On Tue, 21 Apr 1998, Regulus Berdin wrote:

> > From: T. Scott Dattalo <sdattalo@UNIX.SRI.COM>
> snip
> > These routines will not work on the '5x parts because
> > of the ADDLW instruction. (but maybe Reggie will fix that)
>
> I'll try:
>
> BCD_ADD:                        ;Y = Y + X
>         MOVLW   66
>         ADDWF   X,W
>         ADDWF   Y,F
>         MOVLW   -60
>         SKPDC
>          MOVLW  -66
>         SKPC
>          ADDWF  Y,F
>         RETLW   0

Close, but try X = 0x95 and Y = 0x95. The correct answer should
be Y=0x80 and C=1. However, this routine will produce Y=0x2A and
C=1. You still need that annoying normalization step.

> BCD_MINUS:                      ;Y = Y - X
>         MOVF    X,W
>         SUBWF   Y,F
>         MOVLW -6
>         SKPC
>          MOVLW  -66
>         SKPDC
>          ADDWF  Y,F
>         RETLW   0

Try X=0x25, Y=0x16. This produces 0xf1 instead of 0x91.

>
> Sorry, there are no comments :) , it is difficult to explain.

Yeah... tell that to Bill

Scott