Bob Fehrenbach wrote:
>
> Bob Blick <bblick@TELIS.ORG> wrote:
>
> >>        movf    Source,w
> >>        btfsc   C
> >>         incfsz Source,w
> >>         addwf  Dest,f
>
> >Please continue with the explanation of this one, I'm not quick enough to
> >figure out what you're doing.
>
> Bob,
>
> Perhaps a whole macro would illustrate:
>
>    ;Two byte add.   Standard PIC instruction set does not have an add
>    ;with carry instruction.
>    ;At exit, if C = 1, result is greater than 2 bytes.
>    ;Usage example:  add_word buff, new_data
>
> add_word: macro aaa, bbb
>    movf    (bbb+1), w
>    addwf   (aaa+1), f
>    movf    (bbb), w
>    skpnc
>    incfsz  (bbb), w
>    addwf   (aaa), f
>    endm
>
> Bob
>
> --
> Bob Fehrenbach    Wauwatosa, WI     bfehrenb@execpc.com

And as Bob F. and I were recently discussing, this comes from
Microchip's
AN617. The author is Frank Testa. Someone correct me if I wrong, but I
believe Frank has a PhD in physics.

Scott