;********************************************************************** list p=16f877A ; list directive to define processor #include ; processor specific variable definitions __CONFIG 0x3f32 ; '__CONFIG' directive is used to embed configuration data within .asm file. ; The lables following the directive are located in the respective .inc file. ; See respective data sheet for additional information on configuration word. ; errorlevel -302 ;***** VARIABLE DEFINITIONS w_temp EQU 0x71 ; variable used for context saving status_temp EQU 0x72 ; variable used for context saving tmp1 equ 0x73 tmp2 equ 0x74 ;********************************************************************** ORG 0x000 ; processor reset vector clrf PCLATH ; ensure page bits are cleared goto main ; go to beginning of program ORG 0x004 ; interrupt vector location movwf w_temp ; save off current W register contents movf STATUS,w ; move status register into W register movwf status_temp ; save off contents of STATUS register ; isr code can go here or be located as a call subroutine elsewhere bcf INTCON,T0IF ; clr flag T0IF movlw 0xff ; PORTC = !PORTC xorwf PORTC,f ; interupt code here !!!!!!!!!!!!!!!!! movf status_temp,w ; retrieve copy of STATUS register movwf STATUS ; restore pre-isr STATUS register contents swapf w_temp,f swapf w_temp,w ; restore pre-isr W register contents retfie ; return from interrupt main ; remaining code goes here bsf STATUS,RP0 movlw 0x06 movwf ADCON1 clrf TRISA clrf TRISB clrf TRISC clrf tmp1 clrf tmp2 movlw 0x87 ; tmr0 prescal 1:256 movwf OPTION_REG movlw b'10100000' ; timer0 intr enable movwf INTCON bcf STATUS,RP0 bcf ADCON0,ADON clrf PORTC et1 clrw movwf PORTA movwf PORTB call delay movlw 0xff movwf PORTA movwf PORTB call delay goto et1 delay decfsz tmp1,f goto delay decfsz tmp2,f goto delay return END ; directive 'end of program'