>
> Scan_Keys:      movf    PORTB,w         ;
>                  movwf       scratchpad      ;put PORTB in a temp register
>                 xorwf   keys,w          ;compare to last rounds winners
>                 btfsc   STATUS,Z        ;Z=0 if same

The comment and the instruction don't quite match up. Z=1 if
keys = scratchpad. It's a little confusing at first glance, especially
if you haven't even had your first morning cuppa ;-)

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