list p=16f876a
#include <p16f876a.inc>
__CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _XT_OSC & _WRT_OFF & _LVP_OFF & _CPD_OFF
cblock 0x20
CounterA
CounterB
CounterC
endc
org 0x0000
goto main
org 0x0004
retfie
main:
bsf STATUS, RP0
movlw 0x0
movwf PORTB
movwf PORTC
bcf STATUS, RP0
Loop
movlw 0xff
movwf PORTC
movwf PORTB
call Delay
movlw 0x00
movwf PORTC
movwf PORTB
call Delay
goto Loop
Delay
movlw D'6'
movwf CounterC
movlw D'24'
movwf CounterB
movlw D'168'
movwf CounterA
loop
decfsz CounterA,1
goto loop
decfsz CounterB,1
goto loop
decfsz CounterC,1
goto loop
retlw 0x00
END