Rikard,

Did you clear the ANSEL register?  All the A/D pins default to analog 
mode on reset.

Bill

Rikard Bosnjakovic wrote:

>I've built a small cable-tester. In a loop, I have these lines:
>
>        movlw   b'00000001'         ; run cable test on GP0
>        movwf   GPIO
>        call    delay_500ms
>
>        movlw   b'00000010'         ; run cable test on GP1
>        movwf   GPIO
>        call    delay_500ms
>
>        movlw   b'00000100'         ; run cable test on GP2
>        movwf   GPIO
>        call    delay_500ms
>
>        movlw   b'00010000'         ; run cable test on GP4
>        movwf   GPIO
>        call    delay_500ms
>
>        movlw   b'00100000'         ; run cable test on GP5
>        movwf   GPIO
>        call    delay_500ms
>
>Each of the corresponding GPs are connected to an LED and an
>(external) AND-gate. The problem is, none of the LEDs are being lit
>when using the above code.
>
>Even more weird, if I insert this piece of test-code (light all LEDs):
>
>        movlw   -1
>        movwf   GPIO
>        call    delay_500ms
>        clrf    GPIO
>        call    delay_500ms
>
>between the GP0/GP1 tests above, all LEDs are being lit.
>Step-debugging in MPLAB and watching the GPIO, I clearly see
>"00000001", "00000010" etc in GPIO for the various tests, but none of
>them are being lit.
>
>I also tried this:
>
>    movlw b'11111100'
>    movwf GPIO
>    call delay_500ms
>
>Then the LEDs are instantly flashing (for like 0.1 ms, just barely
>noticeable) before turned off.
>
>I've been scratching my head for a couple of hours now,
>double-checking the datasheets but I just can't see what's wrong. It
>works for all the LEDs at the same time, but not one at a time.
>
>Can anyone explain what's happening? Could it be a RMW-problem? I
>can't think of anything right now.
>
>
>  
>

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