list p=pic16f84a
include p16f84a.inc
__config _HS_OSC & _WDT_OFF & _PWRTE_ON & _CP_OFF
errorlevel -302 ;
cblock h'0c'
count1
count2
endc
;**************** Program Start ***********************
org 0
goto start
;**************** Initial Process *********************
start
bsf STATUS,RP0
movlw h'ff'
movwf TRISA
clrf TRISB
bcf STATUS,RP0
movlw h'ff'
movwf PORTB
bsf INTCON,F
loop
movlw 0xff
movwf PORTB
call timer
movlw 0x00
movwf PORTB
call timer
goto loop
timer
movlw d'25'
movwf count1
lp0
movlw d'250'
movwf count2
lp1
decfsz count2,F
goto lp1
decfsz count1,F
goto lp0
return
end