn nnnn Description: Add the 2’s complement number ‘2n’ to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is a two-cycle instruction. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation Example: HERE BRA Jump Before Instruction PC = address (HERE) After Instruction PC = address (Jump) BSF Bit Set f Syntax: BSF f, b {,a} Operands: 0 ≤ f ≤ 255 0 ≤ b ≤ 7 a ∈ [0,1] Operation: 1 → f Status Affected: None Encoding: 1000 bbba ffff ffff Description: Bit ‘b’ in register ‘f’ is set. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: BSF FLAG_REG, 7, 1 Before Instruction FLAG_REG = 0Ah After Instruction FLAG_REG = 8Ah PIC18F2455/2550/4455/4550 DS39632E-page 326 © 2009 Microchip Technology Inc. BTFSC Bit Test File, Skip if Clear Syntax: BTFSC f, b {,a} Operands: 0 ≤ f ≤ 255 0 ≤ b ≤ 7 a ∈ [0,1] Operation: skip if (f) = 0 Status Affected: None Encoding: 1011 bbba ffff ffff Description: If bit ‘b’ in register ‘f’ is ‘0’, then the next instruction is skipped. If bit ‘b’ is ‘0’, then the next instruction fetched during the current instruction execution is discarded and a NOP is executed instead, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE FALSE TRUE BTFSC : : FLAG, 1, 0 Before Instruction PC = address (HERE) After Instruction If FLAG<1> = 0; PC = address (TRUE) If FLAG<1> = 1; PC = address (FALSE) BTFSS Bit Test File, Skip if Set Syntax: BTFSS f, b {,a} Operands: 0 ≤ f ≤ 255 0 ≤ b < 7 a ∈ [0,1] Operation: skip if (f) = 1 Status Affected: None Encoding: 1010 bbba ffff ffff Description: If bit ‘b’ in register ‘f’ is ‘1’, then the next instruction is skipped. If bit ‘b’ is ‘1’, then the next instruction fetched during the current instruction execution is discarded and a NOP is executed instead, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE FALSE TRUE BTFSS : : FLAG, 1, 0 Before Instruction PC = address (HERE) After Instruction If FLAG<1> = 0; PC = address (FALSE) If FLAG<1> = 1; PC = address (TRUE) © 2009 Microchip Technology Inc. DS39632E-page 327 PIC18F2455/2550/4455/4550 BTG Bit Toggle f Syntax: BTG f, b {,a} Operands: 0 ≤ f ≤ 255 0 ≤ b < 7 a ∈ [0,1] Operation: (f) → f Status Affected: None Encoding: 0111 bbba ffff ffff Description: Bit ‘b’ in data memory location ‘f’ is inverted. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: BTG PORTC, 4, 0 Before Instruction: PORTC = 0111 0101 [75h] After Instruction: PORTC = 0110 0101 [65h] BOV Branch if Overflow Syntax: BOV n Operands: -128 ≤ n ≤ 127 Operation: if Overflow bit is ‘1’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0100 nnnn nnnn Description: If the Overflow bit is ‘1’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BOV Jump Before Instruction PC = address (HERE) After Instruction If Overflow = 1; PC = address (Jump) If Overflow = 0; PC = address (HERE + 2) PIC18F2455/2550/4455/4550 DS39632E-page 328 © 2009 Microchip Technology Inc. BZ Branch if Zero Syntax: BZ n Operands: -128 ≤ n ≤ 127 Operation: if Zero bit is ‘1’, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1110 0000 nnnn nnnn Description: If the Zero bit is ‘1’, then the program will branch. The 2’s complement number ‘2n’ is added to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is then a two-cycle instruction. Words: 1 Cycles: 1(2) Q Cycle Activity: If Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data Write to PC No operation No operation No operation No operation If No Jump: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Process Data No operation Example: HERE BZ Jump Before Instruction PC = address (HERE) After Instruction If Zero = 1; PC = address (Jump) If Zero = 0; PC = address (HERE + 2) CALL Subroutine Call Syntax: CALL k {,s} Operands: 0 ≤ k ≤ 1048575 s ∈ [0,1] Operation: (PC) + 4 → TOS, k → PC<20:1>; if s = 1, (W) → WS, (STATUS) → STATUSS, (BSR) → BSRS Status Affected: None Encoding: 1st word (k<7:0>) 2nd word(k<19:8>) 1110 1111 110s k19kkk k7kkk kkkk kkkk0 kkkk8 Description: Subroutine call of entire 2-Mbyte memory range. First, return address (PC + 4) is pushed onto the return stack. If ‘s’ = 1, the W, STATUS and BSR registers are also pushed into their respective shadow registers, WS, STATUSS and BSRS. If ‘s’ = 0, no update occurs (default). Then, the 20-bit value ‘k’ is loaded into PC<20:1>. CALL is a two-cycle instruction. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’<7:0>, Push PC to stack Read literal ‘k’<19:8>, Write to PC No operation No operation No operation No operation Example: HERE CALL THERE,1 Before Instruction PC = address (HERE) After Instruction PC = address (THERE) TOS = address (HERE + 4) WS = W BSRS = BSR STATUSS = STATUS © 2009 Microchip Technology Inc. DS39632E-page 329 PIC18F2455/2550/4455/4550 CLRF Clear f Syntax: CLRF f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: 000h → f, 1 → Z Status Affected: Z Encoding: 0110 101a ffff ffff Description: Clears the contents of the specified register. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: CLRF FLAG_REG,1 Before Instruction FLAG_REG = 5Ah After Instruction FLAG_REG = 00h CLRWDT Clear Watchdog Timer Syntax: CLRWDT Operands: None Operation: 000h → WDT, 000h → WDT postscaler, 1 → TO, 1 → PD Status Affected: TO, PD Encoding: 0000 0000 0000 0100 Description: CLRWDT instruction resets the Watchdog Timer. It also resets the postscaler of the WDT. Status bits, TO and PD, are set. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation Process Data No operation Example: CLRWDT Before Instruction WDT Counter = ? After Instruction WDT Counter = 00h WDT Postscaler = 0 TO = 1 PD = 1 PIC18F2455/2550/4455/4550 DS39632E-page 330 © 2009 Microchip Technology Inc. COMF Complement f Syntax: COMF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) → dest Status Affected: N, Z Encoding: 0001 11da ffff ffff Description: The contents of register ‘f’ are complemented. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: COMF REG, 0, 0 Before Instruction REG = 13h After Instruction REG = 13h W = ECh CPFSEQ Compare f with W, Skip if f = W Syntax: CPFSEQ f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (f) – (W), skip if (f) = (W) (unsigned comparison) Status Affected: None Encoding: 0110 001a ffff ffff Description: Compares the contents of data memory location ‘f’ to the contents of W by performing an unsigned subtraction. If ‘f’ = W, then the fetched instruction is discarded and a NOP is executed instead, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE CPFSEQ REG, 0 NEQUAL : EQUAL : Before Instruction PC Address = HERE W = ? REG = ? After Instruction If REG = W; PC = Address (EQUAL) If REG ≠ W; PC = Address (NEQUAL) © 2009 Microchip Technology Inc. DS39632E-page 331 PIC18F2455/2550/4455/4550 CPFSGT Compare f with W, Skip if f > W Syntax: CPFSGT f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (f) – (W), skip if (f) > (W) (unsigned comparison) Status Affected: None Encoding: 0110 010a ffff ffff Description: Compares the contents of data memory location ‘f’ to the contents of the W by performing an unsigned subtraction. If the contents of ‘f’ are greater than the contents of WREG, then the fetched instruction is discarded and a NOP is executed instead, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE CPFSGT REG, 0 NGREATER : GREATER : Before Instruction PC = Address (HERE) W = ? After Instruction If REG > W; PC = Address (GREATER) If REG ≤ W; PC = Address (NGREATER) CPFSLT Compare f with W, Skip if f < W Syntax: CPFSLT f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (f) – (W), skip if (f) < (W) (unsigned comparison) Status Affected: None Encoding: 0110 000a ffff ffff Description: Compares the contents of data memory location ‘f’ to the contents of W by performing an unsigned subtraction. If the contents of ‘f’ are less than the contents of W, then the fetched instruction is discarded and a NOP is executed instead, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE CPFSLT REG, 1 NLESS : LESS : Before Instruction PC = Address (HERE) W = ? After Instruction If REG < W; PC = Address (LESS) If REG ≥ W; PC = Address (NLESS) PIC18F2455/2550/4455/4550 DS39632E-page 332 © 2009 Microchip Technology Inc. DAW Decimal Adjust W Register Syntax: DAW Operands: None Operation: If [W<3:0> > 9] or [DC = 1] then, (W<3:0>) + 6 → W<3:0>; else, (W<3:0>) → W<3:0>; If [W<7:4> + DC > 9] or [C = 1] then, (W<7:4>) + 6 + DC → W<7:4>; else, (W<7:4>) + DC → W<7:4> Status Affected: C Encoding: 0000 0000 0000 0111 Description: DAW adjusts the eight-bit value in W, resulting from the earlier addition of two variables (each in packed BCD format) and produces a correct packed BCD result. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register W Process Data Write W Example 1: DAW Before Instruction W = A5h C = 0 DC = 0 After Instruction W = 05h C = 1 DC = 0 Example 2: Before Instruction W = CEh C = 0 DC = 0 After Instruction W = 34h C = 1 DC = 0 DECF Decrement f Syntax: DECF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) – 1 → dest Status Affected: C, DC, N, OV, Z Encoding: 0000 01da ffff ffff Description: Decrement register ‘f’. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: DECF CNT, 1, 0 Before Instruction CNT = 01h Z = 0 After Instruction CNT = 00h Z = 1 © 2009 Microchip Technology Inc. DS39632E-page 333 PIC18F2455/2550/4455/4550 DECFSZ Decrement f, Skip if 0 Syntax: DECFSZ f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) – 1 → dest, skip if result = 0 Status Affected: None Encoding: 0010 11da ffff ffff Description: The contents of register ‘f’ are decremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If the result is ‘0’, the next instruction, which is already fetched, is discarded and a NOP is executed instead, making it a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE DECFSZ CNT, 1, 1 GOTO LOOP CONTINUE Before Instruction PC = Address (HERE) After Instruction CNT = CNT – 1 If CNT = 0; PC = Address (CONTINUE) If CNT ≠ 0; PC = Address (HERE + 2) DCFSNZ Decrement f, Skip if Not 0 Syntax: DCFSNZ f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) – 1 → dest, skip if result ≠ 0 Status Affected: None Encoding: 0100 11da ffff ffff Description: The contents of register ‘f’ are decremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If the result is not ‘0’, the next instruction, which is already fetched, is discarded and a NOP is executed instead, making it a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE DCFSNZ TEMP, 1, 0 ZERO : NZERO : Before Instruction TEMP = ? After Instruction TEMP = TEMP – 1, If TEMP = 0; PC = Address (ZERO) If TEMP ≠ 0; PC = Address (NZERO) PIC18F2455/2550/4455/4550 DS39632E-page 334 © 2009 Microchip Technology Inc. GOTO Unconditional Branch Syntax: GOTO k Operands: 0 ≤ k ≤ 1048575 Operation: k → PC<20:1> Status Affected: None Encoding: 1st word (k<7:0>) 2nd word(k<19:8>) 1110 1111 1111 k19kkk k7kkk kkkk kkkk0 kkkk8 Description: GOTO allows an unconditional branch anywhere within the entire 2-Mbyte memory range. The 20-bit value ‘k’ is loaded into PC<20:1>. GOTO is always a two-cycle instruction. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’<7:0>, No operation Read literal ‘k’<19:8>, Write to PC No operation No operation No operation No operation Example: GOTO THERE After Instruction PC = Address (THERE) INCF Increment f Syntax: INCF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) + 1 → dest Status Affected: C, DC, N, OV, Z Encoding: 0010 10da ffff ffff Description: The contents of register ‘f’ are incremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: INCF CNT, 1, 0 Before Instruction CNT = FFh Z = 0 C = ? DC = ? After Instruction CNT = 00h Z = 1 C = 1 DC = 1 © 2009 Microchip Technology Inc. DS39632E-page 335 PIC18F2455/2550/4455/4550 INCFSZ Increment f, Skip if 0 Syntax: INCFSZ f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) + 1 → dest, skip if result = 0 Status Affected: None Encoding: 0011 11da ffff ffff Description: The contents of register ‘f’ are incremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’. (default) If the result is ‘0’, the next instruction, which is already fetched, is discarded and a NOP is executed instead, making it a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE INCFSZ CNT, 1, 0 NZERO : ZERO : Before Instruction PC = Address (HERE) After Instruction CNT = CNT + 1 If CNT = 0; PC = Address (ZERO) If CNT ≠ 0; PC = Address (NZERO) INFSNZ Increment f, Skip if Not 0 Syntax: INFSNZ f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) + 1 → dest, skip if result ≠ 0 Status Affected: None Encoding: 0100 10da ffff ffff Description: The contents of register ‘f’ are incremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If the result is not ‘0’, the next instruction, which is already fetched, is discarded and a NOP is executed instead, making it a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE INFSNZ REG, 1, 0 ZERO NZERO Before Instruction PC = Address (HERE) After Instruction REG = REG + 1 If REG ≠ 0; PC = Address (NZERO) If REG = 0; PC = Address (ZERO) PIC18F2455/2550/4455/4550 DS39632E-page 336 © 2009 Microchip Technology Inc. IORLW Inclusive OR Literal with W Syntax: IORLW k Operands: 0 ≤ k ≤ 255 Operation: (W) .OR. k → W Status Affected: N, Z Encoding: 0000 1001 kkkk kkkk Description: The contents of W are ORed with the eight-bit literal ‘k’. The result is placed in W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example: IORLW 35h Before Instruction W = 9Ah After Instruction W = BFh IORWF Inclusive OR W with f Syntax: IORWF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) .OR. (f) → dest Status Affected: N, Z Encoding: 0001 00da ffff ffff Description: Inclusive OR W with register ‘f’. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: IORWF RESULT, 0, 1 Before Instruction RESULT = 13h W = 91h After Instruction RESULT = 13h W = 93h © 2009 Microchip Technology Inc. DS39632E-page 337 PIC18F2455/2550/4455/4550 LFSR Load FSR Syntax: LFSR f, k Operands: 0 ≤ f ≤ 2 0 ≤ k ≤ 4095 Operation: k → FSRf Status Affected: None Encoding: 1110 1111 1110 0000 00ff k7kkk k11kkk kkkk Description: The 12-bit literal ‘k’ is loaded into the File Select Register pointed to by ‘f’. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ MSB Process Data Write literal ‘k’ MSB to FSRfH Decode Read literal ‘k’ LSB Process Data Write literal ‘k’ to FSRfL Example: LFSR 2, 3ABh After Instruction FSR2H = 03h FSR2L = ABh MOVF Move f Syntax: MOVF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: f → dest Status Affected: N, Z Encoding: 0101 00da ffff ffff Description: The contents of register ‘f’ are moved to a destination dependent upon the status of ‘d’. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). Location ‘f’ can be anywhere in the 256-byte bank. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write W Example: MOVF REG, 0, 0 Before Instruction REG = 22h W = FFh After Instruction REG = 22h W = 22h PIC18F2455/2550/4455/4550 DS39632E-page 338 © 2009 Microchip Technology Inc. MOVFF Move f to f Syntax: MOVFF fs,fd Operands: 0 ≤ fs ≤ 4095 0 ≤ fd ≤ 4095 Operation: (fs) → fd Status Affected: None Encoding: 1st word (source) 2nd word (destin.) 