di2493.txt
;*****************************************************************************************************
; LISTING 1 - COMPARISON MACRO
;
; "Comparison macro for PIC processors," EDN, March 2, 2000, pg 122
; 
; http://www.ednmag.com/ednmag/reg/2000/030200/designideas.htm#05di4
;****************************************************************************************************
	

#define eq		1		; if equal
#define ne		2		; if not equal
#define bl		3		; if below (unsigned comparison)
#define ae		4		; if above or equal (unsigned)
#define WREG	0xFFFD	; if immediate-value specified as the W reg

b2 		MACRO		target, ram_reg, cond, lval 
	nolist
	if lval != WREG		; if lval spec'd as "WREG", don't move lval to W
		movlw	lval
	endif
; subtract will set carry if ram_reg >= lval, clear it if reg < lval (unsigned)
		subwf	ram_reg, W	; ram_reg minus W -> W, ram_reg unchanged
	if cond == eq		; if cond is "eq", skip if non 0, branch if 0
		skpnz
	else
	 if cond == ne		; if cond is "ne", skip if 0, branch if non 0
	 	skpz
	 else
	  if cond == bl		; if cond is "bl", skip if carry, branch if not
	  	skpc
	  else
	   if cond == ae		; if cond is "ae", skip if not carry, else branch
	   	skpnc
	   else			; if condition none of the above, error
	   	error	"b2 macro condition argument not a valid choice"
           endif		; cond = ae
          endif		; cond = bl
	 endif		; cond = ne
	endif			; cond = eq
		b	target	; skip this if condition not true, take it if true
	list
		ENDM	; b2