61 lines
1.3 KiB
NASM
61 lines
1.3 KiB
NASM
;divide by 2 example
|
|
; 0 1 2 3 4 5 6 7 8 9 a b c d e f 10--Offset Ruler
|
|
;v 00 01 01 02 02 03 03 04 04 04 05 05 06 06 07 07 08
|
|
|
|
;divide by 3 example
|
|
; 0 1 2 3 4 5 6 7 8 9 a b c d e f 10 11 12 13 14 15 16 17 18
|
|
;00 00 01 01 01 02 02 02 03 03 03 04 04 04 05 05 05 06 06 06 07 07 07 08 08
|
|
|
|
MultiplyByY:
|
|
.loop cpy #$0001 : beq .done
|
|
cpy #$0003 : bne ++
|
|
jsr MultiBy3 : bra .done
|
|
++ cpy #$0005 : bne ++
|
|
jsr MultiBy5 : bra .done
|
|
++ asl : sta $00 : tya : lsr : tay : lda $00 : bra .loop
|
|
.done rts
|
|
|
|
;todo -- width in X?
|
|
DivideByY:
|
|
.loop cpy #$0001 : beq .done
|
|
cpy #$0003 : bne ++
|
|
jsr DivideBy3 : bra .done
|
|
++ cpy #$0005 : bne ++
|
|
jsr DivideBy5 : bra .done
|
|
; todo -- alter - width
|
|
++ tyx : jsr DivideBy2 : sta $00 : tya : lsr : tay : lda $00 : bra .loop
|
|
.done rts
|
|
|
|
MultiBy3:
|
|
sta $00 : asl : !add $00
|
|
rts
|
|
|
|
MultiBy5:
|
|
sta $00 : asl #2 : !add $00
|
|
rts
|
|
|
|
;width of divison in x
|
|
DivideBy2:
|
|
sta $00
|
|
lsr : bcc .done
|
|
sta $02 : txa : lsr : cmp $00 : !bge .done
|
|
lda $02 : inc
|
|
.done rts
|
|
|
|
DivideBy3:
|
|
sta $00
|
|
ldx #$0000
|
|
lda #$0002
|
|
.loop cmp $00 : !bge .store
|
|
inx : !add #$0003 : bra .loop
|
|
.store txa
|
|
rts
|
|
|
|
DivideBy5:
|
|
sta $00
|
|
ldx #$0000
|
|
lda #$0003
|
|
.loop cmp $00 : !bge .store
|
|
inx : !add #$0005 : bra .loop
|
|
.store txa
|
|
rts |