1100 1111 ffff ffff ffff ffff ffffs ffffd Description: The contents of source register ‘fs’ are moved to destination register ‘fd’. Location of source ‘fs’ can be anywhere in the 4096-byte data space (000h to FFFh) and location of destination ‘fd’ can also be anywhere from 000h to FFFh. Either source or destination can be W (a useful special situation). MOVFF is particularly useful for transferring a data memory location to a peripheral register (such as the transmit buffer or an I/O port). The MOVFF instruction cannot use the PCL, TOSU, TOSH or TOSL as the destination register. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ (src) Process Data No operation Decode No operation No dummy read No operation Write register ‘f’ (dest) Example: MOVFF REG1, REG2 Before Instruction REG1 = 33h REG2 = 11h After Instruction REG1 = 33h REG2 = 33h MOVLB Move Literal to Low Nibble in BSR Syntax: MOVLW k Operands: 0 ≤ k ≤ 255 Operation: k → BSR Status Affected: None Encoding: 0000 0001 kkkk kkkk Description: The eight-bit literal ‘k’ is loaded into the Bank Select Register (BSR). The value of BSR<7:4> always remains ‘0’ regardless of the value of k7:k4. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write literal ‘k’ to BSR Example: MOVLB 5 Before Instruction BSR Register = 02h After Instruction BSR Register = 05h © 2009 Microchip Technology Inc. DS39632E-page 339 PIC18F2455/2550/4455/4550 MOVLW Move Literal to W Syntax: MOVLW k Operands: 0 ≤ k ≤ 255 Operation: k → W Status Affected: None Encoding: 0000 1110 kkkk kkkk Description: The eight-bit literal ‘k’ is loaded into W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example: MOVLW 5Ah After Instruction W = 5Ah MOVWF Move W to f Syntax: MOVWF f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (W) → f Status Affected: None Encoding: 0110 111a ffff ffff Description: Move data from W to register ‘f’. Location ‘f’ can be anywhere in the 256-byte bank. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: MOVWF REG, 0 Before Instruction W = 4Fh REG = FFh After Instruction W = 4Fh REG = 4Fh PIC18F2455/2550/4455/4550 DS39632E-page 340 © 2009 Microchip Technology Inc. MULLW Multiply Literal with W Syntax: MULLW k Operands: 0 ≤ k ≤ 255 Operation: (W) x k → PRODH:PRODL Status Affected: None Encoding: 0000 1101 kkkk kkkk Description: An unsigned multiplication is carried out between the contents of W and the 8-bit literal ‘k’. The 16-bit result is placed in PRODH:PRODL register pair. PRODH contains the high byte. W is unchanged. None of the Status flags are affected. Note that neither Overflow nor Carry is possible in this operation. A zero result is possible but not detected. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write registers PRODH: PRODL Example: MULLW 0C4h Before Instruction W = E2h PRODH = ? PRODL = ? After Instruction W = E2h PRODH = ADh PRODL = 08h MULWF Multiply W with f Syntax: MULWF f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (W) x (f) → PRODH:PRODL Status Affected: None Encoding: 0000 001a ffff ffff Description: An unsigned multiplication is carried out between the contents of W and the register file location ‘f’. The 16-bit result is stored in the PRODH:PRODL register pair. PRODH contains the high byte. Both W and ‘f’ are unchanged. None of the Status flags are affected. Note that neither Overflow nor Carry is possible in this operation. A Zero result is possible but not detected. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write registers PRODH: PRODL Example: MULWF REG, 1 Before Instruction W = C4h REG = B5h PRODH = ? PRODL = ? After Instruction W = C4h REG = B5h PRODH = 8Ah PRODL = 94h © 2009 Microchip Technology Inc. DS39632E-page 341 PIC18F2455/2550/4455/4550 NEGF Negate f Syntax: NEGF f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: (f) + 1 → f Status Affected: N, OV, C, DC, Z Encoding: 0110 110a ffff ffff Description: Location ‘f’ is negated using two’s complement. The result is placed in the data memory location ‘f’. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: NEGF REG, 1 Before Instruction REG = 0011 1010 [3Ah] After Instruction REG = 1100 0110 [C6h] NOP No Operation Syntax: NOP Operands: None Operation: No operation Status Affected: None Encoding: 0000 1111 0000 xxxx 0000 xxxx 0000 xxxx Description: No operation. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation No operation No operation Example: None. PIC18F2455/2550/4455/4550 DS39632E-page 342 © 2009 Microchip Technology Inc. POP Pop Top of Return Stack Syntax: POP Operands: None Operation: (TOS) → bit bucket Status Affected: None Encoding: 0000 0000 0000 0110 Description: The TOS value is pulled off the return stack and is discarded. The TOS value then becomes the previous value that was pushed onto the return stack. This instruction is provided to enable the user to properly manage the return stack to incorporate a software stack. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation Pop TOS value No operation Example: POP GOTO NEW Before Instruction TOS = 0031A2h Stack (1 level down) = 014332h After Instruction TOS = 014332h PC = NEW PUSH Push Top of Return Stack Syntax: PUSH Operands: None Operation: (PC + 2) → TOS Status Affected: None Encoding: 0000 0000 0000 0101 Description: The PC + 2 is pushed onto the top of the return stack. The previous TOS value is pushed down on the stack. This instruction allows implementing a software stack by modifying TOS and then pushing it onto the return stack. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Push PC + 2 onto return stack No operation No operation Example: PUSH Before Instruction TOS = 345Ah PC = 0124h After Instruction PC = 0126h TOS = 0126h Stack (1 level down) = 345Ah © 2009 Microchip Technology Inc. DS39632E-page 343 PIC18F2455/2550/4455/4550 RCALL Relative Call Syntax: RCALL n Operands: -1024 ≤ n ≤ 1023 Operation: (PC) + 2 → TOS, (PC) + 2 + 2n → PC Status Affected: None Encoding: 1101 1nnn nnnn nnnn Description: Subroutine call with a jump up to 1K from the current location. First, return address (PC + 2) is pushed onto the stack. Then, add the 2’s complement number ‘2n’ to the PC. Since the PC will have incremented to fetch the next instruction, the new address will be PC + 2 + 2n. This instruction is a two-cycle instruction. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘n’ Push PC to stack Process Data Write to PC No operation No operation No operation No operation Example: HERE RCALL Jump Before Instruction PC = Address (HERE) After Instruction PC = Address (Jump) TOS = Address (HERE + 2) RESET Reset Syntax: RESET Operands: None Operation: Reset all registers and flags that are affected by a MCLR Reset. Status Affected: All Encoding: 0000 0000 1111 1111 Description: This instruction provides a way to execute a MCLR Reset in software. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Start Reset No operation No operation Example: RESET After Instruction Registers = Reset Value Flags* = Reset Value PIC18F2455/2550/4455/4550 DS39632E-page 344 © 2009 Microchip Technology Inc. RETFIE Return from Interrupt Syntax: RETFIE {s} Operands: s ∈ [0,1] Operation: (TOS) → PC, 1 → GIE/GIEH or PEIE/GIEL; if s = 1, (WS) → W, (STATUSS) → STATUS, (BSRS) → BSR, PCLATU, PCLATH are unchanged Status Affected: GIE/GIEH, PEIE/GIEL. Encoding: 0000 0000 0001 000s Description: Return from interrupt. Stack is popped and Top-of-Stack (TOS) is loaded into the PC. Interrupts are enabled by setting either the high or low-priority global interrupt enable bit. If ‘s’ = 1, the contents of the shadow registers WS, STATUSS and BSRS are loaded into their corresponding registers, W, STATUS and BSR. If ‘s’ = 0, no update of these registers occurs (default). Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation No operation Pop PC from stack Set GIEH or GIEL No operation No operation No operation No operation Example: RETFIE 1 After Interrupt PC = TOS W = WS BSR = BSRS STATUS = STATUSS GIE/GIEH, PEIE/GIEL = 1 RETLW Return Literal to W Syntax: RETLW k Operands: 0 ≤ k ≤ 255 Operation: k → W, (TOS) → PC, PCLATU, PCLATH are unchanged Status Affected: None Encoding: 0000 1100 kkkk kkkk Description: W is loaded with the eight-bit literal ‘k’. The program counter is loaded from the top of the stack (the return address). The high address latch (PCLATH) remains unchanged. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Pop PC from stack, Write to W No operation No operation No operation No operation Example: CALL TABLE ; W contains table ; offset value ; W now has ; table value : TABLE ADDWF PCL ; W = offset RETLW k0 ; Begin table RETLW k1 ; : : RETLW kn ; End of table Before Instruction W = 07h After Instruction W = value of kn © 2009 Microchip Technology Inc. DS39632E-page 345 PIC18F2455/2550/4455/4550 RETURN Return from Subroutine Syntax: RETURN {s} Operands: s ∈ [0,1] Operation: (TOS) → PC; if s = 1, (WS) → W, (STATUSS) → STATUS, (BSRS) → BSR, PCLATU, PCLATH are unchanged Status Affected: None Encoding: 0000 0000 0001 001s Description: Return from subroutine. The stack is popped and the top of the stack (TOS) is loaded into the program counter. If ‘s’= 1, the contents of the shadow registers WS, STATUSS and BSRS are loaded into their corresponding registers, W, STATUS and BSR. If ‘s’ = 0, no update of these registers occurs (default). Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation Process Data Pop PC from stack No operation No operation No operation No operation Example: RETURN After Instruction: PC = TOS RLCF Rotate Left f through Carry Syntax: RLCF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) → dest, (f<7>) → C, (C) → dest<0> Status Affected: C, N, Z Encoding: 0011 01da ffff ffff Description: The contents of register ‘f’ are rotated one bit to the left through the Carry flag. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: RLCF REG, 0, 0 Before Instruction REG = 1110 0110 C = 0 After Instruction REG = 1110 0110 W = 1100 1100 C = 1 C register f PIC18F2455/2550/4455/4550 DS39632E-page 346 © 2009 Microchip Technology Inc. RLNCF Rotate Left f (No Carry) Syntax: RLNCF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) → dest, (f<7>) → dest<0> Status Affected: N, Z Encoding: 0100 01da ffff ffff Description: The contents of register ‘f’ are rotated one bit to the left. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: RLNCF REG, 1, 0 Before Instruction REG = 1010 1011 After Instruction REG = 0101 0111 register f RRCF Rotate Right f through Carry Syntax: RRCF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) → dest, (f<0>) → C, (C) → dest<7> Status Affected: C, N, Z Encoding: 0011 00da ffff ffff Description: The contents of register ‘f’ are rotated one bit to the right through the Carry flag. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: RRCF REG, 0, 0 Before Instruction REG = 1110 0110 C = 0 After Instruction REG = 1110 0110 W = 0111 0011 C = 0 C register f © 2009 Microchip Technology Inc. DS39632E-page 347 PIC18F2455/2550/4455/4550 RRNCF Rotate Right f (No Carry) Syntax: RRNCF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) → dest, (f<0>) → dest<7> Status Affected: N, Z Encoding: 0100 00da ffff ffff Description: The contents of register ‘f’ are rotated one bit to the right. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank will be selected, overriding the BSR value. If ‘a’ is ‘1’, then the bank will be selected as per the BSR value (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example 1: RRNCF REG, 1, 0 Before Instruction REG = 1101 0111 After Instruction REG = 1110 1011 Example 2: RRNCF REG, 0, 0 Before Instruction W = ? REG = 1101 0111 After Instruction W = 1110 1011 REG = 1101 0111 register f SETF Set f Syntax: SETF f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: FFh → f Status Affected: None Encoding: 0110 100a ffff ffff Description: The contents of the specified register are set to FFh. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write register ‘f’ Example: SETF REG,1 Before Instruction REG = 5Ah After Instruction REG = FFh PIC18F2455/2550/4455/4550 DS39632E-page 348 © 2009 Microchip Technology Inc. SLEEP Enter Sleep mode Syntax: SLEEP Operands: None Operation: 00h → WDT, 0 → WDT postscaler, 1 → TO, 0 → PD Status Affected: TO, PD Encoding: 0000 0000 0000 0011 Description: The Power-Down status bit (PD) is cleared. The Time-out status bit (TO) is set. Watchdog Timer and its postscaler are cleared. The processor is put into Sleep mode with the oscillator stopped. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation Process Data Go to Sleep Example: SLEEP Before Instruction TO = ? PD = ? After Instruction TO = 1 † PD = 0 † If WDT causes wake-up, this bit is cleared. SUBFWB Subtract f from W with Borrow Syntax: SUBFWB f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) – (f) – (C) → dest Status Affected: N, OV, C, DC, Z Encoding: 0101 01da ffff ffff Description: Subtract register ‘f’ and Carry flag (borrow) from W (2’s complement method). If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example 1: SUBFWB REG, 1, 0 Before Instruction REG = 3 W = 2 C = 1 After Instruction REG = FF W = 2 C = 0 Z = 0 N = 1 ; result is negative Example 2: SUBFWB REG, 0, 0 Before Instruction REG = 2 W = 5 C = 1 After Instruction REG = 2 W = 3 C = 1 Z = 0 N = 0 ; result is positive Example 3: SUBFWB REG, 1, 0 Before Instruction REG = 1 W = 2 C = 0 After Instruction REG = 0 W = 2 C = 1 Z = 1 ; result is zero N = 0 © 2009 Microchip Technology Inc. DS39632E-page 349 PIC18F2455/2550/4455/4550 SUBLW Subtract W from Literal Syntax: SUBLW k Operands: 0 ≤ k ≤ 255 Operation: k – (W) → W Status Affected: N, OV, C, DC, Z Encoding: 0000 1000 kkkk kkkk Description W is subtracted from the eight-bit literal ‘k’. The result is placed in W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example 1: SUBLW 02h Before Instruction W = 01h C = ? After Instruction W = 01h C = 1 ; result is positive Z = 0 N = 0 Example 2: SUBLW 02h Before Instruction W = 02h C = ? After Instruction W = 00h C = 1 ; result is zero Z = 1 N = 0 Example 3: SUBLW 02h Before Instruction W = 03h C = ? After Instruction W = FFh ; (2’s complement) C = 0 ; result is negative Z = 0 N = 1 SUBWF Subtract W from f Syntax: SUBWF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) – (W) → dest Status Affected: N, OV, C, DC, Z Encoding: 0101 11da ffff ffff Description: Subtract W from register ‘f’ (2’s complement method). If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example 1: SUBWF REG, 1, 0 Before Instruction REG = 3 W = 2 C = ? After Instruction REG = 1 W = 2 C = 1 ; result is positive Z = 0 N = 0 Example 2: SUBWF REG, 0, 0 Before Instruction REG = 2 W = 2 C = ? After Instruction REG = 2 W = 0 C = 1 ; result is zero Z = 1 N = 0 Example 3: SUBWF REG, 1, 0 Before Instruction REG = 1 W = 2 C = ? After Instruction REG = FFh ;(2’s complement) W = 2 C = 0 ; result is negative Z = 0 N = 1 PIC18F2455/2550/4455/4550 DS39632E-page 350 © 2009 Microchip Technology Inc. SUBWFB Subtract W from f with Borrow Syntax: SUBWFB f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f) – (W) – (C) → dest Status Affected: N, OV, C, DC, Z Encoding: 0101 10da ffff ffff Description: Subtract W and the Carry flag (borrow) from register ‘f’ (2’s complement method). If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example 1: SUBWFB REG, 1, 0 Before Instruction REG = 19h (0001 1001) W = 0Dh (0000 1101) C = 1 After Instruction REG = 0Ch (0000 1011) W = 0Dh (0000 1101) C = 1 Z = 0 N = 0 ; result is positive Example 2: SUBWFB REG, 0, 0 Before Instruction REG = 1Bh (0001 1011) W = 1Ah (0001 1010) C = 0 After Instruction REG = 1Bh (0001 1011) W = 00h C = 1 Z = 1 ; result is zero N = 0 Example 3: SUBWFB REG, 1, 0 Before Instruction REG = 03h (0000 0011) W = 0Eh (0000 1101) C = 1 After Instruction REG = F5h (1111 0100) ; [2’s comp] W = 0Eh (0000 1101) C = 0 Z = 0 N = 1 ; result is negative SWAPF Swap f Syntax: SWAPF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (f<3:0>) → dest<7:4>, (f<7:4>) → dest<3:0> Status Affected: None Encoding: 0011 10da ffff ffff Description: The upper and lower nibbles of register ‘f’ are exchanged. