PIC Programming in C and Assembly
Krerk Piromsopa, Ph.D.
Department of Computer Engineering Chulalongkorn University
Outlines
• Microprocessor vs. MicroController
• PIC in depth
• PIC Programming
• Assembly Programming
• Embedded C
• In-line assembly
• PIC Interface
Microcontroller vs. Microprocessor Microcontroller vs. Microprocessor
Microcontroller vs. Microprocessor Microcontroller vs. Microprocessor
Figures from http://www.mhennessy.f9.co.uk/pic/introduction.htm
PIC in depth
PIC16F87X
DS30292C-page 6 2001 Microchip Technology Inc.
FIGURE 1-2: PIC16F874 AND PIC16F877 BLOCK DIAGRAM
FLASH Program Memory
13 Data Bus 8
Program14 Bus
Instruction reg Program Counter
8 Level Stack (13-bit)
RAM File Registers
Direct Addr 7 RAM Addr(1) 9
Addr MUX Indirect
Addr FSR reg
STATUS reg
MUX
ALU
W reg Power-up
Timer Oscillator Start-up Timer
Power-on Reset Watchdog
Timer Instruction Decode &
Control
Timing Generation OSC1/CLKIN OSC2/CLKOUT
MCLRVDD, VSS
PORTA
PORTB
PORTC
PORTD
PORTE RA4/T0CKI RA5/AN4/SS
RC0/T1OSO/T1CKI RC1/T1OSI/CCP2 RC2/CCP1 RC3/SCK/SCL RC4/SDI/SDA RC5/SDO RC6/TX/CK RC7/RX/DT
RE0/AN5/RD RE1/AN6/WR RE2/AN7/CS 8
8
Brown-out Reset
Note 1:Higher order bits are from the STATUS register.
USART
CCP1,2 Synchronous
10-bit A/D
Timer0 Timer1 Timer2
Serial Port
RA3/AN3/VREF+
RA2/AN2/VREF- RA1/AN1 RA0/AN0
Parallel Slave Port 8
3
Data EEPROM
RB0/INT RB1 RB2 RB3/PGM RB4 RB5 RB6/PGC RB7/PGD Device Program
FLASH Data Memory Data EEPROM
PIC16F874 4K 192 Bytes 128 Bytes
PIC16F877 8K 368 Bytes 256 Bytes
In-Circuit Debugger Low-Voltage Programming
RD0/PSP0 RD1/PSP1 RD2/PSP2 RD3/PSP3 RD4/PSP4 RD5/PSP5 RD6/PSP6 RD7/PSP7
Memory Model
2001 Microchip Technology Inc. DS30292C-page 11
PIC16F87X
2.0 MEMORY ORGANIZATION There are three memory blocks in each of the PIC16F87X MCUs. The Program Memory and Data Memory have separate buses so that concurrent access can occur and is detailed in this section. The EEPROM data memory block is detailed in Section 4.0.
Additional information on device memory may be found in the PICmicro Mid-Range Reference Manual, (DS33023).
FIGURE 2-1: PIC16F877/876 PROGRAM MEMORY MAP AND STACK
2.1 Program Memory Organization The PIC16F87X devices have a 13-bit program counter capable of addressing an 8K x 14 program memory space. The PIC16F877/876 devices have 8K x 14 words of FLASH program memory, and the PIC16F873/874 devices have 4K x 14. Accessing a location above the physically implemented address will cause a wraparound.
The RESET vector is at 0000h and the interrupt vector is at 0004h.
