2014-05-22 22:13:20 +00:00
|
|
|
_Multiply: ; 37d41 (d:7d41)
|
|
|
|
ld a, $8
|
|
|
|
ld b, a
|
|
|
|
xor a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_PRODUCT], a ; $ff95
|
|
|
|
ld [H_MULTIPLYBUFFER], a ; $ff9b
|
|
|
|
ld [H_MULTIPLYBUFFER+1], a ; $ff9c
|
|
|
|
ld [H_MULTIPLYBUFFER+2], a ; $ff9d
|
|
|
|
ld [H_MULTIPLYBUFFER+3], a ; $ff9e
|
|
|
|
.multiplyLoop
|
|
|
|
ld a, [H_MULTIPLIER] ; $ff99
|
2014-05-22 22:13:20 +00:00
|
|
|
srl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLIER], a ; $ff99
|
|
|
|
jr nc, .smallMultiplier ; less than $80
|
|
|
|
; code to possibly multiply the multiplicand by 2 and divide the multiplier by 2?
|
|
|
|
ld a, [H_MULTIPLYBUFFER+3]
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_MULTIPLICAND+2]
|
2014-05-22 22:13:20 +00:00
|
|
|
add c
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLYBUFFER+3], a
|
|
|
|
ld a, [H_MULTIPLYBUFFER+2]
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_MULTIPLICAND+1]
|
2014-05-22 22:13:20 +00:00
|
|
|
adc c
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLYBUFFER+2], a
|
|
|
|
ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_MULTIPLICAND] ; $ff96
|
2014-05-22 22:13:20 +00:00
|
|
|
adc c
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLYDBUFFER+1], a ; $ff9c
|
|
|
|
ld a, [H_MULTIPLYBUFFER]
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_PRODUCT] ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
adc c
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLYBUFFER], a
|
|
|
|
.smallMultiplier
|
2014-05-22 22:13:20 +00:00
|
|
|
dec b
|
2015-07-26 21:04:24 +00:00
|
|
|
jr z, .done
|
|
|
|
ld a, [H_MULTIPLICAND]
|
2014-05-22 22:13:20 +00:00
|
|
|
sla a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLICAND+2], a
|
|
|
|
ld a, [H_MULTIPLICAND+1]
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLICAND+1], a
|
|
|
|
ld a, [H_MULTIPLICAND] ; $ff96
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_MULTIPLICAND], a ; $ff96
|
|
|
|
ld a, [H_PRODUCT] ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_PRODUCT], a ; $ff95
|
|
|
|
jr .multiplyLoop
|
|
|
|
.done
|
|
|
|
ld a, [H_MULTIPLYBUFFER+3]
|
|
|
|
ld [H_PRODUCT+3], a
|
|
|
|
ld a, [H_MULTIPLYBUFFER+2]
|
|
|
|
ld [H_PRODUCT+2], a
|
|
|
|
ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
|
|
|
|
ld [H_PRODUCT+1], a ; $ff96
|
|
|
|
ld [H_PRODUCT], a ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
ret
|
|
|
|
|
|
|
|
_Divide: ; 37da5 (d:7da5)
|
|
|
|
xor a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER], a ; ff9a
|
|
|
|
ld [H_DIVIDEBUFFER+1], a ; ff9b
|
|
|
|
ld [H_DIVIDEBUFFER+2], a ; ff9c
|
|
|
|
ld [H_DIVIDEBUFFER+3], a ; ff9d
|
|
|
|
ld [H_DIVIDEBUFFER+4], a ; ff9e
|
2014-05-22 22:13:20 +00:00
|
|
|
ld a, $9
|
|
|
|
ld e, a
|
|
|
|
.asm_37db3
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVIDEBUFFER]
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVIDEND+1] ; $ff96
|
2014-05-22 22:13:20 +00:00
|
|
|
sub c
|
|
|
|
ld d, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVISOR] ; $ff99
|
2014-05-22 22:13:20 +00:00
|
|
|
ld c, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVIDEND] ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
sbc c
|
|
|
|
jr c, .asm_37dce
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEND], a ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
ld a, d
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEND+1], a ; $ff96
|
|
|
|
ld a, [H_DIVIDEBUFFER+4]
|
2014-05-22 22:13:20 +00:00
|
|
|
inc a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER+4], a
|
2014-05-22 22:13:20 +00:00
|
|
|
jr .asm_37db3
|
|
|
|
.asm_37dce
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, b
|
2014-05-22 22:13:20 +00:00
|
|
|
cp $1
|
2015-07-26 21:04:24 +00:00
|
|
|
jr z, .done
|
|
|
|
ld a, [H_DIVIDEBUFFER+4]
|
2014-05-22 22:13:20 +00:00
|
|
|
sla a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER+4], a
|
|
|
|
ld a, [H_DIVIDEBUFFER+3]
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER+3], a
|
|
|
|
ld a, [H_DIVIDEBUFFER+2] ; $ff9c
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER+2], a ; $ff9c
|
|
|
|
ld a, [H_DIVIDEBUFFER+1]
|
2014-05-22 22:13:20 +00:00
|
|
|
rl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER+1], a
|
2014-05-22 22:13:20 +00:00
|
|
|
dec e
|
|
|
|
jr nz, .asm_37e04
|
|
|
|
ld a, $8
|
|
|
|
ld e, a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVIDEBUFFER]
|
|
|
|
ld [H_DIVISOR], a ; $ff99
|
2014-05-22 22:13:20 +00:00
|
|
|
xor a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER], a
|
|
|
|
ld a, [H_DIVIDEND+1] ; $ff96
|
|
|
|
ld [H_DIVIDEND], a ; $ff95
|
|
|
|
ld a, [H_DIVIDEND+2]
|
|
|
|
ld [H_DIVIDEND+1], a ; $ff96
|
|
|
|
ld a, [H_DIVIDEND+3]
|
|
|
|
ld [H_DIVIDEND+2], a
|
2014-05-22 22:13:20 +00:00
|
|
|
.asm_37e04
|
|
|
|
ld a, e
|
|
|
|
cp $1
|
|
|
|
jr nz, .asm_37e0a
|
|
|
|
dec b
|
|
|
|
.asm_37e0a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld a, [H_DIVIDEND+4] ; $ff99
|
2014-05-22 22:13:20 +00:00
|
|
|
srl a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_REMAINDER], a ; $ff99
|
|
|
|
ld a, [H_DIVIDEBUFFER]
|
2014-05-22 22:13:20 +00:00
|
|
|
rr a
|
2015-07-26 21:04:24 +00:00
|
|
|
ld [H_DIVIDEBUFFER], a
|
2014-05-22 22:13:20 +00:00
|
|
|
jr .asm_37db3
|
2015-07-26 21:04:24 +00:00
|
|
|
.done
|
|
|
|
ld a, [H_DIVIDEND+1] ; $ff96
|
|
|
|
ld [H_REMAINDER], a ; $ff99
|
|
|
|
ld a, [H_DIVIDEBUFFER+4]
|
|
|
|
ld [H_QUOTIENT+3], a
|
|
|
|
ld a, [H_DIVIDEBUFFER+3]
|
|
|
|
ld [H_QUOTIENT+2], a
|
|
|
|
ld a, [H_DIVIDEBUFFER+2] ; $ff9c
|
|
|
|
ld [H_QUOTIENT+1], a ; $ff96
|
|
|
|
ld a, [H_DIVIDEBUFFER+1]
|
|
|
|
ld [H_QUOTIENT], a ; $ff95
|
2014-05-22 22:13:20 +00:00
|
|
|
ret
|