Andrew Warren <fastfwd@IX.NETCOM.COM> answers a question about decrementing
W:
> If you're using a 12-bit PIC (16C5x), which doesn't have the "ADDLW"
> instruction, you can do this:
>      MOVWF   TEMP        ;Store W temporarily in a file register.
>      MOVLW   1           ;Subtract 1 from that register, leaving the
>      SUBWF   TEMP,W      ;result in W.

Or (saving one cycle):

        MOVWF   TEMP            ; TEMP := W;
        DECF    TEMP,W          ; W := TEMP - 1;

Eric