FIGURE 2-2: PIC16F874/873 PROGRAM MEMORY MAP AND STACK
PC<12:0>13
0000h
0004h 0005h Stack Level 1
Stack Level 8
RESET Vector
Interrupt Vector
On-Chip CALL, RETURN RETFIE, RETLW
1FFFh Stack Level 2
Program Memory
Page 0
Page 1
Page 2
Page 3
07FFh 0800h
0FFFh 1000h
17FFh 1800h
PC<12:0>
13
0000h
0004h 0005h Stack Level 1
Stack Level 8
RESET Vector
Interrupt Vector
On-Chip CALL, RETURN RETFIE, RETLW
1FFFh Stack Level 2
Program Memory
Page 0
Page 1
07FFh 0800h
0FFFh 1000h
Register File Map
2001 Microchip Technology Inc. DS30292C-page 13
PIC16F87X
FIGURE 2-3: PIC16F877/876 REGISTER FILE MAP
Indirect addr.(*) TMR0
PCL STATUS
FSR PORTA PORTB PORTC
PCLATH INTCON PIR1
TMR1L TMR1H T1CON TMR2 T2CON SSPBUF SSPCON CCPR1L CCPR1H CCP1CON
OPTION_REG PCL STATUS
FSR TRISA TRISB TRISC
PCLATH INTCON PIE1
PCON
PR2 SSPADD SSPSTAT 00h 01h 02h 03h 04h 05h 06h 07h 08h 09h 0Ah 0Bh 0Ch 0Dh 0Eh 0Fh 10h 11h 12h 13h 14h 15h 16h 17h 18h 19h 1Ah 1Bh 1Ch 1Dh 1Eh 1Fh
80h 81h 82h 83h 84h 85h 86h 87h 88h 89h 8Ah 8Bh 8Ch 8Dh 8Eh 8Fh 90h 91h 92h 93h 94h 95h 96h 97h 98h 99h 9Ah 9Bh 9Ch 9Dh 9Eh 9Fh
20h A0h
7Fh FFh
Bank 0 Bank 1
Unimplemented data memory locations, read as ’0’.
* Not a physical register.
Note 1:These registers are not implemented on the PIC16F876.
2:These registers are reserved, maintain these registers clear.
File Address Indirect addr.(*) Indirect addr.(*)
PCL STATUS
FSR
PCLATH INTCON
PCL STATUS
FSR
PCLATH INTCON 100h 101h 102h 103h 104h 105h 106h 107h 108h 109h 10Ah 10Bh 10Ch 10Dh 10Eh 10Fh 110h 111h 112h 113h 114h 115h 116h 117h 118h 119h 11Ah 11Bh 11Ch 11Dh 11Eh 11Fh
180h 181h 182h 183h 184h 185h 186h 187h 188h 189h 18Ah 18Bh 18Ch 18Dh 18Eh 18Fh 190h 191h 192h 193h 194h 195h 196h 197h 198h 199h 19Ah 19Bh 19Ch 19Dh 19Eh 19Fh
120h 1A0h
17Fh 1FFh
Bank 2 Bank 3
Indirect addr.(*)
PORTD(1) PORTE(1)
TRISD(1)
ADRESL TRISE(1)
TMR0 OPTION_REG
PIR2 PIE2
RCSTA TXREG RCREG CCPR2L CCPR2H CCP2CON ADRESH ADCON0
TXSTA SPBRG
ADCON1
General Purpose Register
General Purpose Register
General Purpose Register
General Purpose Register
1EFh accesses 1F0h 70h - 7Fh EFh
accesses F0h 70h-7Fh
16Fh accesses 170h 70h-7Fh General Purpose Register
General Purpose Register TRISB PORTB
96 Bytes 80 Bytes 80 Bytes 80 Bytes
16 Bytes 16 Bytes
SSPCON2
EEDATA EEADR
EECON1 EECON2 EEDATH
EEADRH
Reserved(2) Reserved(2) AddressFile File
Address File
Address AddressFile
Device?
• I/O Port
• EEPROM
• Timer & PWM
• Serial Port
• A2D
• Interrupt
• Watchdog Timer
Can you use any of them?
Assembly 101
• Assembly is the language closest to hardware level (machine language level).
• Why assembly?
• Low level
• speed
• time critical
• small program size
When to program in assembly?