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is placed in register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: SWAPF REG, 1, 0 Before Instruction REG = 53h After Instruction REG = 35h © 2009 Microchip Technology Inc. DS39632E-page 351 PIC18F2455/2550/4455/4550 TBLRD Table Read Syntax: TBLRD ( *; *+; *-; +*) Operands: None Operation: if TBLRD *, (Prog Mem (TBLPTR)) → TABLAT, TBLPTR – No Change; if TBLRD *+, (Prog Mem (TBLPTR)) → TABLAT, (TBLPTR) + 1 → TBLPTR; if TBLRD *-, (Prog Mem (TBLPTR)) → TABLAT, (TBLPTR) – 1 → TBLPTR; if TBLRD +*, (TBLPTR) + 1 → TBLPTR, (Prog Mem (TBLPTR)) → TABLAT Status Affected: None Encoding: 0000 0000 0000 10nn nn=0 * =1 *+ =2 *- =3 +* Description: This instruction is used to read the contents of Program Memory (P.M.). To address the program memory, a pointer called Table Pointer (TBLPTR) is used. The TBLPTR (a 21-bit pointer) points to each byte in the program memory. TBLPTR has a 2-Mbyte address range. TBLPTR[0] = 0: Least Significant Byte of Program Memory Word TBLPTR[0] = 1: Most Significant Byte of Program Memory Word The TBLRD instruction can modify the value of TBLPTR as follows: • no change • post-increment • post-decrement • pre-increment Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation No operation No operation No operation No operation (Read Program Memory) No operation No operation (Write TABLAT) TBLRD Table Read (Continued) Example 1: TBLRD *+ ; Before Instruction TABLAT = 55h TBLPTR = 00A356h MEMORY (00A356h) = 34h After Instruction TABLAT = 34h TBLPTR = 00A357h Example 2: TBLRD +* ; Before Instruction TABLAT = AAh TBLPTR = 01A357h MEMORY (01A357h) = 12h MEMORY (01A358h) = 34h After Instruction TABLAT = 34h TBLPTR = 01A358h PIC18F2455/2550/4455/4550 DS39632E-page 352 © 2009 Microchip Technology Inc. TBLWT Table Write Syntax: TBLWT ( *; *+; *-; +*) Operands: None Operation: if TBLWT*, (TABLAT) → Holding Register, TBLPTR – No Change; if TBLWT*+, (TABLAT) → Holding Register, (TBLPTR) + 1 → TBLPTR; if TBLWT*-, (TABLAT) → Holding Register, (TBLPTR) – 1 → TBLPTR; if TBLWT+*, (TBLPTR) + 1 → TBLPTR; (TABLAT) → Holding Register Status Affected: None Encoding: 0000 0000 0000 11nn nn=0 * =1 *+ =2 *- =3 +* Description: This instruction uses the 3 LSBs of TBLPTR to determine which of the 8 holding registers the TABLAT is written to. The holding registers are used to program the contents of Program Memory (P.M.). (Refer to Section 6.0 “Flash Program Memory” for additional details on programming Flash memory.) The TBLPTR (a 21-bit pointer) points to each byte in the program memory. TBLPTR has a 2-Mbyte address range. The LSb of the TBLPTR selects which byte of the program memory location to access. TBLPTR[0] = 0: Least Significant Byte of Program Memory Word TBLPTR[0] = 1: Most Significant Byte of Program Memory Word The TBLWT instruction can modify the value of TBLPTR as follows: • no change • post-increment • post-decrement • pre-increment Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode No operation No operation No operation No operation No operation (Read TABLAT) No operation No operation (Write to Holding Register) TBLWT Table Write (Continued) Example 1: TBLWT *+; Before Instruction TABLAT = 55h TBLPTR = 00A356h HOLDING REGISTER (00A356h) = FFh After Instructions (table write completion) TABLAT = 55h TBLPTR = 00A357h HOLDING REGISTER (00A356h) = 55h Example 2: TBLWT +*; Before Instruction TABLAT = 34h TBLPTR = 01389Ah HOLDING REGISTER (01389Ah) = FFh HOLDING REGISTER (01389Bh) = FFh After Instruction (table write completion) TABLAT = 34h TBLPTR = 01389Bh HOLDING REGISTER (01389Ah) = FFh HOLDING REGISTER (01389Bh) = 34h © 2009 Microchip Technology Inc. DS39632E-page 353 PIC18F2455/2550/4455/4550 TSTFSZ Test f, Skip if 0 Syntax: TSTFSZ f {,a} Operands: 0 ≤ f ≤ 255 a ∈ [0,1] Operation: skip if f = 0 Status Affected: None Encoding: 0110 011a ffff ffff Description: If ‘f’ = 0, the next instruction fetched during the current instruction execution is discarded and a NOP is executed, making this a two-cycle instruction. If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1(2) Note: 3 cycles if skip and followed by a 2-word instruction. Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data No operation If skip: Q1 Q2 Q3 Q4 No operation No operation No operation No operation If skip and followed by 2-word instruction: Q1 Q2 Q3 Q4 No operation No operation No operation No operation No operation No operation No operation No operation Example: HERE TSTFSZ CNT, 1 NZERO : ZERO : Before Instruction PC = Address (HERE) After Instruction If CNT = 00h, PC = Address (ZERO) If CNT ≠ 00h, PC = Address (NZERO) XORLW Exclusive OR Literal with W Syntax: XORLW k Operands: 0 ≤ k ≤ 255 Operation: (W) .XOR. k → W Status Affected: N, Z Encoding: 0000 1010 kkkk kkkk Description: The contents of W are XORed with the 8-bit literal ‘k’. The result is placed in W. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to W Example: XORLW 0AFh Before Instruction W = B5h After Instruction W = 1Ah PIC18F2455/2550/4455/4550 DS39632E-page 354 © 2009 Microchip Technology Inc. XORWF Exclusive OR W with f Syntax: XORWF f {,d {,a}} Operands: 0 ≤ f ≤ 255 d ∈ [0,1] a ∈ [0,1] Operation: (W) .XOR. (f) → dest Status Affected: N, Z Encoding: 0001 10da ffff ffff Description: Exclusive OR the contents of W with register ‘f’. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in the register ‘f’ (default). If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘1’, the BSR is used to select the GPR bank (default). If ‘a’ is ‘0’ and the extended instruction set is enabled, this instruction operates in Indexed Literal Offset Addressing mode whenever f ≤ 95 (5Fh). See Section 26.2.3 “Byte-Oriented and Bit-Oriented Instructions in Indexed Literal Offset Mode” for details. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: XORWF REG, 1, 0 Before Instruction REG = AFh W = B5h After Instruction REG = 1Ah W = B5h © 2009 Microchip Technology Inc. DS39632E-page 355 PIC18F2455/2550/4455/4550 26.2 Extended Instruction Set In addition to the standard 75 instructions of the PIC18 instruction set, PIC18F2455/2550/4455/4550 devices also provide an optional extension to the core CPU functionality. The added features include eight additional instructions that augment Indirect and Indexed Addressing operations and the implementation of Indexed Literal Offset Addressing mode for many of the standard PIC18 instructions. The additional features of the extended instruction set are disabled by default. To enable them, users must set the XINST Configuration bit. The instructions in the extended set can all be classified as literal operations, which either manipulate the File Select Registers, or use them for Indexed Addressing. Two of the instructions, ADDFSR and SUBFSR, each have an additional special instantiation for using FSR2. These versions (ADDULNK and SUBULNK) allow for automatic return after execution. The extended instructions are specifically implemented to optimize re-entrant program code (that is, code that is recursive or that uses a software stack) written in high-level languages, particularly C. Among other things, they allow users working in high-level languages to perform certain operations on data structures more efficiently. These include: • Dynamic allocation and deallocation of software stack space when entering and leaving subroutines • Function Pointer invocation • Software Stack Pointer manipulation • Manipulation of variables located in a software stack A summary of the instructions in the extended instruction set is provided in Table 26-3. Detailed descriptions are provided in Section 26.2.2 “Extended Instruction Set”. The opcode field descriptions in Table 26-1 (page 314) apply to both the standard and extended PIC18 instruction sets. 26.2.1 EXTENDED INSTRUCTION SYNTAX Most of the extended instructions use indexed arguments, using one of the File Select Registers and some offset to specify a source or destination register. When an argument for an instruction serves as part of Indexed Addressing, it is enclosed in square brackets (“[ ]”). This is done to indicate that the argument is used as an index or offset. The MPASM™ Assembler will flag an error if it determines that an index or offset value is not bracketed. When the extended instruction set is enabled, brackets are also used to indicate index arguments in byteoriented and bit-oriented instructions. This is in addition to other changes in their syntax. For more details, see Section 26.2.3.1 “Extended Instruction Syntax with Standard PIC18 Commands”. TABLE 26-3: EXTENSIONS TO THE PIC18 INSTRUCTION SET Note: The instruction set extension and the Indexed Literal Offset Addressing mode were designed for optimizing applications written in C; the user may likely never use these instructions directly in assembler. The syntax for these commands is provided as a reference for users who may be reviewing code that has been generated by a compiler. Note: In the past, square brackets have been used to denote optional arguments in the PIC18 and earlier instruction sets. In this text and going forward, optional arguments are denoted by braces (“{ }”). Mnemonic, Operands Description Cycles 16-Bit Instruction Word Status MSb LSb Affected ADDFSR ADDULNK CALLW MOVSF MOVSS PUSHL SUBFSR SUBULNK f, k k zs, fd zs, zd k f, k k Add Literal to FSR Add Literal to FSR2 and Return Call Subroutine using WREG Move zs (source) to 1st word fd (destination) 2nd word Move zs (source) to 1st word zd (destination) 2nd word Store Literal at FSR2, Decrement FSR2 Subtract Literal from FSR Subtract Literal from FSR2 and Return 1222 2 1 12 1110 1110 0000 1110 1111 1110 1111 1110 1110 1110 1000 1000 0000 1011 ffff 1011 xxxx 1010 1001 1001 ffkk 11kk 0001 0zzz ffff 1zzz xzzz kkkk ffkk 11kk kkkk kkkk 0100 zzzz ffff zzzz zzzz kkkk kkkk kkkk None None None None None None None None PIC18F2455/2550/4455/4550 DS39632E-page 356 © 2009 Microchip Technology Inc. 26.2.2 EXTENDED INSTRUCTION SET ADDFSR Add Literal to FSR Syntax: ADDFSR f, k Operands: 0 ≤ k ≤ 63 f ∈ [ 0, 1, 2 ] Operation: FSR(f) + k → FSR(f) Status Affected: None Encoding: 1110 1000 ffkk kkkk Description: The 6-bit literal ‘k’ is added to the contents of the FSR specified by ‘f’. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to FSR Example: ADDFSR 2, 23h Before Instruction FSR2 = 03FFh After Instruction FSR2 = 0422h ADDULNK Add Literal to FSR2 and Return Syntax: ADDULNK k Operands: 0 ≤ k ≤ 63 Operation: FSR2 + k → FSR2, (TOS) → PC Status Affected: None Encoding: 1110 1000 11kk kkkk Description: The 6-bit literal ‘k’ is added to the contents of FSR2. A RETURN is then executed by loading the PC with the TOS. The instruction takes two cycles to execute; a NOP is performed during the second cycle. This may be thought of as a special case of the ADDFSR instruction, where f = 3 (binary ‘11’); it operates only on FSR2. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read literal ‘k’ Process Data Write to FSR No Operation No Operation No Operation No Operation Example: ADDULNK 23h Before Instruction FSR2 = 03FFh PC = 0100h After Instruction FSR2 = 0422h PC = (TOS) Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in symbolic addressing. If a label is used, the instruction syntax then becomes: {label} instruction argument(s). © 2009 Microchip Technology Inc. DS39632E-page 357 PIC18F2455/2550/4455/4550 CALLW Subroutine Call Using WREG Syntax: CALLW Operands: None Operation: (PC + 2) → TOS, (W) → PCL, (PCLATH) → PCH, (PCLATU) → PCU Status Affected: None Encoding: 0000 0000 0001 0100 Description First, the return address (PC + 2) is pushed onto the return stack. Next, the contents of W are written to PCL; the existing value is discarded. Then the contents of PCLATH and PCLATU are latched into PCH and PCU, respectively. The second cycle is executed as a NOP instruction while the new next instruction is fetched. Unlike CALL, there is no option to update W, STATUS or BSR. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read WREG Push PC to stack No operation No operation No operation No operation No operation Example: HERE CALLW Before Instruction PC = address (HERE) PCLATH = 10h PCLATU = 00h W = 06h After Instruction PC = 001006h TOS = address (HERE + 2) PCLATH = 10h PCLATU = 00h W = 06h MOVSF Move Indexed to f Syntax: MOVSF [zs], fd Operands: 0 ≤ zs ≤ 127 0 ≤ fd ≤ 4095 Operation: ((FSR2) + zs) → fd Status Affected: None Encoding: 1st word (source) 2nd word (destin.) 1110 1111 1011 ffff 0zzz ffff zzzzs ffffd Description: The contents of the source register are moved to destination register ‘fd’. The actual address of the source register is determined by adding the 7-bit literal offset ‘zs’ in the first word to the value of FSR2. The address of the destination register is specified by the 12-bit literal ‘fd’ in the second word. Both addresses can be anywhere in the 4096-byte data space (000h to FFFh). The MOVSF instruction cannot use the PCL, TOSU, TOSH or TOSL as the destination register. If the resultant source address points to an indirect addressing register, the value returned will be 00h. