Sorry guys I fat fingered my previous message.  Here's the rest of it.

Guys, I have a value in W that's signed.  Adding this value to a set of two
variables is easy enough:
addwf     blahL,f
clrf         wreg
addwfc   blahH,f

W contains a signed value.  If the value of W is a negative, doing the
following doesn't work (to subtract it instead of adding it.)

    addwf    blahL,f
     clrf        wreg
     bnc       subtract
     addwfc blahH,f
subtract
     subwfb, blahH,F

I see why this is incorrect, but I'm not sure how you test for a 2's
complement value in order to properly skip the subtraction if the value in W
is not setting the carry or borrow flag when adding the lower byte.  Can
someone please steer me down the correct path?

Regards,
Bob





On 7/14/06, Bob J. <rocketbob@gmail.com> wrote:
>
> Guys, I have a value in W that's signed.  Adding this value to a set of
> two variables is easy enough:
>
> addwf     blah,f
> clrf         wreg
> addwfc
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist