On Tue, 2004-01-13 at 12:43, Michael Johnston wrote:
> Tony
>     Here is my code you asked for. My delay was adapted from some code on
> the pic list archive.
> thanks

You've a lot of unnecessary stuff and the delays are misplaced. I'm
relatively new to PICs but these are my observations and example code,

* don't need counter since last bit already serves as a limit so no need
to check Z either.
* before you set the next bit check it is not the last bit
* set the next bit then delay not the other way around
* don't need to clear C since your rotates should never carry and you
never checked it anyway

;put your setup stuff here

start_condition
        clrf    PORTB           ;clear all portb
        movf    0x01
        movwf   PORTA           ;set only pin0 on porta
pointaf
        btfsc   PORTA,3         ;if bit 3 is lit
        goto    change_ab       ;then we're ready to change ports
        rlf     PORTA,same      ;otherwise rotate
        call    delay
        goto    pointaf
change_ab
        clrf    PORTA           ;finished with porta for now
        bsf     PORTB,0         ;set bit 0 on portb
                                ;others are already off
pointbf
        btfsc   PORTB,7         ;if bit 7 is lit
        goto    pointbr         ;then we're ready to reverse
        rlf     PORTB,same      ;otherwise rotate
        call    delay
        goto    pointbf
pointbr
        btfsc   PORTB,0         ;if bit 0 is lit
        goto    change_ba       ;then we're ready to change ports
        rrf     PORTB,same      ;otherwise rotate
        call    delay
        goto    pointbr
change_ba
        clrf    PORTB           ;finished with portb for now
        bsf     PORTA,3         ;set bit 3 on porta
                                ;others are already off
pointar
        btfsc   PORTA,0         ;if bit 0 is lit
        goto    pointaf         ;then we're ready to start again
        rrf     PORTA,same      ;otherwise rotate
        call    delay
        goto    pointar

        goto    start_condition ;should never get to here
                                ;but just in case

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