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Determine source addr Determine source addr Read source reg Decode No operation No dummy read No operation Write register ‘f’ (dest) Example: MOVSF [05h], REG2 Before Instruction FSR2 = 80h Contents of 85h = 33h REG2 = 11h After Instruction FSR2 = 80h Contents of 85h = 33h REG2 = 33h PIC18F2455/2550/4455/4550 DS39632E-page 358 © 2009 Microchip Technology Inc. MOVSS Move Indexed to Indexed Syntax: MOVSS [zs], [zd] Operands: 0 ≤ zs ≤ 127 0 ≤ zd ≤ 127 Operation: ((FSR2) + zs) → ((FSR2) + zd) Status Affected: None Encoding: 1st word (source) 2nd word (dest.) 1110 1111 1011 xxxx 1zzz xzzz zzzzs zzzzd Description The contents of the source register are moved to the destination register. The addresses of the source and destination registers are determined by adding the 7-bit literal offsets ‘zs’ or ‘zd’, respectively, to the value of FSR2. Both registers can be located anywhere in the 4096-byte data memory space (000h to FFFh). The MOVSS instruction cannot use the PCL, TOSU, TOSH or TOSL as the destination register. If the resultant source address points to an indirect addressing register, the value returned will be 00h. If the resultant destination address points to an indirect addressing register, the instruction will execute as a NOP. Words: 2 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Determine source addr Determine source addr Read source reg Decode Determine dest addr Determine dest addr Write to dest reg Example: MOVSS [05h], [06h] Before Instruction FSR2 = 80h Contents of 85h = 33h Contents of 86h = 11h After Instruction FSR2 = 80h Contents of 85h = 33h Contents of 86h = 33h PUSHL Store Literal at FSR2, Decrement FSR2 Syntax: PUSHL k Operands: 0 ≤ k ≤ 255 Operation: k → (FSR2), FSR2 – 1→ FSR2 Status Affected: None Encoding: 1110 1010 kkkk kkkk Description: The 8-bit literal ‘k’ is written to the data memory address specified by FSR2. FSR2 is decremented by ‘1’ after the operation. This instruction allows users to push values onto a software stack. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read ‘k’ Process data Write to destination Example: PUSHL 08h Before Instruction FSR2H:FSR2L = 01ECh Memory (01ECh) = 00h After Instruction FSR2H:FSR2L = 01EBh Memory (01ECh) = 08h © 2009 Microchip Technology Inc. DS39632E-page 359 PIC18F2455/2550/4455/4550 SUBFSR Subtract Literal from FSR Syntax: SUBFSR f, k Operands: 0 ≤ k ≤ 63 f ∈ [ 0, 1, 2 ] Operation: FSRf – k → FSRf Status Affected: None Encoding: 1110 1001 ffkk kkkk Description: The 6-bit literal ‘k’ is subtracted from the contents of the FSR specified by ‘f’. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: SUBFSR 2, 23h Before Instruction FSR2 = 03FFh After Instruction FSR2 = 03DCh SUBULNK Subtract Literal from FSR2 and Return Syntax: SUBULNK k Operands: 0 ≤ k ≤ 63 Operation: FSR2 – k → FSR2, (TOS) → PC Status Affected: None Encoding: 1110 1001 11kk kkkk Description: The 6-bit literal ‘k’ is subtracted from the contents of the FSR2. A RETURN is then executed by loading the PC with the TOS. The instruction takes two cycles to execute; a NOP is performed during the second cycle. This may be thought of as a special case of the SUBFSR instruction, where f = 3 (binary ‘11’); it operates only on FSR2. Words: 1 Cycles: 2 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination No Operation No Operation No Operation No Operation Example: SUBULNK 23h Before Instruction FSR2 = 03FFh PC = 0100h After Instruction FSR2 = 03DCh PC = (TOS) PIC18F2455/2550/4455/4550 DS39632E-page 360 © 2009 Microchip Technology Inc. 26.2.3 BYTE-ORIENTED AND BIT-ORIENTED INSTRUCTIONS IN INDEXED LITERAL OFFSET MODE In addition to eight new commands in the extended set, enabling the extended instruction set also enables Indexed Literal Offset Addressing mode (Section 5.6.1 “Indexed Addressing with Literal Offset”). This has a significant impact on the way that many commands of the standard PIC18 instruction set are interpreted. When the extended set is disabled, addresses embedded in opcodes are treated as literal memory locations: either as a location in the Access Bank (‘a’ = 0) or in a GPR bank designated by the BSR (‘a’ = 1). When the extended instruction set is enabled and ‘a’ = 0, however, a file register argument of 5Fh or less is interpreted as an offset from the pointer value in FSR2 and not as a literal address. For practical purposes, this means that all instructions that use the Access RAM bit as an argument – that is, all byte-oriented and bitoriented instructions, or almost half of the core PIC18 instructions – may behave differently when the extended instruction set is enabled. When the content of FSR2 is 00h, the boundaries of the Access RAM are essentially remapped to their original values. This may be useful in creating backward compatible code. If this technique is used, it may be necessary to save the value of FSR2 and restore it when moving back and forth between C and assembly routines in order to preserve the Stack Pointer. Users must also keep in mind the syntax requirements of the extended instruction set (see Section 26.2.3.1 “Extended Instruction Syntax with Standard PIC18 Commands”). Although the Indexed Literal Offset Addressing mode can be very useful for dynamic stack and pointer manipulation, it can also be very annoying if a simple arithmetic operation is carried out on the wrong register. Users who are accustomed to the PIC18 programming must keep in mind that, when the extended instruction set is enabled, register addresses of 5Fh or less are used for Indexed Literal Offset Addressing. Representative examples of typical byte-oriented and bit-oriented instructions in the Indexed Literal Offset Addressing mode are provided on the following page to show how execution is affected. The operand conditions shown in the examples are applicable to all instructions of these types. 26.2.3.1 Extended Instruction Syntax with Standard PIC18 Commands When the extended instruction set is enabled, the file register argument, ‘f’, in the standard byte-oriented and bit-oriented commands is replaced with the literal offset value, ‘k’. As already noted, this occurs only when ‘f’ is less than or equal to 5Fh. When an offset value is used, it must be indicated by square brackets (“[ ]”). As with the extended instructions, the use of brackets indicates to the compiler that the value is to be interpreted as an index or an offset. Omitting the brackets, or using a value greater than 5Fh within brackets, will generate an error in the MPASM Assembler. If the index argument is properly bracketed for Indexed Literal Offset Addressing mode, the Access RAM argument is never specified; it will automatically be assumed to be ‘0’. This is in contrast to standard operation (extended instruction set disabled) when ‘a’ is set on the basis of the target address. Declaring the Access RAM bit in this mode will also generate an error in the MPASM Assembler. The destination argument, ‘d’, functions as before. In the latest versions of the MPASM assembler, language support for the extended instruction set must be explicitly invoked. This is done with either the command line option, /y, or the PE directive in the source listing. 26.2.4 CONSIDERATIONS WHEN ENABLING THE EXTENDED INSTRUCTION SET It is important to note that the extensions to the instruction set may not be beneficial to all users. In particular, users who are not writing code that uses a software stack may not benefit from using the extensions to the instruction set. Additionally, the Indexed Literal Offset Addressing mode may create issues with legacy applications written to the PIC18 assembler. This is because instructions in the legacy code may attempt to address registers in the Access Bank below 5Fh. Since these addresses are interpreted as literal offsets to FSR2 when the instruction set extension is enabled, the application may read or write to the wrong data addresses. When porting an application to the PIC18F2455/2550/ 4455/4550, it is very important to consider the type of code. A large, re-entrant application that is written in ‘C’ and would benefit from efficient compilation will do well when using the instruction set extensions. Legacy applications that heavily use the Access Bank will most likely not benefit from using the extended instruction set. Note: Enabling the PIC18 instruction set extension may cause legacy applications to behave erratically or fail entirely. © 2009 Microchip Technology Inc. DS39632E-page 361 PIC18F2455/2550/4455/4550 ADDWF ADD W to Indexed (Indexed Literal Offset mode) Syntax: ADDWF [k] {,d} Operands: 0 ≤ k ≤ 95 d ∈ [0,1] Operation: (W) + ((FSR2) + k) → dest Status Affected: N, OV, C, DC, Z Encoding: 0010 01d0 kkkk kkkk Description: The contents of W are added to the contents of the register indicated by FSR2, offset by the value ‘k’. If ‘d’ is ‘0’, the result is stored in W. If ‘d’ is ‘1’, the result is stored back in register ‘f’ (default). Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read ‘k’ Process Data Write to destination Example: ADDWF [OFST] ,0 Before Instruction W = 17h OFST = 2Ch FSR2 = 0A00h Contents of 0A2Ch = 20h After Instruction W = 37h Contents of 0A2Ch = 20h BSF Bit Set Indexed (Indexed Literal Offset mode) Syntax: BSF [k], b Operands: 0 ≤ f ≤ 95 0 ≤ b ≤ 7 Operation: 1 → ((FSR2) + k) Status Affected: None Encoding: 1000 bbb0 kkkk kkkk Description: Bit ‘b’ of the register indicated by FSR2, offset by the value ‘k’, is set. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read register ‘f’ Process Data Write to destination Example: BSF [FLAG_OFST], 7 Before Instruction FLAG_OFST = 0Ah FSR2 = 0A00h Contents of 0A0Ah = 55h After Instruction Contents of 0A0Ah = D5h SETF Set Indexed (Indexed Literal Offset mode) Syntax: SETF [k] Operands: 0 ≤ k ≤ 95 Operation: FFh → ((FSR2) + k) Status Affected: None Encoding: 0110 1000 kkkk kkkk Description: The contents of the register indicated by FSR2, offset by ‘k’, are set to FFh. Words: 1 Cycles: 1 Q Cycle Activity: Q1 Q2 Q3 Q4 Decode Read ‘k’ Process Data Write register Example: SETF [OFST] Before Instruction OFST = 2Ch FSR2 = 0A00h Contents of 0A2Ch = 00h After Instruction Contents of 0A2Ch = FFh PIC18F2455/2550/4455/4550 DS39632E-page 362 © 2009 Microchip Technology Inc. 26.2.5 SPECIAL CONSIDERATIONS WITH MICROCHIP MPLAB® IDE TOOLS The latest versions of Microchip’s software tools have been designed to fully support the extended instruction set of the PIC18F2455/2550/4455/4550 family of devices. This includes the MPLAB C18 C compiler, MPASM Assembly language and MPLAB Integrated Development Environment (IDE). When selecting a target device for software development, MPLAB IDE will automatically set default Configuration bits for that device. The default setting for the XINST Configuration bit is ‘0’, disabling the extended instruction set and Indexed Literal Offset Addressing mode. For proper execution of applications developed to take advantage of the extended instruction set, XINST must be set during programming. To develop software for the extended instruction set, the user must enable support for the instructions and the Indexed Addressing mode in their language tool(s). Depending on the environment being used, this may be done in several ways: • A menu option, or dialog box within the environment, that allows the user to configure the language tool and its settings for the project • A command line option • A directive in the source code These options vary between different compilers, assemblers and development environments. Users are encouraged to review the documentation accompanying their development systems for the appropriate information. © 2009 Microchip Technology Inc. DS39632E-page 363 PIC18F2455/2550/4455/4550 27.0 DEVELOPMENT SUPPORT The PIC® microcontrollers are supported with a full range of hardware and software development tools: • Integrated Development Environment - MPLAB® IDE Software • Assemblers/Compilers/Linkers - MPASMTM Assembler - MPLAB C18 and MPLAB C30 C Compilers - MPLINKTM Object Linker/ MPLIBTM Object Librarian - MPLAB ASM30 Assembler/Linker/Library • Simulators - MPLAB SIM Software Simulator • Emulators - MPLAB ICE 2000 In-Circuit Emulator - MPLAB REAL ICE™ In-Circuit Emulator • In-Circuit Debugger - MPLAB ICD 2 • Device Programmers - PICSTART® Plus Development Programmer - MPLAB PM3 Device Programmer - PICkit™ 2 Development Programmer • Low-Cost Demonstration and Development Boards and Evaluation Kits 27.1 MPLAB Integrated Development Environment Software The MPLAB IDE software brings an ease of software development previously unseen in the 8/16-bit microcontroller market. The MPLAB IDE is a Windows® operating system-based application that contains: • A single graphical interface to all debugging tools - Simulator - Programmer (sold separately) - Emulator (sold separately) - In-Circuit Debugger (sold separately) • A full-featured editor with color-coded context • A multiple project manager • Customizable data windows with direct edit of contents • High-level source code debugging • Visual device initializer for easy register initialization • Mouse over variable inspection • Drag and drop variables from source to watch windows • Extensive on-line help • Integration of select third party tools, such as HI-TECH Software C Compilers and IAR C Compilers The MPLAB IDE allows you to: • Edit your source files (either assembly or C) • One touch assemble (or compile) and download to PIC MCU emulator and simulator tools (automatically updates all project information) • Debug using: - Source files (assembly or C) - Mixed assembly and C - Machine code MPLAB IDE supports multiple debugging tools in a single development paradigm, from the cost-effective simulators, through low-cost in-circuit debuggers, to full-featured emulators. This eliminates the learning curve when upgrading to tools with increased flexibility and power. PIC18F2455/2550/4455/4550 DS39632E-page 364 © 2009 Microchip Technology Inc. 27.2 MPASM Assembler The MPASM Assembler is a full-featured, universal macro assembler for all PIC MCUs. The MPASM Assembler generates relocatable object files for the MPLINK Object Linker, Intel® standard HEX files, MAP files to detail memory usage and symbol reference, absolute LST files that contain source lines and generated machine code and COFF files for debugging. The MPASM Assembler features include: • Integration into MPLAB IDE projects • User-defined macros to streamline assembly code • Conditional assembly for multi-purpose source files • Directives that allow complete control over the assembly process 27.3 MPLAB C18 and MPLAB C30 C Compilers The MPLAB C18 and MPLAB C30 Code Development Systems are complete ANSI C compilers for Microchip’s PIC18 and PIC24 families of microcontrollers and the dsPIC30 and dsPIC33 family of digital signal controllers. These compilers provide powerful integration capabilities, superior code optimization and ease of use not found with other compilers. For easy source level debugging, the compilers provide symbol information that is optimized to the MPLAB IDE debugger. 