Dave Celsnak <x93celsnak@wmich.edu> wrote:

> I believe I have a bug in my ISR (PIC 16c72).
> I am willing to give-up an arm for this one:
> ....
>                 movwf   _WTEMP
>                 swapf   STATUS,0
>                 bcf     STATUS,5
>                 movwf   _STATTEMP
>                 swapf   FSR,0
>                 movwf   _FSRTEMP
>                 swapf   PCLATH,0
>                 movwf   _PCLTEMP
>                 ....
>                 bcf     STATUS,5
>                 movf    _PCLTEMP,0
>                 movwf   PCLATH
>                 movf    _FSRTEMP,0
>                 movwf   FSR
>                 swapf   _STATTEMP,0
>                 movwf   STATUS
>                 swapf   _WTEMP,1
>                 swapf   _WTEMP,0 RETI

Dave:

If you're going to use SWAPFs to save your FSR and PCLATH values,
you also need to use SWAPFs when you restore them.

Personally, I'd leave the "restore" code alone and change the "save"
code to:

    movwf   _WTEMP
    swapf   STATUS,0
    bcf     STATUS,5
    movwf   _STATTEMP
    movf    FSR,0
    movwf   _FSRTEMP
    movf    PCLATH,0
    movwf   _PCLTEMP

-Andy

=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499