1. list p=16f877
#include <p16f877.inc >
__CONFIG _CP_OFF &_WDT_OFF & _BODEN_ON & _PWRTE_ON & _XT_OSC & _WRT_ENABLE_OFF &
_LVP_OFF & _DEBUG_OFF & _CPD_OFF
bsf STATUS,RP0
movlw b'00000111'
movwf ADCON1
movlw b'00000000'
movwf TRISD
movlw b'11111111'
movwf TRISA
bcf STATUS,RP0
movlw b'11111111'
movwf PORTA
movwf PORTD
START
btfsc PORTA,0
goto START
movlw b'00000000'
movwf PORTD
end