27.4 MPLINK Object Linker/ MPLIB Object Librarian The MPLINK Object Linker combines relocatable objects created by the MPASM Assembler and the MPLAB C18 C Compiler. It can link relocatable objects from precompiled libraries, using directives from a linker script. The MPLIB Object Librarian manages the creation and modification of library files of precompiled code. When a routine from a library is called from a source file, only the modules that contain that routine will be linked in with the application. This allows large libraries to be used efficiently in many different applications. The object linker/library features include: • Efficient linking of single libraries instead of many smaller files • Enhanced code maintainability by grouping related modules together • Flexible creation of libraries with easy module listing, replacement, deletion and extraction 27.5 MPLAB ASM30 Assembler, Linker and Librarian MPLAB ASM30 Assembler produces relocatable machine code from symbolic assembly language for dsPIC30F devices. MPLAB C30 C Compiler uses the assembler to produce its object file. The assembler generates relocatable object files that can then be archived or linked with other relocatable object files and archives to create an executable file. Notable features of the assembler include: • Support for the entire dsPIC30F instruction set • Support for fixed-point and floating-point data • Command line interface • Rich directive set • Flexible macro language • MPLAB IDE compatibility 27.6 MPLAB SIM Software Simulator The MPLAB SIM Software Simulator allows code development in a PC-hosted environment by simulating the PIC MCUs and dsPIC® DSCs on an instruction level. On any given instruction, the data areas can be examined or modified and stimuli can be applied from a comprehensive stimulus controller. Registers can be logged to files for further run-time analysis. The trace buffer and logic analyzer display extend the power of the simulator to record and track program execution, actions on I/O, most peripherals and internal registers. The MPLAB SIM Software Simulator fully supports symbolic debugging using the MPLAB C18 and MPLAB C30 C Compilers, and the MPASM and MPLAB ASM30 Assemblers. The software simulator offers the flexibility to develop and debug code outside of the hardware laboratory environment, making it an excellent, economical software development tool. © 2009 Microchip Technology Inc. DS39632E-page 365 PIC18F2455/2550/4455/4550 27.7 MPLAB ICE 2000 High-Performance In-Circuit Emulator The MPLAB ICE 2000 In-Circuit Emulator is intended to provide the product development engineer with a complete microcontroller design tool set for PIC microcontrollers. Software control of the MPLAB ICE 2000 In-Circuit Emulator is advanced by the MPLAB Integrated Development Environment, which allows editing, building, downloading and source debugging from a single environment. The MPLAB ICE 2000 is a full-featured emulator system with enhanced trace, trigger and data monitoring features. Interchangeable processor modules allow the system to be easily reconfigured for emulation of different processors. The architecture of the MPLAB ICE 2000 In-Circuit Emulator allows expansion to support new PIC microcontrollers. The MPLAB ICE 2000 In-Circuit Emulator system has been designed as a real-time emulation system with advanced features that are typically found on more expensive development tools. The PC platform and Microsoft® Windows® 32-bit operating system were chosen to best make these features available in a simple, unified application. 27.8 MPLAB REAL ICE In-Circuit Emulator System MPLAB REAL ICE In-Circuit Emulator System is Microchip’s next generation high-speed emulator for Microchip Flash DSC and MCU devices. It debugs and programs PIC® Flash MCUs and dsPIC® Flash DSCs with the easy-to-use, powerful graphical user interface of the MPLAB Integrated Development Environment (IDE), included with each kit. The MPLAB REAL ICE probe is connected to the design engineer’s PC using a high-speed USB 2.0 interface and is connected to the target with either a connector compatible with the popular MPLAB ICD 2 system (RJ11) or with the new high-speed, noise tolerant, Low- Voltage Differential Signal (LVDS) interconnection (CAT5). MPLAB REAL ICE is field upgradeable through future firmware downloads in MPLAB IDE. In upcoming releases of MPLAB IDE, new devices will be supported, and new features will be added, such as software breakpoints and assembly code trace. MPLAB REAL ICE offers significant advantages over competitive emulators including low-cost, full-speed emulation, real-time variable watches, trace analysis, complex breakpoints, a ruggedized probe interface and long (up to three meters) interconnection cables. 27.9 MPLAB ICD 2 In-Circuit Debugger Microchip’s In-Circuit Debugger, MPLAB ICD 2, is a powerful, low-cost, run-time development tool, connecting to the host PC via an RS-232 or high-speed USB interface. This tool is based on the Flash PIC MCUs and can be used to develop for these and other PIC MCUs and dsPIC DSCs. The MPLAB ICD 2 utilizes the in-circuit debugging capability built into the Flash devices. This feature, along with Microchip’s In-Circuit Serial ProgrammingTM (ICSPTM) protocol, offers costeffective, in-circuit Flash debugging from the graphical user interface of the MPLAB Integrated Development Environment. This enables a designer to develop and debug source code by setting breakpoints, single stepping and watching variables, and CPU status and peripheral registers. Running at full speed enables testing hardware and applications in real time. MPLAB ICD 2 also serves as a development programmer for selected PIC devices. 27.10 MPLAB PM3 Device Programmer The MPLAB PM3 Device Programmer is a universal, CE compliant device programmer with programmable voltage verification at VDDMIN and VDDMAX for maximum reliability. It features a large LCD display (128 x 64) for menus and error messages and a modular, detachable socket assembly to support various package types. The ICSP™ cable assembly is included as a standard item. In Stand-Alone mode, the MPLAB PM3 Device Programmer can read, verify and program PIC devices without a PC connection. It can also set code protection in this mode. The MPLAB PM3 connects to the host PC via an RS-232 or USB cable. The MPLAB PM3 has high-speed communications and optimized algorithms for quick programming of large memory devices and incorporates an SD/MMC card for file storage and secure data applications. PIC18F2455/2550/4455/4550 DS39632E-page 366 © 2009 Microchip Technology Inc. 27.11 PICSTART Plus Development Programmer The PICSTART Plus Development Programmer is an easy-to-use, low-cost, prototype programmer. It connects to the PC via a COM (RS-232) port. MPLAB Integrated Development Environment software makes using the programmer simple and efficient. The PICSTART Plus Development Programmer supports most PIC devices in DIP packages up to 40 pins. Larger pin count devices, such as the PIC16C92X and PIC17C76X, may be supported with an adapter socket. The PICSTART Plus Development Programmer is CE compliant. 27.12 PICkit 2 Development Programmer The PICkit™ 2 Development Programmer is a low-cost programmer and selected Flash device debugger with an easy-to-use interface for programming many of Microchip’s baseline, mid-range and PIC18F families of Flash memory microcontrollers. The PICkit 2 Starter Kit includes a prototyping development board, twelve sequential lessons, software and HI-TECH’s PICC™ Lite C compiler, and is designed to help get up to speed quickly using PIC® microcontrollers. The kit provides everything needed to program, evaluate and develop applications using Microchip’s powerful, mid-range Flash memory family of microcontrollers. 27.13 Demonstration, Development and Evaluation Boards A wide variety of demonstration, development and evaluation boards for various PIC MCUs and dsPIC DSCs allows quick application development on fully functional systems. Most boards include prototyping areas for adding custom circuitry and provide application firmware and source code for examination and modification. The boards support a variety of features, including LEDs, temperature sensors, switches, speakers, RS-232 interfaces, LCD displays, potentiometers and additional EEPROM memory. The demonstration and development boards can be used in teaching environments, for prototyping custom circuits and for learning about various microcontroller applications. In addition to the PICDEM™ and dsPICDEM™ demonstration/ development board series of circuits, Microchip has a line of evaluation kits and demonstration software for analog filter design, KEELOQ® security ICs, CAN, IrDA®, PowerSmart battery management, SEEVAL® evaluation system, Sigma-Delta ADC, flow rate sensing, plus many more. Check the Microchip web page (www.microchip.com) for the complete list of demonstration, development and evaluation kits. © 2009 Microchip Technology Inc. DS39632E-page 367 PIC18F2455/2550/4455/4550 28.0 ELECTRICAL CHARACTERISTICS Absolute Maximum Ratings(†) Ambient temperature under bias...............................................................................................................-40°C to +85°C Storage temperature .............................................................................................................................. -65°C to +150°C Voltage on any pin with respect to VSS (except VDD and MCLR) (Note 3) ..................................... -0.3V to (VDD + 0.3V) Voltage on VDD with respect to VSS ......................................................................................................... -0.3V to +7.5V Voltage on MCLR with respect to VSS (Note 2) ......................................................................................... 0V to +13.25V Total power dissipation (Note 1) ...............................................................................................................................1.0W Maximum current out of VSS pin ...........................................................................................................................300 mA Maximum current into VDD pin ..............................................................................................................................250 mA Input clamp current, IIK (VI < 0 or VI > VDD)...................................................................................................................... ±20 mA Output clamp current, IOK (VO < 0 or VO > VDD) .............................................................................................................. ±20 mA Maximum output current sunk by any I/O pin..........................................................................................................25 mA Maximum output current sourced by any I/O pin ....................................................................................................25 mA Maximum current sunk by all ports .......................................................................................................................200 mA Maximum current sourced by all ports ..................................................................................................................200 mA Note 1: Power dissipation is calculated as follows: Pdis = VDD x {IDD – Σ IOH} + Σ {(VDD – VOH) x IOH} + Σ(VOL x IOL) 2: Voltage spikes below VSS at the MCLR/VPP/RE3 pin, inducing currents greater than 80 mA, may cause latch-up. Thus, a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR/VPP/ RE3 pin, rather than pulling this pin directly to VSS. 3: When the internal USB regulator is enabled or VUSB is powered externally, RC4 and RC5 are limited to -0.3V to (VUSB + 0.3V) with respect to VSS. † NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. PIC18F2455/2550/4455/4550 DS39632E-page 368 © 2009 Microchip Technology Inc. FIGURE 28-1: PIC18F2455/2550/4455/4550 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL) FIGURE 28-2: PIC18LF2455/2550/4455/4550 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL LOW VOLTAGE) Frequency Voltage 6.0V 5.5V 4.5V 4.0V 2.0V 48 MHz 5.0V 3.5V 3.0V 2.5V 4.2V Frequency Voltage 6.0V 5.5V 4.5V 4.0V 2.0V 48 MHz 5.0V 3.5V 3.0V 2.5V 4 MHz 4.2V 40 MHz Note 1: VDDAPPMIN is the minimum voltage of the PIC® device in the application. 2: For 2.0 < VDD < 4.2 V, FMAX = (16.36 MHz/V) (VDDAPPMIN - 2.0V) + 4 MHz 3: For VDD ≥ 4.2 V, FMAX = 48 MHz. © 2009 Microchip Technology Inc. DS39632E-page 369 PIC18F2455/2550/4455/4550 28.1 DC Characteristics: Supply Voltage PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Characteristic Min Typ Max Units Conditions D001 VDD Supply Voltage 2.0(2) — 5.5 V EC, HS, XT and Internal Oscillator modes 3.0(2) — 5.5 V HSPLL, XTPLL, ECPIO and ECPLL Oscillator modes D002 VDR RAM Data Retention Voltage(1) 1.5 — — V D003 VPOR VDD Start Voltage to Ensure Internal Power-on Reset Signal — — 0.7 V See Section 4.3 “Power-on Reset (POR)” for details D004 SVDD VDD Rise Rate to Ensure Internal Power-on Reset Signal 0.05 — — V/ms See Section 4.3 “Power-on Reset (POR)” for details D005 VBOR Brown-out Reset Voltage BORV1:BORV0 = 11 2.00 2.05 2.16 V BORV1:BORV0 = 10 2.65 2.79 2.93 V BORV1:BORV0 = 01 4.11 4.33 4.55 V BORV1:BORV0 = 00 4.36 4.59 4.82 V Legend: Shading of rows is to assist in readability of the table. Note 1: This is the limit to which VDD can be lowered in Sleep mode, or during a device Reset, without losing RAM data. 2: The stated minimums apply for the PIC18LF products in this device family. PIC18F products in this device family are rated for 4.2V minimum in all oscillator modes. PIC18F2455/2550/4455/4550 DS39632E-page 370 © 2009 Microchip Technology Inc. 