Using a PIC16C84, I have written some code for my electronic gate. The first
part  goes  like this...


;******************************************************************
;       THIS SECTION SETS UP THE I/O PINS ON PORT A AND B         *
;******************************************************************

        BSF     STATUS,RP0      ;CLEAR RP0 IN STATUS REGISTER
        MOVLW   B'0000000'      ;MOVE BINARY TO W
        MOVWF   PORTA           ;SET A0-A4 AS OUTPUTS
        MOVLW   B'11111111'     ;MOVE BINARY TO W
        MOVWF   PORTB           ;SET B0-B7 AS INPUTS
        MOVLW   B'00000100'
        MOVWF   OPTION_REG      ;ENABLE PORTB PULLUP
        BCF     STATUS,RP0      ;SELECT PAGE 0
        CLRF    PORTA           ;CLEAR PORTA
        CLRF    PORTB           ;CLEAR PORTB

and the second ( added later on  and causing the problem )goes like this...


INIT_TIMER

;       BSF     STATUS,RP0
;       MOVLW   B'00000100'             ;DIVIDE BY 32,ENABLE PULLUP
;       MOVWF   OPTION_REG
        BCF     STATUS,RP0
        MOVLW   B'10100000'
        MOVWF   INTCON
;       MOVLW   .102
;       MOVWF   TMR0

the parts that are remmed out were me trying to find the problem. What
happens is that the pullup does not seem to work with the second code
section added. Using the timer interupt was an addition. In the first part
of the code I specificaly cleared the pullup bit to enable it. I can't  get
it to work together and I don't know why. Please help
Gordon  Zerf

Director - KerZer Computers