8-bit Divide: Difference between revisions

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rts
rts
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[[Category:Arithmetic]]

Revision as of 19:26, 8 October 2014

The following code divide two 8-bit integers (range 0...255) and outputs a 16-bit result using only real calculation, no lockup table so the size of the code is very small.

;8-bit divide
;by Bregalad
;Enter with A = Dividend, Y=Divisor
;Output with YA = (1/256)*(A/Y)
Division
	sta Dvd		;Stores divident
	sty Dvs		;Stores divisor
	lda #$00
	sta Res		;Clear result

	ldy #$10	;The loop is for 16-bit result
-	asl Dvd
	rol A		;Shift divisor in 1 bit
	cmp Dvs		;Check if fractional dividend is greater than divisor
	bcc +
	sbc Dvs 	;Substract (C is always set)
+	rol Res		;Shift result (1 if substation was done, 0 otherwise)
	rol Res2
	dey
	bne -
	lda Res
	ldy Res2
	rts