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Power-Down Current (IPD)(1) PIC18LFX455/X550 0.1 0.95 μA -40°C VDD = 2.0V 0.1 1.0 (Sleep mode) μA +25°C 0.2 5 μA +85°C PIC18LFX455/X550 0.1 1.4 μA -40°C VDD = 3.0V 0.1 2 (Sleep mode) μA +25°C 0.3 8 μA +85°C All devices 0.1 1.9 μA -40°C VDD = 5.0V 0.1 2.0 (Sleep mode) μA +25°C 0.4 15 μA +85°C Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. © 2009 Microchip Technology Inc. DS39632E-page 371 PIC18F2455/2550/4455/4550 Supply Current (IDD)(2) PIC18LFX455/X550 15 32 μA -40°C VDD = 2.0V FOSC = 31 kHz (RC_RUN mode, INTRC source) 15 30 μA +25°C 15 29 μA +85°C PIC18LFX455/X550 40 63 μA -40°C 35 60 μA +25°C VDD = 3.0V 30 57 μA +85°C All devices 105 168 μA -40°C 90 160 μA +25°C VDD = 5.0V 80 152 μA +85°C PIC18LFX455/X550 0.33 1 mA -40°C VDD = 2.0V FOSC = 1 MHz (RC_RUN mode, INTOSC source) 0.33 1 mA +25°C 0.33 1 mA +85°C PIC18LFX455/X550 0.6 1.3 mA -40°C 0.6 1.2 mA +25°C VDD = 3.0V 0.6 1.1 mA +85°C All devices 1.1 2.3 mA -40°C 1.1 2.2 mA +25°C VDD = 5.0V 1.0 2.1 mA +85°C PIC18LFX455/X550 0.8 2.1 mA -40°C VDD = 2.0V FOSC = 4 MHz (RC_RUN mode, INTOSC source) 0.8 2.0 mA +25°C 0.8 1.9 mA +85°C PIC18LFX455/X550 1.3 3.0 mA -40°C 1.3 3.0 mA +25°C VDD = 3.0V 1.3 3.0 mA +85°C All devices 2.5 5.3 mA -40°C 2.5 5.0 mA +25°C VDD = 5.0V 2.5 4.8 mA +85°C 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. PIC18F2455/2550/4455/4550 DS39632E-page 372 © 2009 Microchip Technology Inc. Supply Current (IDD)(2) PIC18LFX455/X550 2.9 8 μA -40°C VDD = 2.0V FOSC = 31 kHz (RC_IDLE mode, INTRC source) 3.1 8 μA +25°C 3.6 11 μA +85°C PIC18LFX455/X550 4.5 11 μA -40°C 4.8 11 μA +25°C VDD = 3.0V 5.8 15 μA +85°C All devices 9.2 16 μA -40°C 9.8 16 μA +25°C VDD = 5.0V 11.4 36 μA +85°C PIC18LFX455/X550 165 350 μA -40°C VDD = 2.0V FOSC = 1 MHz (RC_IDLE mode, INTOSC source) 175 350 μA +25°C 190 350 μA +85°C PIC18LFX455/X550 250 500 μA -40°C 270 500 μA +25°C VDD = 3.0V 290 500 μA +85°C All devices 0.50 1 mA -40°C 0.52 1 mA +25°C VDD = 5.0V 0.55 1 mA +85°C PIC18LFX455/X550 340 500 μA -40°C VDD = 2.0V FOSC = 4 MHz (RC_IDLE mode, INTOSC source) 350 500 μA +25°C 360 500 μA +85°C PIC18LFX455/X550 520 900 μA -40°C 540 900 μA +25°C VDD = 3.0V 580 900 μA +85°C All devices 1.0 1.6 mA -40°C 1.1 1.5 mA +25°C VDD = 5.0V 1.1 1.4 mA +85°C 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. © 2009 Microchip Technology Inc. DS39632E-page 373 PIC18F2455/2550/4455/4550 Supply Current (IDD)(2) PIC18LFX455/X550 250 500 μA -40°C VDD = 2.0V FOSC = 1 MHZ (PRI_RUN, EC oscillator) 250 500 μA +25°C 250 500 μA +85°C PIC18LFX455/X550 550 650 μA -40°C 480 650 μA +25°C VDD = 3.0V 460 650 μA +85°C All devices 1.2 1.6 mA -40°C 1.1 1.5 mA +25°C VDD = 5.0V 1.0 1.4 mA +85°C PIC18LFX455/X550 0.74 2.0 mA -40°C VDD = 2.0V FOSC = 4 MHz (PRI_RUN, EC oscillator) 0.74 2.0 mA +25°C 0.74 2.0 mA +85°C PIC18LFX455/X550 1.3 3.0 mA -40°C 1.3 3.0 mA +25°C VDD = 3.0V 1.3 3.0 mA +85°C All devices 2.7 6.0 mA -40°C 2.6 6.0 mA +25°C VDD = 5.0V 2.5 6.0 mA +85°C All devices 15 35 mA -40°C VDD = 4.2V FOSC = 40 MHZ (PRI_RUN, EC oscillator) 16 35 mA +25°C 16 35 mA +85°C All devices 21 40 mA -40°C 21 40 mA +25°C VDD = 5.0V 21 40 mA +85°C All devices 20 40 mA -40°C VDD = 4.2V FOSC = 48 MHZ (PRI_RUN, EC oscillator) 20 40 mA +25°C 20 40 mA +85°C All devices 25 50 mA -40°C 25 50 mA +25°C VDD = 5.0V 25 50 mA +85°C 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. PIC18F2455/2550/4455/4550 DS39632E-page 374 © 2009 Microchip Technology Inc. Supply Current (IDD)(2) PIC18LFX455/X550 65 130 μA -40°C VDD = 2.0V FOSC = 1 MHz (PRI_IDLE mode, EC oscillator) 65 120 μA +25°C 70 115 μA +85°C PIC18LFX455/X550 120 270 μA -40°C 120 250 μA +25°C VDD = 3.0V 130 240 μA +85°C All devices 230 480 μA -40°C 240 450 μA +25°C VDD = 5.0V 250 430 μA +85°C PIC18LFX455/X550 255 475 μA -40°C VDD = 2.0V FOSC = 4 MHz (PRI_IDLE mode, EC oscillator) 260 450 μA +25°C 270 430 μA +85°C PIC18LFX455/X550 420 900 μA -40°C 430 850 μA +25°C VDD = 3.0V 450 810 μA +85°C All devices 0.9 1.5 mA -40°C 0.9 1.4 mA +25°C VDD = 5.0V 0.9 1.3 mA +85°C All devices 6.0 16 mA -40°C VDD = 4.2V FOSC = 40 MHz (PRI_IDLE mode, EC oscillator) 6.2 16 mA +25°C 6.6 16 mA +85°C All devices 8.1 18 mA -40°C 8.3 18 mA +25°C VDD = 5.0V 9.0 18 mA +85°C All devices 8.0 18 mA -40°C VDD = 4.2V FOSC = 48 MHz (PRI_IDLE mode, EC oscillator) 8.1 18 mA +25°C 8.2 18 mA +85°C All devices 9.8 21 mA -40°C 10.0 21 mA +25°C VDD = 5.0V 10.5 21 mA +85°C 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. © 2009 Microchip Technology Inc. DS39632E-page 375 PIC18F2455/2550/4455/4550 Supply Current (IDD)(2) PIC18LFX455/X550 14 40 μA -40°C VDD = 2.0V FOSC = 32 kHz(3) (SEC_RUN mode, Timer1 as clock) 15 40 μA +25°C 16 40 μA +85°C PIC18LFX455/X550 40 74 μA -40°C 35 70 μA +25°C VDD = 3.0V 31 67 μA +85°C All devices 99 150 μA -40°C 81 150 μA +25°C VDD = 5.0V 75 150 μA +85°C PIC18LFX455/X550 2.5 12 μA -40°C VDD = 2.0V FOSC = 32 kHz(3) (SEC_IDLE mode, Timer1 as clock) 3.7 12 μA +25°C 4.5 12 μA +85°C PIC18LFX455/X550 5.0 15 μA -40°C 5.4 15 μA +25°C VDD = 3.0V 6.3 15 μA +85°C All devices 8.5 25 μA -40°C 9.0 25 μA +25°C VDD = 5.0V 10.5 36 μA +85°C 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. PIC18F2455/2550/4455/4550 DS39632E-page 376 © 2009 Microchip Technology Inc. Module Differential Currents (ΔIWDT, ΔIBOR, ΔILVD, ΔIOSCB, ΔIAD) D022 ΔIWDT Watchdog Timer 1.3 3.8 μA -40°C 1.4 3.8 μA +25°C VDD = 2.0V 2.0 3.8 μA +85°C 1.9 4.6 μA -40°C 2.0 4.6 μA +25°C VDD = 3.0V 2.8 4.6 μA +85°C 4.0 10 μA -40°C 5.5 10 μA +25°C VDD = 5.0V 5.6 10 μA +85°C D022A ΔIBOR Brown-out Reset(4) 35 40 μA -40°C to +85°C VDD = 3.0V 40 45 μA -40°C to +85°C VDD = 5.0V 0.1 2 μA -40°C to +85°C Sleep mode, BOREN1:BOREN0 = 10 D022B ΔILVD High/Low-Voltage Detect(4) 22 38 μA -40°C to +85°C VDD = 2.0V 25 40 μA -40°C to +85°C VDD = 3.0V 29 45 μA -40°C to +85°C VDD = 5.0V D025 ΔIOSCB Timer1 Oscillator 2.1 4.5 μA -40°C 1.8 4.5 μA +25°C VDD = 2.0V 32 kHz on Timer1(3) 2.1 4.5 μA +85°C 2.2 6.0 μA -40°C 2.6 6.0 μA +25°C VDD = 3.0V 32 kHz on Timer1(3) 2.9 6.0 μA +85°C 3.0 8.0 μA -40°C 3.2 8.0 μA +25°C VDD = 5.0V 32 kHz on Timer1(3) 3.4 8.0 μA +85°C D026 ΔIAD A/D Converter 1.0 2.0 μA -40°C to +85°C VDD = 2.0V 1.0 2.0 μA -40°C to +85°C VDD = 3.0V A/D on, not converting 1.0 2.0 μA -40°C to +85°C VDD = 5.0V 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. © 2009 Microchip Technology Inc. DS39632E-page 377 PIC18F2455/2550/4455/4550 USB and Related Module Differential Currents (ΔIUSBx, ΔIPLL, ΔIUREG) ΔIUSBx USB Module with On-Chip Transceiver 8 14.5 mA +25°C VDD = 3.0V 12.4 20 mA +25°C VDD = 5.0V ΔIPLL 96 MHz PLL (Oscillator Module) 1.2 3.0 mA +25°C VDD = 3.0V 1.2 4.8 mA +25°C VDD = 5.0V ΔIUREG USB Internal Voltage Regulator 80 125 μA +25°C VDD = 5.0V USB Idle, SUSPND (UCON<1> = 1) 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. PIC18F2455/2550/4455/4550 DS39632E-page 378 © 2009 Microchip Technology Inc. ITUSB Total USB Run Currents (ITUSB)(2) Primary Run with USB Module, PLL and USB Voltage Regulator 29 75 mA -40°C VDD = 5.0V EC+PLL 4 MHz input, 48 MHz PRI_RUN, USB module enabled in Full-Speed mode, USB VREG enabled, no bus traffic 29 65 mA +25°C VDD = 5.0V 29 65 mA +85°C VDD = 5.0V 28.2 DC Characteristics: Power-Down and Supply Current PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Device Typ Max Units Conditions Legend: Shading of rows is to assist in readability of the table. Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.). 2: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and temperature, also have an impact on the current consumption. The test conditions for all IDD measurements in active operation mode are: OSC1 = external square wave, from rail-to-rail; all I/O pins tri-stated, pulled to VDD or VSS; MCLR = VDD; WDT enabled/disabled as specified. 3: Standard low-cost 32 kHz crystals have an operating temperature range of -10°C to +70°C. Extended temperature crystals are available at a much higher cost. 4: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be less than the sum of both specifications. © 2009 Microchip Technology Inc. DS39632E-page 379 PIC18F2455/2550/4455/4550 28.3 DC Characteristics: PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) DC CHARACTERISTICS Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Characteristic Min Max Units Conditions VIL Input Low Voltage I/O Ports (except RC4/RC5 in USB mode): D030 with TTL Buffer VSS 0.15 VDD V VDD < 4.5V D030A — 0.8 V 4.5V ≤ VDD ≤ 5.5V D031 with Schmitt Trigger Buffer RB0 and RB1 VSS VSS 0.2 VDD 0.3 VDD V V When in I2C™ mode D032 MCLR VSS 0.2 VDD V D032A OSC1 and T1OSI VSS 0.3 VDD V XT, HS, HSPLL modes(1) D033 OSC1 VSS 0.2 VDD V EC mode(1) VIH Input High Voltage I/O Ports (except RC4/RC5 in USB mode): D040 with TTL Buffer 0.25 VDD + 0.8V VDD V VDD < 4.5V D040A 2.0 VDD V 4.5V ≤ VDD ≤ 5.5V D041 with Schmitt Trigger Buffer RB0 and RB1 0.8 VDD 0.7 VDD VDD VDD V V When in I2C mode D042 MCLR 0.8 VDD VDD V D042A OSC1 and T1OSI 0.7 VDD VDD V XT, HS, HSPLL modes(1) D043 OSC1 0.8 VDD VDD V EC mode(1) IIL Input Leakage Current(2) D060 I/O Ports, except D+ and D- — ±200 nA VSS ≤ VPIN ≤ VDD, Pin at high-impedance D061 MCLR — ±1 μA Vss ≤ VPIN ≤ VDD D063 OSC1 — ±1 μA Vss ≤ VPIN ≤ VDD IPU Weak Pull-up Current D070 IPURB PORTB Weak Pull-up Current 50 400 μA VDD = 5V, VPIN = VSS D071 IPURD PORTD Weak Pull-up Current 50 400 μA VDD = 5V, VPIN = VSS Note 1: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified levels represent normal operating conditions. Higher leakage current may be measured at different input voltages. 2: Negative current is defined as current sourced by the pin. 3: Parameter is characterized but not tested. PIC18F2455/2550/4455/4550 DS39632E-page 380 © 2009 Microchip Technology Inc. VOL Output Low Voltage D080 I/O Ports (except RC4/RC5 in USB mode) — 0.6 V IOL = 8.5 mA, VDD = 4.5V, -40°C to +85°C D083 OSC2/CLKO (EC, ECIO modes) — 0.6 V IOL = 1.6 mA, VDD = 4.5V, -40°C to +85°C VOH Output High Voltage(3) D090 I/O Ports (except RC4/RC5 in USB mode) VDD – 0.7 — V IOH = -3.0 mA, VDD = 4.5V, -40°C to +85°C D092 OSC2/CLKO (EC, ECIO, ECPIO modes) VDD – 0.7 — V IOH = -1.3 mA, VDD = 4.5V, -40°C to +85°C Capacitive Loading Specs on Output Pins D100 COSC2 OSC2 Pin — 15 pF In XT and HS modes when external clock is used to drive OSC1 D101 CIO All I/O Pins and OSC2 (in RC mode) — 50 pF To meet the AC Timing Specifications D102 CB SCL, SDA — 400 pF I2C™ Specification 28.3 DC Characteristics: PIC18F2455/2550/4455/4550 (Industrial) PIC18LF2455/2550/4455/4550 (Industrial) (Continued) DC CHARACTERISTICS Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Characteristic Min Max Units Conditions Note 1: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified levels represent normal operating conditions. Higher leakage current may be measured at different input voltages. 2: Negative current is defined as current sourced by the pin. 3: Parameter is characterized but not tested. © 2009 Microchip Technology Inc. DS39632E-page 381 PIC18F2455/2550/4455/4550 TABLE 28-1: MEMORY PROGRAMMING REQUIREMENTS DC Characteristics Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Sym Characteristic Min Typ† Max Units Conditions Internal Program Memory Programming Specifications(1) D110 VIHH Voltage on MCLR/VPP/RE3 pin 9.00 — 13.25 V (Note 3) D113 IDDP Supply Current during Programming — — 10 mA Data EEPROM Memory D120 ED Byte Endurance 100K 1M — E/W -40°C to +85°C D121 VDRW VDD for Read/Write VMIN — 5.5 V Using EECON to read/write VMIN = Minimum operating voltage D122 TDEW Erase/Write Cycle Time — 4 — ms D123 TRETD Characteristic Retention 40 — — Year Provided no other specifications are violated D124 TREF Number of Total Erase/Write Cycles before Refresh(2) 1M 10M — E/W -40°C to +85°C Program Flash Memory D130 EP Cell Endurance 10K 100K — E/W -40°C to +85°C D131 VPR VDD for Read VMIN — 5.5 V VMIN = Minimum operating voltage D132 VIE VDD for Bulk Erase 3.2(4) — 5.5 V Using ICSP™ port only D132A VIW VDD for All Erase/Write Operations (except bulk erase) VMIN — 5.5 V Using ICSP port or self-erase/write D133A TIW Self-Timed Write Cycle Time — 2 — ms D134 TRETD Characteristic Retention 40 100 — Year Provided no other specifications are violated † Data in “Typ” column is at 5.0V, 25°C unless otherwise stated. These parameters are for design guidance only and are not tested. Note 1: These specifications are for programming the on-chip program memory through the use of table write instructions. 2: Refer to Section 7.7 “Using the Data EEPROM” for a more detailed discussion on data EEPROM endurance. 3: Required only if Single-Supply Programming is disabled. 4: Minimum voltage is 3.2V for PIC18LF devices in the family. Minimum voltage is 4.2V for PIC18F devices in the family. PIC18F2455/2550/4455/4550 DS39632E-page 382 © 2009 Microchip Technology Inc. TABLE 28-2: COMPARATOR SPECIFICATIONS TABLE 28-3: VOLTAGE REFERENCE SPECIFICATIONS Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C (unless otherwise stated) Param No. Sym Characteristics Min Typ Max Units Comments D300 VIOFF Input Offset Voltage — ±5.0 ±10 mV D301 VICM Input Common Mode Voltage 0 — VDD – 1.5 V D302 CMRR Common Mode Rejection Ratio 55 — — dB 300 TRESP Response Time(1) — 150 400 ns PIC18FXXXX 300A — 150 600 ns PIC18LFXXXX, VDD = 2.0V 301 TMC2OV Comparator Mode Change to Output Valid — — 10 μs Note 1: Response time measured with one comparator input at (VDD – 1.5)/2, while the other input transitions from VSS to VDD. Operating Conditions: 3.0V < VDD < 5.5V, -40°C < TA < +85°C (unless otherwise stated) Param No. Sym Characteristics Min Typ Max Units Comments D310 VRES Resolution VDD/24 — VDD/32 LSb D311 VRAA Absolute Accuracy — — 1/4 — 1 1/2 LSb LSb Low Range (CVRR = 1) High Range (CVRR = 0) D312 VRUR Unit Resistor Value (R) — 2k — Ω 310 TSET Settling Time(1) — — 10 μs Note 1: Settling time measured while CVRR = 1 and CVR3:CVR0 transitions from ‘0000’ to ‘1111’. © 2009 Microchip Technology Inc. DS39632E-page 383 PIC18F2455/2550/4455/4550 TABLE 28-4: USB MODULE SPECIFICATIONS TABLE 28-5: USB INTERNAL VOLTAGE REGULATOR SPECIFICATIONS Operating Conditions: -40°C < TA < +85°C (unless otherwise stated). Param No. Sym Characteristic Min Typ Max Units Comments D313 VUSB USB Voltage 3.0 — 3.6 V Voltage on pin must be in this range for proper USB operation D314 IIL Input Leakage on D+ and Dpins — — ±1 μA VSS ≤ VPIN ≤ VDD; pin at high-impedance D315 VILUSB Input Low Voltage for USB Buffer — — 0.8 V For VUSB range D316 VIHUSB Input High Voltage for USB Buffer 2.0 — — V For VUSB range D317 VCRS Crossover Voltage 1.3 2.0 V Voltage range for D+ and Dcrossover to occur D318 VDIFS Differential Input Sensitivity — — 0.2 V The difference between D+ and D- must exceed this value while VCM is met D319 VCM Differential Common Mode Range 0.8 — 2.5 V D320 ZOUT Driver Output Impedance 28 — 44 Ω D321 VOL Voltage Output Low 0.0 — 0.3 V 1.5 kΩ load connected to 3.6V D322 VOH Voltage Output High 2.8 — 3.6 V 15 kΩ load connected to ground Operating Conditions: -40°C < TA < +85°C (unless otherwise stated). Param No. Sym Characteristics Min Typ Max Units Comments D323 VUSBANA Regulator Output Voltage 3.0 — 3.6 V VDD > 4.0V(1) D324 CUSB External Filter Capacitor Value (VUSB to VSS) 0.22 0.47 12(2) μF Ceramic or other low-ESR capacitor recommended Note 1: If device VDD is less than 4.0V, the internal USB voltage regulator should be disabled and an external 3.0-3.6V supply should be provided on VUSB if the USB module is used. 2: This is a recommended maximum for start-up time and in-rush considerations. When the USB regulator is disabled, there is no maximum. PIC18F2455/2550/4455/4550 DS39632E-page 384 © 2009 Microchip Technology Inc. FIGURE 28-3: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS TABLE 28-6: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS VHLVD HLVDIF VDD (HLVDIF set by hardware) (HLVDIF can be cleared in software) VHLVD For VDIRMAG = 1: For VDIRMAG = 0: VDD Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Symbol Characteristic Min Typ Max Units Conditions D420 HLVD Voltage on VDD Transition High-to-Low HLVDL<3:0> = 0000 2.06 2.17 2.28 V HLVDL<3:0> = 0001 2.12 2.23 2.34 V HLVDL<3:0> = 0010 2.24 2.36 2.48 V HLVDL<3:0> = 0011 2.32 2.44 2.56 V HLVDL<3:0> = 0100 2.47 2.60 2.73 V HLVDL<3:0> = 0101 2.65 2.79 2.93 V HLVDL<3:0> = 0110 2.74 2.89 3.04 V HLVDL<3:0> = 0111 2.96 3.12 3.28 V