;
; *** Listing 9-20 ***
;
; Times the performance of SUB with memory as the
; destination operand and a register as the source operand.
;
	jmp	Skip
;
Dest	db	0
;
Skip:
	call	ZTimerOn
	rept	1000
	sub	[Dest],al	;subtract AL from [Dest]
				; Two memory accesses are
				; performed
	endm
	call	ZTimerOff