Hi,

Your add routine may not work if the result of da2_l+da_1 has a carry
and da2_m is equal to 255 since it will become zero and the next
addition will be wrong.

Use the standard routine:

add32:
        movf    da2_l,w
        addwf   da1_l,f
        movf    da2_m,w
        skpnc
         incfsz da2_m,w
           addwf da1_m,f

        movf    da2_h,w
        skpnc
         incfsz da2_h,w
          addwf da1_h,f

regards,
Reggie

Keith Causey wrote:
>
> Hello All,
>     I am trying to debug a simple routine that adds two 32 bit numbers and I
> can't figure out why it keeps setting bits in the hi order bytes
> inappropriately. If you will take a look at this code and give some
> suggestions they would be much appreciated. The two arguments are in eight
> locations. Arg. 1 is, from least to most significant, in registers da1_l
> da1_m da1_h and da1_x. Arg. 2 is in da2_l da2_m da2_h and da2_x. On exit the
> sum is supposed to be in da1_l da1_m da1_h and da1_x.
> Here it is:
>   movf da2_l, W
>   addwf da1_l, SAME
>   btfsc CARRY
>   incf da2_m, SAME
>   btfsc ZERO
>   incf da2_h, SAME
>   btfsc ZERO
>   incf da2_x, SAME
>   movf da2_m, W
>   addwf da1_m, SAME
>   btfsc CARRY
>   incf da2_h, SAME
>   btfsc ZERO
>   incf da2_x, SAME
>   movf da2_h, W
>   addwf da1_h, SAME
>   btfsc CARRY
>   incf da2_x, SAME
>   movf da2_x, W
>   addwf da1_x, SAME
>                                         If you look at this code
>                                         Many Thanks
>                                         Keith Causey