HLVDL<3:0> = 1000 3.22 3.39 3.56 V HLVDL<3:0> = 1001 3.37 3.55 3.73 V HLVDL<3:0> = 1010 3.52 3.71 3.90 V HLVDL<3:0> = 1011 3.70 3.90 4.10 V HLVDL<3:0> = 1100 3.90 4.11 4.32 V HLVDL<3:0> = 1101 4.11 4.33 4.55 V HLVDL<3:0> = 1110 4.36 4.59 4.82 V HLVDL<3:0> = 1111 1.14 1.20 1.26 V Voltage at HLVDIN input pin compared to Internal Voltage Reference © 2009 Microchip Technology Inc. DS39632E-page 385 PIC18F2455/2550/4455/4550 28.4 AC (Timing) Characteristics 28.4.1 TIMING PARAMETER SYMBOLOGY The timing parameter symbols have been created using one of the following formats: 1. TppS2ppS 3. TCC:ST (I2C specifications only) 2. TppS 4. Ts (I2C specifications only) T F Frequency T Time Lowercase letters (pp) and their meanings: pp ad SPP address write mc MCLR cc CCP1 osc OSC1 ck CLKO rd RD cs CS rw RD or WR da SPP data write sc SCK di SDI ss SS do SDO t0 T0CKI dt Data in t1 T13CKI io I/O port wr WR Uppercase letters and their meanings: S F Fall P Period H High R Rise I Invalid (High-Impedance) V Valid L Low Z High-Impedance I2C only AA output access High High BUF Bus free Low Low TCC:ST (I2C specifications only) CC HD Hold SU Setup ST DAT DATA input hold STO Stop condition STA Start condition PIC18F2455/2550/4455/4550 DS39632E-page 386 © 2009 Microchip Technology Inc. 28.4.2 TIMING CONDITIONS The temperature and voltages specified in Table 28-7 apply to all timing specifications unless otherwise noted. Figure 28-4 specifies the load conditions for the timing specifications. TABLE 28-7: TEMPERATURE AND VOLTAGE SPECIFICATIONS – AC FIGURE 28-4: LOAD CONDITIONS FOR DEVICE TIMING SPECIFICATIONS Note: Because of space limitations, the generic terms “PIC18FXXXX” and “PIC18LFXXXX” are used throughout this section to refer to the PIC18F2455/2550/4455/4550 and PIC18LF2455/2550/4455/4550 families of devices specifically and only those devices. AC CHARACTERISTICS Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Operating voltage VDD range as described in DC spec Section 28.1 and Section 28.3. LF parts operate for industrial temperatures only. VDD/2 CL RL Pin Pin VSS VSS CL RL = 464Ω CL = 50 pF for all pins except OSC2/CLKO and including D and E outputs as ports Load Condition 1 Load Condition 2 © 2009 Microchip Technology Inc. DS39632E-page 387 PIC18F2455/2550/4455/4550 28.4.3 TIMING DIAGRAMS AND SPECIFICATIONS FIGURE 28-5: EXTERNAL CLOCK TIMING (ALL MODES EXCEPT PLL) TABLE 28-8: EXTERNAL CLOCK TIMING REQUIREMENTS OSC1 CLKO Q4 Q1 Q2 Q3 Q4 Q1 1 2 3 3 4 4 Param. No. Symbol Characteristic Min Max Units Conditions 1A FOSC External CLKI Frequency(1) Oscillator Frequency(1) DC 48 MHz EC, ECIO Oscillator mode 0.2 1 MHz XT, XTPLL Oscillator mode 4 25(2) MHz HS Oscillator mode 4 24(2) MHz HSPLL Oscillator mode 1 TOSC External CLKI Period(1) Oscillator Period(1) 20.8 DC ns EC, ECIO Oscillator mode 1000 5000 ns XT Oscillator mode 40 40 250 250 ns ns HS Oscillator mode HSPLL Oscillator mode 2 TCY Instruction Cycle Time(1) 83.3 DC ns TCY = 4/FOSC 3 TosL, TosH External Clock in (OSC1) High or Low Time 30 — ns XT Oscillator mode 10 — ns HS Oscillator mode 4 TosR, TosF External Clock in (OSC1) Rise or Fall Time — 20 ns XT Oscillator mode — 7.5 ns HS Oscillator mode Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period for all configurations except PLL. All specified values are based on characterization data for that particular oscillator type under standard operating conditions with the device executing code. Exceeding these specified limits may result in an unstable oscillator operation and/or higher than expected current consumption. All devices are tested to operate at “min.” values with an external clock applied to the OSC1/CLKI pin. When an external clock input is used, the “max.” cycle time limit is “DC” (no clock) for all devices. 2: When VDD >= 3.3V, the maximum crystal or resonator frequency is 25 MHz (or 24 MHz with PLL prescaler). When 2.0V < VDD < 3.3V, the maximum crystal frequency = (16.36 MHz/V)(VDD – 2.0V) + 4 MHz. PIC18F2455/2550/4455/4550 DS39632E-page 388 © 2009 Microchip Technology Inc. TABLE 28-9: PLL CLOCK TIMING SPECIFICATIONS (VDD = 3.0V TO 5.5V) TABLE 28-10: AC CHARACTERISTICS: INTERNAL RC ACCURACY PIC18F2455/2550/4455/4550 (INDUSTRIAL) PIC18LF2455/2550/4455/4550 (INDUSTRIAL) Param No. Sym Characteristic Min Typ† Max Units Conditions F10 FOSC Oscillator Frequency Range 4 — 48 MHz With PLL prescaler F11 FSYS On-Chip VCO System Frequency — 96 — MHz F12 trc PLL Start-up Time (Lock Time) — — 2 ms F13 ΔCLK CLKO Stability (Jitter) -0.25 — +0.25 % † Data in “Typ” column is at 5V, 25°C unless otherwise stated. These parameters are for design guidance only and are not tested. PIC18LF2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial PIC18F2455/2550/4455/4550 (Industrial) Standard Operating Conditions (unless otherwise stated) Operating temperature -40°C ≤ TA ≤ +85°C for industrial Param No. Device Min Typ Max Units Conditions INTOSC Accuracy @ Freq = 8 MHz, 4 MHz, 2 MHz, 1 MHz, 500 kHz, 250 kHz, 125 kHz(1) F14 PIC18LF2455/2550/4455/4550 -2 +/-1 2 % +25°C VDD = 2.7-3.3V F15 -5 — 5 % -10°C to +85°C VDD = 2.7-3.3V F16 -10 +/-1 10 % -40°C to +85°C VDD = 2.7-3.3V F17 PIC18F2455/2550/4455/4550 -2 +/-1 2 % +25°C VDD = 4.5-5.5V F18 -5 — 5 % -10°C to +85°C VDD = 4.5-5.5V F19 -10 +/-1 10 % -40°C to +85°C VDD = 4.5-5.5V INTRC Accuracy @ Freq = 31 kHz(2) F20 PIC18LF2455/2550/4455/4550 26.562 — 35.938 kHz -40°C to +85°C VDD = 2.7-3.3V F21 PIC18F2455/2550/4455/4550 26.562 — 35.938 kHz -40°C to +85°C VDD = 4.5-5.5V Legend: Shading of rows is to assist in readability of the table. Note 1: Frequency calibrated at 25°C. OSCTUNE register can be used to compensate for temperature drift. 2: INTRC frequency after calibration. 3: Change of INTRC frequency as VDD changes. © 2009 Microchip Technology Inc. DS39632E-page 389 PIC18F2455/2550/4455/4550 FIGURE 28-6: CLKO AND I/O TIMING TABLE 28-11: CLKO AND I/O TIMING REQUIREMENTS Note: Refer to Figure 28-4 for load conditions. OSC1 CLKO I/O pin (Input) I/O pin (Output) Q4 Q1 Q2 Q3 10 13 14 17 20, 21 19 18 15 11 12 16 Old Value New Value Param No. Symbol Characteristic Min Typ Max Units Conditions 10 TosH2ckL OSC1 ↑ to CLKO ↓ — 75 200 ns (Note 1) 11 TosH2ckH OSC1 ↑ to CLKO ↑ — 75 200 ns (Note 1) 12 TckR CLKO Rise Time — 35 100 ns (Note 1) 13 TckF CLKO Fall Time — 35 100 ns (Note 1) 14 TckL2ioV CLKO ↓ to Port Out Valid — — 0.5 TCY + 20 ns (Note 1) 15 TioV2ckH Port In Valid before CLKO ↑ 0.25 TCY + 25 — — ns (Note 1) 16 TckH2ioI Port In Hold after CLKO ↑ 0 — — ns (Note 1) 17 TosH2ioV OSC1 ↑ (Q1 cycle) to Port Out Valid — 50 150 ns 18 TosH2ioI OSC1 ↑ (Q2 cycle) to Port Input Invalid (I/O in hold time) PIC18FXXXX 100 — — ns 18A PIC18LFXXXX 200 — — ns VDD = 2.0V 19 TioV2osH Port Input Valid to OSC1 ↑ (I/O in setup time) 0 — — ns 20 TioR Port Output Rise Time PIC18FXXXX — 10 25 ns 20A PIC18LFXXXX — — 60 ns VDD = 2.0V 21 TioF Port Output Fall Time PIC18FXXXX — 10 25 ns 21A PIC18LFXXXX — — 60 ns VDD = 2.0V 22† TINP INTx pin High or Low Time TCY — — ns 23† TRBP RB7:RB4 Change INTx High or Low Time TCY — — ns † These parameters are asynchronous events not related to any internal clock edges. Note 1: Measurements are taken in RC mode, where CLKO output is 4 x TOSC. PIC18F2455/2550/4455/4550 DS39632E-page 390 © 2009 Microchip Technology Inc. FIGURE 28-7: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND POWER-UP TIMER TIMING FIGURE 28-8: BROWN-OUT RESET TIMING TABLE 28-12: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER AND BROWN-OUT RESET REQUIREMENTS Param. No. Symbol Characteristic Min Typ Max Units Conditions 30 TmcL MCLR Pulse Width (low) 2 — — μs 31 TWDT Watchdog Timer Time-out Period (no postscaler) 3.5 4.1 4.8 ms 32 TOST Oscillator Start-up Timer Period 1024 TOSC — 1024 TOSC — TOSC = OSC1 period 33 TPWRT Power-up Timer Period 57.0 65.5 77.1 ms 34 TIOZ I/O High-Impedance from MCLR Low or Watchdog Timer Reset — 2 — μs 35 TBOR Brown-out Reset Pulse Width 200 — — μs VDD ≤ BVDD (see D005) 36 TIRVST Time for Internal Reference Voltage to become Stable — 20 50 μs 37 TLVD Low-Voltage Detect Pulse Width 200 — — μs VDD ≤ VLVD 38 TCSD CPU Start-up Time 5 — 10 μs 39 TIOBST Time for INTOSC to Stabilize — 1 — ms VDD MCLR Internal POR PWRT Time-out Oscillator Time-out Internal Reset Watchdog Timer Reset 33 32 30 31 34 I/O pins 34 Note: Refer to Figure 28-4 for load conditions. VDD BVDD 35 VBGAP = 1.2V VIRVST Enable Internal Internal Reference 36 Reference Voltage Voltage Stable © 2009 Microchip Technology Inc. DS39632E-page 391 PIC18F2455/2550/4455/4550 FIGURE 28-9: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS TABLE 28-13: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS Note: Refer to Figure 28-4 for load conditions. 46 47 45 48 41 42 40 T0CKI T1OSO/T13CKI TMR0 or TMR1 Param No. Symbol Characteristic Min Max Units Conditions 40 Tt0H T0CKI High Pulse Width No prescaler 0.5 TCY + 20 — ns With prescaler 10 — ns 41 Tt0L T0CKI Low Pulse Width No prescaler 0.5 TCY + 20 — ns With prescaler 10 — ns 42 Tt0P T0CKI Period No prescaler TCY + 10 — ns With prescaler Greater of: 20 ns or (TCY + 40)/N — ns N = prescale value (1, 2, 4,..., 256) 45 Tt1H T13CKI High Time Synchronous, no prescaler 0.5 TCY + 20 — ns Synchronous, with prescaler PIC18FXXXX 10 — ns PIC18LFXXXX 25 — ns VDD = 2.0V Asynchronous PIC18FXXXX 30 — ns PIC18LFXXXX 50 — ns VDD = 2.0V 46 Tt1L T13CKI Low Time Synchronous, no prescaler 0.5 TCY + 5 — ns Synchronous, with prescaler PIC18FXXXX 10 — ns PIC18LFXXXX 25 — ns VDD = 2.0V Asynchronous PIC18FXXXX 30 — ns PIC18LFXXXX 50 — ns VDD = 2.0V 47 Tt1P T13CKI Input Period Synchronous Greater of: 20 ns or (TCY + 40)/N — ns N = prescale value (1, 2, 4, 8) Asynchronous 60 — ns Ft1 T13CKI Oscillator Input Frequency Range DC 50 kHz 48 Tcke2tmrI Delay from External T13CKI Clock Edge to Timer Increment 2 TOSC 7 TOSC — PIC18F2455/2550/4455/4550 DS39632E-page 392 © 2009 Microchip Technology Inc. FIGURE 28-10: CAPTURE/COMPARE/PWM TIMINGS (ALL CCP MODULES) TABLE 28-14: CAPTURE/COMPARE/PWM REQUIREMENTS (ALL CCP MODULES) Note: Refer to Figure 28-4 for load conditions. CCPx (Capture Mode) 50 51 52 CCPx 53 54 (Compare or PWM Mode) Param No. Symbol Characteristic Min Max Units Conditions 50 TccL CCPx Input Low Time No prescaler 0.5 TCY + 20 — ns With prescaler PIC18FXXXX 10 — ns PIC18LFXXXX 20 — ns VDD = 2.0V 51 TccH CCPx Input High Time No prescaler 0.5 TCY + 20 — ns With prescaler PIC18FXXXX 10 — ns PIC18LFXXXX 20 — ns VDD = 2.0V 52 TccP CCPx Input Period 3 TCY + 40 N — ns N = prescale value (1, 4 or 16) 53 TccR CCPx Output Fall Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 54 TccF CCPx Output Fall Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V © 2009 Microchip Technology Inc. DS39632E-page 393 PIC18F2455/2550/4455/4550 FIGURE 28-11: EXAMPLE SPI MASTER MODE TIMING (CKE = 0) TABLE 28-15: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 0) SS SCK (CKP = 0) SCK (CKP = 1) SDO SDI 70 71 72 73 74 75, 76 80 79 78 78 79 MSb bit 6 - - - - - -1 LSb bit 6 - - - -1 LSb In Note: Refer to Figure 28-4 for load conditions. MSb In Param No. Symbol Characteristic Min Max Units Conditions 70 TssL2scH, TssL2scL SS ↓ to SCK ↓ or SCK ↑ Input 3 TCY — ns 71 TscH SCK Input High Time (Slave mode) Continuous 1.25 TCY + 30 — ns 71A Single Byte 40 — ns (Note 1) 72 TscL SCK Input Low Time (Slave mode) Continuous 1.25 TCY + 30 — ns 72A Single Byte 40 — ns (Note 1) 73 TdiV2scH, TdiV2scL Setup Time of SDI Data Input to SCK Edge 20 — ns 73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2) 74 TscH2diL, TscL2diL Hold Time of SDI Data Input to SCK Edge 35 — ns 75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 76 TdoF SDO Data Output Fall Time — 25 ns 78 TscR SCK Output Rise Time (Master mode) PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 79 TscF SCK Output Fall Time (Master mode) — 25 ns 80 TscH2doV, TscL2doV SDO Data Output Valid after SCK Edge PIC18FXXXX — 50 ns PIC18LFXXXX — 100 ns VDD = 2.0V Note 1: Requires the use of Parameter 73A. 2: Only if Parameter 71A and 72A are used. PIC18F2455/2550/4455/4550 DS39632E-page 394 © 2009 Microchip Technology Inc. FIGURE 28-12: EXAMPLE SPI MASTER MODE TIMING (CKE = 1) TABLE 28-16: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 1) Param. No. Symbol Characteristic Min Max Units Conditions 71 TscH SCK Input High Time (Slave mode) Continuous 1.25 TCY + 30 — ns 71A Single Byte 40 — ns (Note 1) 72 TscL SCK Input Low Time (Slave mode) Continuous 1.25 TCY + 30 — ns 72A Single Byte 40 — ns (Note 1) 73 TdiV2scH, TdiV2scL Setup Time of SDI Data Input to SCK Edge 20 — ns 73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2) 74 TscH2diL, TscL2diL Hold Time of SDI Data Input to SCK Edge 35 — ns 75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 76 TdoF SDO Data Output Fall Time — 25 ns 78 TscR SCK Output Rise Time (Master mode) PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 79 TscF SCK Output Fall Time (Master mode) — 25 ns 80 TscH2doV, TscL2doV SDO Data Output Valid after SCK Edge PIC18FXXXX — 50 ns PIC18LFXXXX — 100 ns VDD = 2.0V 81 TdoV2scH, TdoV2scL SDO Data Output Setup to SCK Edge TCY — ns Note 1: Requires the use of Parameter 73A. 2: Only if Parameter 71A and 72A are used. SS SCK (CKP = 0) SCK (CKP = 1) SDO SDI 81 71 72 74 75, 76 78 80 MSb 79 73 MSb In bit 6 - - - - - -1 bit 6 - - - -1 LSb In LSb Note: Refer to Figure 28-4 for load conditions. © 2009 Microchip Technology Inc. DS39632E-page 395 PIC18F2455/2550/4455/4550 FIGURE 28-13: EXAMPLE SPI SLAVE MODE TIMING (CKE = 0) TABLE 28-17: EXAMPLE SPI MODE REQUIREMENTS (SLAVE MODE TIMING, CKE = 0) Param No. Symbol Characteristic Min Max Units Conditions 70 TssL2scH, TssL2scL SS ↓ to SCK ↓ or SCK ↑ Input 3 TCY — ns 71 TscH SCK Input High Time (Slave mode) Continuous 1.25 TCY + 30 — ns 71A Single Byte 40 — ns (Note 1) 72 TscL SCK Input Low Time (Slave mode) Continuous 1.25 TCY + 30 — ns 72A Single Byte 40 — ns (Note 1) 73 TdiV2scH, TdiV2scL Setup Time of SDI Data Input to SCK Edge 20 — ns 73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2) 74 TscH2diL, TscL2diL Hold Time of SDI Data Input to SCK Edge 35 — ns 75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 76 TdoF SDO Data Output Fall Time — 25 ns 77 TssH2doZ SS ↑ to SDO Output High-Impedance 10 50 ns 78 TscR SCK Output Rise Time (Master mode) PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 79 TscF SCK Output Fall Time (Master mode) — 25 ns 80 TscH2doV, TscL2doV SDO Data Output Valid after SCK Edge PIC18FXXXX — 50 ns PIC18LFXXXX — 100 ns VDD = 2.0V 83 TscH2ssH, TscL2ssH SS ↑ after SCK edge 1.5 TCY + 40 — ns Note 1: Requires the use of Parameter 73A. 2: Only if Parameter 71A and 72A are used. SS SCK (CKP = 0) SCK (CKP = 1) SDO 70 71 72 73 74 75, 76 77 80 79 78 78 79 SDI MSb bit 6 - - - - - -1 LSb MSb In bit 6 - - - -1 LSb In 83 Note: Refer to Figure 28-4 for load conditions. PIC18F2455/2550/4455/4550 DS39632E-page 396 © 2009 Microchip Technology Inc. FIGURE 28-14: EXAMPLE SPI SLAVE MODE TIMING (CKE = 1) TABLE 28-18: EXAMPLE SPI SLAVE MODE REQUIREMENTS (CKE = 1) Param No. Symbol Characteristic Min Max Units Conditions 70 TssL2scH, TssL2scL SS ↓ to SCK ↓ or SCK ↑ Input 3 TCY — ns 71 TscH SCK Input High Time (Slave mode) Continuous 1.25 TCY + 30 — ns 71A Single Byte 40 — ns (Note 1) 72 TscL SCK Input Low Time (Slave mode) Continuous 1.25 TCY + 30 — ns 72A Single Byte 40 — ns (Note 1) 73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2) 74 TscH2diL, TscL2diL Hold Time of SDI Data Input to SCK Edge 35 — ns 75 TdoR SDO Data Output Rise Time PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 76 TdoF SDO Data Output Fall Time — 25 ns 77 TssH2doZ SS ↑ to SDO Output High-Impedance 10 50 ns 78 TscR SCK Output Rise Time (Master mode) PIC18FXXXX — 25 ns PIC18LFXXXX — 45 ns VDD = 2.0V 79 TscF SCK Output Fall Time (Master mode) — 25 ns 80 TscH2doV, TscL2doV SDO Data Output Valid after SCK Edge PIC18FXXXX — 50 ns PIC18LFXXXX — 100 ns VDD = 2.0V 82 TssL2doV SDO Data Output Valid after SS ↓ Edge PIC18FXXXX — 50 ns PIC18LFXXXX — 100 ns VDD = 2.0V 83 TscH2ssH, TscL2ssH SS ↑ after SCK Edge 1.5 TCY + 40 — ns Note 1: Requires the use of Parameter 73A. 2: Only if Parameter 71A and 72A are used. SS SCK (CKP = 0) SCK (CKP = 1) SDO 70 71 72 82 SDI 74 75, 76 MSb bit 6 - - - - - -1 LSb 77 MSb In bit 6 - - - -1 LSb In 80 83 Note: Refer to Figure 28-4 for load conditions. © 2009 Microchip Technology Inc. DS39632E-page 397 PIC18F2455/2550/4455/4550 FIGURE 28-15: I2C™ BUS START/STOP BITS TIMING TABLE 28-19: I2C™ BUS START/STOP BITS REQUIREMENTS (SLAVE MODE) FIGURE 28-16: I2C™ BUS DATA TIMING Note: Refer to Figure 28-4 for load conditions. 