The basic structure of PIC microcontroller source program

    In order to quickly grasp the basic structure of the PIC microcontroller source program, a typical program structure framework is given here. When creating a source program, first use the pseudo-instruction TITLE to provide the program title, then give a general description of the entire program, and use the list pseudo-instruction LIST to specify the microcontroller model and file output format used, and then use the INCLUDE pseudo-instruction to read the definition file provided in MPASM, such as "P16F84?INC", and then define the commonly used resources in the chip, and then give the basic structure framework of the general program. An example is given below.

    TITLE "This is..."; program title

    ;Procedure Description

    LIST P=16F84，F=1NHX8M

    ;

    include

    -config_RC_Qsc&_WDT_0FF…

    ; Resource definition and variable definition

    STATUS EQU 03

    FSR EQU 04

    PORTA EQU 05

    PORTB EQU 06

    J EQU 01F

    K EQU 01E

    ;……

    ORG 0000 ;

    goto MAIN ; skip the interrupt vector

    ORG 0004

    goto INTSRV; subroutine entry address

    ;……

    MAIN; start the main program from 0005H

    call Initports; port initialization

    call InitTimers; timer initialization

    …

    INTSRV ... ;Interrupt service routine area

    SVBRTH… ; Subroutine area

    END ; program end character

    Of course, you can adjust it according to the actual situation when writing the program. The following is an actual program list, which requires writing data 88H into the 20H unit of the internal EEPROM of the PIC16F84, and then reading it out from the 20H unit.

    LIST P=16F84，F=INHX8M

    ;……

    STATUS EQU 03 ; define register

    EEDATA EQU 08

    EEADR EQU 09

    INTCON EQU 0BH

    EECON1 EQU 88H

    EECON2 EQU 89H

    ;……

    RD EQU 0 ；Define bit

    WR EQU 1

    RP0 EQU 5

    GIE EQU 7

    ;……

    ORG 0

    GOTO WRSTART

    ;……

    ORG 10H

    WRSTART ; write operation starts

    CLRW; Clear W, make W=0

    BCF STATUS, RP0; select BANK0

    MOVLW 20H

    MOVWF EEADR ; address → EEADR

    MOVLW 88H

    MOVWF EEDATA ；Write data→

    ;EEDATA

    BSF STATUS, RP0; select BANK1

    BSF EECON1, 2; Write operation enable

    BCF INTCON, GIE ; turn off all interrupts

    MOVLW 0X55

    MOVWF EECON2; 55H → EECON2

    MOVLW 0XAA

    MOVWF EECON2 ;AAH→EECON2

    BSF EECON1, WR; Start write operation

    BSF INTCON, GIE; Restore interrupt

    RDSTART ；Read operation starts

    BCF STATUS, RP0

    MOVLW 20H

    MOVWF EEADR ; address → EEADR

    BSF STATUS, RP0

    BSF EECON1, RD; start read operation

    BCF STATUS, RP0

    MOVF EEDATA, W ; EEPROM

    ; Data read into W

    END