Bob Segrest <bobslan@EROLS.COM> wrote:
>Can
>anyone provide me with a sixteen bit subtraction routine example ???

   Try these:

;*******************************************************************
;  Two byte subtract.
;  At exit, if C = 1, result is positive.
;  Usage example:   sub_word new_count, old_count
;  Note: Zero flag NOT valid at exit
;*******************************************************************

sub_word: macro aaa, bbb
   movf    (bbb+1), w
   subwf   (aaa+1), f
   movf    (bbb), w
   skpc
   incfsz  (bbb), w
   subwf   (aaa), f
   endm

;*******************************************************************
;  Subtract two byte literal.
;  At exit, C = 0 if result is negative
;  Note: Zero flag NOT valid at exit
;*******************************************************************

sub_word_literal: macro aaa, lll

   movlw   low (~(lll) + 1)
   addwf   aaa+1, f
   movlw   high ((~(lll) + 1) & h'ffff')
   skpnc
   addlw   1
   skpnc
   skpz
   addwf   aaa, f
   endm

;*******************************************************************

--
Bob Fehrenbach    Wauwatosa, WI     bfehrenb@execpc.com