Development Cycle
Component of Assembly
• Labels
• start in column 1. may follow by a colon (:), space, tab or the end of line.
• begin with an alpha character or an under bar (_) and may contain alphanumeric characters, the under bar and the question mark.
• Mnemonics, Directives and Macros
• Operands
• Comments
Example
list p=18f452 #include p18f452.inc
Dest equ 0x0B ;Define constant org 0x0000 ;Reset vector goto Start
org 0x0020 ;Begin program Start
movlw 0x0A movwf Dest
bcf Dest, 3 ;This line uses 2 operands
goto Start end
Notice the directive
List File
--- C:\PIC\SAMPLE.ASM --- 1: list p=16f877 , b=2, c=80 2: #include p16f877.inc
3: Dest equ 0x0B ;Define constant 4:
org 0x0000 ;Reset vector 0000 2820 GOTO 0x20 5: goto Start
6:
org 0x0020 ;Begin program 7: Start
0020 300A MOVLW 0xa 8: movlw 0x0A 0021 008B MOVWF 0xb 9: movwf Dest
0022 118B BCF 0xb, 0x3 10: bcf Dest, 3 ;This line uses 2 operands 0023 2820 GOTO 0x20 11: goto Start
Notice the directive
Quick tip
Use “banksel” directive to avoid bank switching issue.
0020 1683 BSF 0x3, 0x5 8: banksel TRISB 0022 3000 MOVLW 0 9: ! movlw! 0x00 0023 0086 MOVWF 0x6 10: ! movwf! TRISB
BSF STATUS,RS0
movlw! 0x00
movwf! TRISB
Macro
OutPort!macro!myport, myvalue
! ! banksel!myport
! ! movlw!myvalue
! ! movwf!myport
! ! endm BCF 0x3, 0x5
MOVLW 0x55 MOVWF PORTB BCF 0x3, 0x5 MOVLW 0xaa MOVWF PORTA
OutPort PORTB, 0x55 OutPort PORTA, 0xAA
Advanced Macro
Add1_x !macro!x
! ! local!i=0
! ! clrw
! ! while i<x
! ! ! addlw ! i!
! ! ! i += 1
! ! endw
! ! endm
Add1_x! 10
; This will give CLRW
ADDLW 0 ADDLW 0x1 ADDLW 0x2 ....
....
ADDLW 0xe ADDLW 0xf
See MPASM HELP for more details.
Embedded C
Lab1 in C
#include <pic16f87.h>
void main (void) {
! TRISB=0x01;
! while ( 1 ) {
! if (RB0) {
! ! PORTB |=0x02;
! ! PORTB &=0xFB;
! ! //PORTB=0x02;
! } else {
! ! PORTB |=0x04;
! ! PORTB &=0xFD;
! ! //PORTB=0x04;
! }
! }
}
Mix C and Assembly
#include <pic16f87.h>
void main (void) {
! TRISB=0x01;
! while ( 1 ) {
! if (RB0) {
! ! #asm
! ! BSF!_PORTB, 1
! ! BCF!_PORTB, 2
! ! #endasm
! } else {
! ! asm("BCF! _PORTB, 1");
! ! asm("BSF! _PORTB, 2");
! }
! } }
Inline assembly
Use #asm and #endasm for multiple line.
Use asm(“ “) for single line Add _ to variable in C
Good library can help inexperience
programmer.
See 16 adders in C
int sum(int i, int j) {
! int sum;
! sum=i+j;
! return sum;
}
CLRF 0x3 MOVF 0x22, W ADDWF 0x20, W MOVWF 0x20 MOVF 0x23, W BTFSC 0x3, 0 INCF 0x23, W ADDWF 0x21, W MOVWF 0x21 MOVWF 0x7f MOVF 0x20, W MOVWF 0x7e RETURN
How is your LAB 2?
What if there is no library to do your job?
How to use C in my LAB?
When to write in C?
When to write in Assembly?
POP Quiz:
Will recursive program work in PIC?