91 92 93 SCL SDA Start Condition Stop Condition 90 Param. No. Symbol Characteristic Min Max Units Conditions 90 TSU:STA Start Condition 100 kHz mode 4700 — ns Only relevant for Repeated Setup Time 400 kHz mode 600 — Start condition 91 THD:STA Start Condition 100 kHz mode 4000 — ns After this period, the first Hold Time 400 kHz mode 600 — clock pulse is generated 92 TSU:STO Stop Condition 100 kHz mode 4700 — ns Setup Time 400 kHz mode 600 — 93 THD:STO Stop Condition 100 kHz mode 4000 — ns Hold Time 400 kHz mode 600 — Note: Refer to Figure 28-4 for load conditions. 90 91 92 100 101 103 106 109 109 110 102 SCL SDA In SDA Out 107 PIC18F2455/2550/4455/4550 DS39632E-page 398 © 2009 Microchip Technology Inc. TABLE 28-20: I2C™ BUS DATA REQUIREMENTS (SLAVE MODE) Param. No. Symbol Characteristic Min Max Units Conditions 100 THIGH Clock High Time 100 kHz mode 4.0 — μs PIC18FXXXX must operate at a minimum of 1.5 MHz 400 kHz mode 0.6 — μs PIC18FXXXX must operate at a minimum of 10 MHz MSSP Module 1.5 TCY — 101 TLOW Clock Low Time 100 kHz mode 4.7 — μs PIC18FXXXX must operate at a minimum of 1.5 MHz 400 kHz mode 1.3 — μs PIC18FXXXX must operate at a minimum of 10 MHz MSSP Module 1.5 TCY — 102 TR SDA and SCL Rise Time 100 kHz mode — 1000 ns 400 kHz mode 20 + 0.1 CB 300 ns CB is specified to be from 10 to 400 pF 103 TF SDA and SCL Fall Time 100 kHz mode — 300 ns 400 kHz mode 20 + 0.1 CB 300 ns CB is specified to be from 10 to 400 pF 90 TSU:STA Start Condition Setup Time 100 kHz mode 4.7 — μs Only relevant for Repeated 400 kHz mode 0.6 — μs Start condition 91 THD:STA Start Condition Hold Time 100 kHz mode 4.0 — μs After this period, the first 400 kHz mode 0.6 — μs clock pulse is generated 106 THD:DAT Data Input Hold Time 100 kHz mode 0 — ns 400 kHz mode 0 0.9 μs 107 TSU:DAT Data Input Setup Time 100 kHz mode 250 — ns (Note 2) 400 kHz mode 100 — ns 92 TSU:STO Stop Condition Setup Time 100 kHz mode 4.7 — μs 400 kHz mode 0.6 — μs 109 TAA Output Valid from Clock 100 kHz mode — 3500 ns (Note 1) 400 kHz mode — — ns 110 TBUF Bus Free Time 100 kHz mode 4.7 — μs Time the bus must be free before a new transmission can start 400 kHz mode 1.3 — μs D102 CB Bus Capacitive Loading — 400 pF Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region (min. 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions. 2: A Fast mode I2C™ bus device can be used in a Standard mode I2C bus system but the requirement, TSU:DAT ≥ 250 ns, must then be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit to the SDA line, TR max. + TSU:DAT = 1000 + 250 = 1250 ns (according to the Standard mode I2C bus specification), before the SCL line is released. © 2009 Microchip Technology Inc. DS39632E-page 399 PIC18F2455/2550/4455/4550 FIGURE 28-17: MASTER SSP I2C™ BUS START/STOP BITS TIMING WAVEFORMS TABLE 28-21: MASTER SSP I2C™ BUS START/STOP BITS REQUIREMENTS FIGURE 28-18: MASTER SSP I2C™ BUS DATA TIMING Note: Refer to Figure 28-4 for load conditions. 91 93 SCL SDA Start Condition Stop Condition 90 92 Param. No. Symbol Characteristic Min Max Units Conditions 90 TSU:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns Only relevant for Repeated Start condition Setup Time 400 kHz mode 2(TOSC)(BRG + 1) — 1 MHz mode(1) 2(TOSC)(BRG + 1) — 91 THD:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns After this period, the first clock pulse is generated Hold Time 400 kHz mode 2(TOSC)(BRG + 1) — 1 MHz mode(1) 2(TOSC)(BRG + 1) — 92 TSU:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns Setup Time 400 kHz mode 2(TOSC)(BRG + 1) — 1 MHz mode(1) 2(TOSC)(BRG + 1) — 93 THD:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns Hold Time 400 kHz mode 2(TOSC)(BRG + 1) — 1 MHz mode(1) 2(TOSC)(BRG + 1) — Note 1: Maximum pin capacitance = 10 pF for all I2C™ pins. Note: Refer to Figure 28-4 for load conditions. 90 91 92 100 101 103 106 107 109 109 110 102 SCL SDA In SDA Out PIC18F2455/2550/4455/4550 DS39632E-page 400 © 2009 Microchip Technology Inc. TABLE 28-22: MASTER SSP I2C™ BUS DATA REQUIREMENTS Param. No. Symbol Characteristic Min Max Units Conditions 100 THIGH Clock High Time 100 kHz mode 2(TOSC)(BRG + 1) — ms 400 kHz mode 2(TOSC)(BRG + 1) — ms 1 MHz mode(1) 2(TOSC)(BRG + 1) — ms 101 TLOW Clock Low Time 100 kHz mode 2(TOSC)(BRG + 1) — ms 400 kHz mode 2(TOSC)(BRG + 1) — ms 1 MHz mode(1) 2(TOSC)(BRG + 1) — ms 102 TR SDA and SCL Rise Time 100 kHz mode — 1000 ns CB is specified to be from 400 kHz mode 20 + 0.1 CB 300 ns 10 to 400 pF 1 MHz mode(1) — 300 ns 103 TF SDA and SCL Fall Time 100 kHz mode — 300 ns CB is specified to be from 400 kHz mode 20 + 0.1 CB 300 ns 10 to 400 pF 1 MHz mode(1) — 100 ns 90 TSU:STA Start Condition Setup Time 100 kHz mode 2(TOSC)(BRG + 1) — ms Only relevant for Repeated Start condition 400 kHz mode 2(TOSC)(BRG + 1) — ms 1 MHz mode(1) 2(TOSC)(BRG + 1) — ms 91 THD:STA Start Condition Hold Time 100 kHz mode 2(TOSC)(BRG + 1) — ms After this period, the first 400 kHz mode 2(TOSC)(BRG + 1) — ms clock pulse is generated 1 MHz mode(1) 2(TOSC)(BRG + 1) — ms 106 THD:DAT Data Input Hold Time 100 kHz mode 0 — ns 400 kHz mode 0 0.9 ms 107 TSU:DAT Data Input Setup Time 100 kHz mode 250 — ns (Note 2) 400 kHz mode 100 — ns 92 TSU:STO Stop Condition Setup Time 100 kHz mode 2(TOSC)(BRG + 1) — ms 400 kHz mode 2(TOSC)(BRG + 1) — ms 1 MHz mode(1) 2(TOSC)(BRG + 1) — ms 109 TAA Output Valid from Clock 100 kHz mode — 3500 ns 400 kHz mode — 1000 ns 1 MHz mode(1) — — ns 110 TBUF Bus Free Time 100 kHz mode 4.7 — ms Time the bus must be free before a new transmission can start 400 kHz mode 1.3 — ms D102 CB Bus Capacitive Loading — 400 pF Note 1: Maximum pin capacitance = 10 pF for all I2C™ pins. 2: A Fast mode I2C bus device can be used in a Standard mode I2C bus system but parameter #107 ≥ 250 ns must then be met. This will automatically be the case if the device does not stretch the LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit to the SDA line, parameter #102 + parameter #107 = 1000 + 250 = 1250 ns (for 100 kHz mode), before the SCL line is released. © 2009 Microchip Technology Inc. DS39632E-page 401 PIC18F2455/2550/4455/4550 FIGURE 28-19: EUSART SYNCHRONOUS TRANSMISSION (MASTER/SLAVE) TIMING TABLE 28-23: EUSART SYNCHRONOUS TRANSMISSION REQUIREMENTS FIGURE 28-20: EUSART SYNCHRONOUS RECEIVE (MASTER/SLAVE) TIMING TABLE 28-24: EUSART SYNCHRONOUS RECEIVE REQUIREMENTS 121 121 120 122 RC6/TX/CK RC7/RX/DT/SDO pin pin Note: Refer to Figure 28-4 for load conditions. Param No. Symbol Characteristic Min Max Units Conditions 120 TckH2dtV SYNC XMIT (MASTER & SLAVE) Clock High to Data Out Valid PIC18FXXXX — 40 ns PIC18LFXXXX — 100 ns VDD = 2.0V 121 Tckrf Clock Out Rise Time and Fall Time (Master mode) PIC18FXXXX — 20 ns PIC18LFXXXX — 50 ns VDD = 2.0V 122 Tdtrf Data Out Rise Time and Fall Time PIC18FXXXX — 20 ns PIC18LFXXXX — 50 ns VDD = 2.0V 125 126 RC6/TX/CK RC7/RX/DT/SDO pin pin Note: Refer to Figure 28-4 for load conditions. Param. No. Symbol Characteristic Min Max Units Conditions 125 TDTV2CKL SYNC RCV (MASTER & SLAVE) Data Hold before CK ↓ (DT hold time) 10 — ns 126 TCKL2DTL Data Hold after CK ↓ (DT hold time) 15 — ns PIC18F2455/2550/4455/4550 DS39632E-page 402 © 2009 Microchip Technology Inc. FIGURE 28-21: USB SIGNAL TIMING TABLE 28-25: USB LOW-SPEED TIMING REQUIREMENTS TABLE 28-26: USB FULL-SPEED REQUIREMENTS VCRS USB Data Differential Lines 90% 10% TLR, TFR TLF, TFF Param No. Symbol Characteristic Min Typ Max Units Conditions T01 TLR Transition Rise Time 75 — 300 ns CL = 200 to 600 pF T02 TLF Transition Fall Time 75 — 300 ns CL = 200 to 600 pF T03 TLRFM Rise/Fall Time Matching 80 — 125 % Param No. Symbol Characteristic Min Typ Max Units Conditions T04 TFR Transition Rise Time 4 — 20 ns CL = 50 pF T05 TFF Transition Fall Time 4 — 20 ns CL = 50 pF T06 TFRFM Rise/Fall Time Matching 90 — 111.1 % © 2009 Microchip Technology Inc. DS39632E-page 403 PIC18F2455/2550/4455/4550 FIGURE 28-22: STREAMING PARALLEL PORT TIMING (PIC18F4455/4550) TABLE 28-27: STREAMING PARALLEL PORT REQUIREMENTS (PIC18F4455/4550) OESPP CSSPP SPP<7:0> Write Data ToeF2adR ToeF2adV ToeR2adI ToeF2daR ToeF2daV ToeR2adI Note: Refer to Figure 28-4 for load conditions. Write Address Param. No. Symbol Characteristic Min Max Units Conditions T07 ToeF2adR OESPP Falling Edge to CSSPP Rising Edge, Address Out 0 5 ns T08 ToeF2adV OESPP Falling Edge to Address Out Valid 0 5 ns T09 ToeR2adI OESPP Rising Edge to Address Out Invalid 0 5 ns T10 ToeF2daR OESPP Falling Edge to CSSPP Rising Edge, Data Out 0 5 ns T11 ToeF2daV OESPP Falling Edge to Address Out Valid 0 5 ns T12 ToeR2daI OESPP Rising Edge to Data Out Invalid 0 5 ns PIC18F2455/2550/4455/4550 DS39632E-page 404 © 2009 Microchip Technology Inc. TABLE 28-28: A/D CONVERTER CHARACTERISTICS: PIC18F2455/2550/4455/4550 (INDUSTRIAL) PIC18LF2455/2550/4455/4550 (INDUSTRIAL) FIGURE 28-23: A/D CONVERSION TIMING Param No. Symbol Characteristic Min Typ Max Units Conditions A01 NR Resolution — — 10 bit ΔVREF ≥ 3.0V A03 EIL Integral Linearity Error — — <±1 LSB ΔVREF ≥ 3.0V A04 EDL Differential Linearity Error — — <±1 LSB ΔVREF ≥ 3.0V A06 EOFF Offset Error — — <±2.0 LSB ΔVREF ≥ 3.0V A07 EGN Gain Error — — <±1 LSB ΔVREF ≥ 3.0V A10 — Monotonicity Guaranteed(1) — VSS ≤ VAIN ≤ VREF A20 ΔVREF Reference Voltage Range (VREFH – VREFL) 1.8 3.0 —— VDD – VSS VDD – VSS VV VDD < 3.0V VDD ≥ 3.0V A21 VREFH Reference Voltage High Vss + ΔVREF — VDD V A22 VREFL Reference Voltage Low VSS — VDD - ΔVREF V A25 VAIN Analog Input Voltage VREFL — VREFH V A30 ZAIN Recommended Impedance of Analog Voltage Source — — 2.5 kΩ A50 IREF VREF Input Current(2) —— —— 5 150 μA μA During VAIN acquisition. During A/D conversion cycle. Note 1: The A/D conversion result never decreases with an increase in the input voltage and has no missing codes. 2: VREFH current is from RA3/AN3/VREF+ pin or VDD, whichever is selected as the VREFH source. VREFL current is from RA2/AN2/VREF-/CVREF pin or VSS, whichever is selected as the VREFL source. 131 130 132 BSF ADCON0, GO Q4 A/D CLK A/D DATA ADRES ADIF GO SAMPLE OLD_DATA SAMPLING STOPPED DONE NEW_DATA (Note 2) 9 8 7 3 2 1 Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts. This allows the SLEEP instruction to be executed. 2: This is a minimal RC delay (typically 100 ns), which also disconnects the holding capacitor from the analog input. . . . . . . TCY(1) 0 TDIS © 2009 Microchip Technology Inc. DS39632E-page 405 PIC18F2455/2550/4455/4550 TABLE 28-29: A/D CONVERSION REQUIREMENTS Param No. Symbol Characteristic Min Max Units Conditions 130 TAD A/D Clock Period PIC18FXXXX 0.8 25.0(1) μs TOSC based, VREF ≥ 3.0V PIC18LFXXXX 1.4 25.0(1) μs VDD = 2.0V, TOSC based, VREF full range PIC18FXXXX — 1 μs A/D RC mode PIC18LFXXXX — 3 μs VDD = 2.0V, A/D RC mode 131 TCNV Conversion Time (not including acquisition time)(2) 11 12 TAD 132 TACQ Acquisition Time(3) 1.4 — μs -40°C to +85°C 135 TSWC Switching Time from Convert → Sample — (Note 4) 137 TDIS Discharge Time 0.2 — μs Note 1: The time of the A/D clock period is dependent on the device frequency and the TAD clock divider. 2: ADRES registers may be read on the following TCY cycle. 3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale after the conversion (VSS to VDD). The source impedance (RS) on the input channels is 50Ω. 4: On the following cycle of the device clock. PIC18F2455/2550/4455/4550 DS39632E-page 406 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 407 PIC18F2455/2550/4455/4550 29.0 DC AND AC CHARACTERISTICS GRAPHS AND TABLES Graphs and tables are not available at this time. PIC18F2455/2550/4455/4550 DS39632E-page 408 © 2009 Microchip Technology Inc. NOTES: © 2009 Microchip Technology Inc. DS39632E-page 409 PIC18F2455/2550/4455/4550 30.0 PACKAGING INFORMATION 30.1 Package Marking Information 28-Lead PDIP (Skinny DIP) XXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXX YYWWNNN Example PIC18F2455-I/SP 0810017 28-Lead SOIC XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX YYWWNNN Example PIC18F2550-E/SO 0810017 40-Lead PDIP XXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXX YYWWNNN Example PIC18F4455-I/P 0810017 Legend: XX...X Customer-specific information Y Year code (last digit of calendar year) YY Year code (last 2 digits of calendar year) WW Week code (week of January 1 is week ‘01’) NNN Alphanumeric traceability code Pb-free JEDEC designator for Matte Tin (Sn) * This package is Pb-free. The Pb-free JEDEC designator ( ) can be found on the outer packaging for this package. Note: In the event the full Microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. e3 e3 e3 e3 e3 PIC18F2455/2550/4455/4550 DS39632E-page 410 © 2009 Microchip Technology Inc. Package Marking Information (Continued) 44-Lead TQFP XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX YYWWNNN Example PIC18F4550 -I/PT 0810017 XXXXXXXXXX 44-Lead QFN XXXXXXXXXX XXXXXXXXXX YYWWNNN PIC18F4550 Example -I/ML 0810017 e3 e3 © 2009 Microchip Technology Inc. DS39632E-page 411 PIC18F2455/2550/4455/4550 30.2 Package Details The following sections give the technical details of the packages.                 !"   !"#$%&" '  ()"&'"!&) &#*& &  & #   +%&,  & !& - '! !#.#  &"#' #%!   & "! ! #%!   & "! !!  &$#/  !#  '! #&    .0 1,2 1!'!   &$& "! **& "&&  ! !" 3 & ' !&" & 4# *!( !!&    4 %&  &#& && 255***'    '5 4 6&! 7,8. 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