8-bit Divide: Difference between revisions
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;Output with YA = (1/256)*(A/Y) | ;Output with YA = (1/256)*(A/Y) | ||
Division | Division | ||
sta Dvd ;Stores divident | |||
sty Dvs | sty Dvs ;Stores divisor | ||
lda #$00 | lda #$00 | ||
sta Res | sta Res ;Clear result | ||
ldy #$10 | ldy #$10 ;The loop is for 16-bit result | ||
- asl Dvd | - asl Dvd | ||
rol A ;Shift divisor in 1 bit | rol A ;Shift divisor in 1 bit | ||
cmp Dvs | cmp Dvs ;Check if fractional dividend is greater than divisor | ||
bcc + | bcc + | ||
sbc Dvs ;Substract (C is always set) | sbc Dvs ;Substract (C is always set) | ||
+ rol Res | + rol Res ;Shift result (1 if substation was done, 0 otherwise) | ||
rol Res2 | rol Res2 | ||
dey | dey | ||
Revision as of 07:34, 25 August 2013
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.
<source lang="6502">
- 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 </source>
