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https://github.com/pret/pokeyellow.git
synced 2026-05-09 12:22:04 -05:00
145 lines
2.9 KiB
NASM
Executable File
145 lines
2.9 KiB
NASM
Executable File
_Multiply: ; f660e (3d:660e)
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ld a, $8
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ld b, a
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xor a
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ld [H_PRODUCT], a ; $ff95
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ld [H_MULTIPLYBUFFER], a ; $ff9b
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ld [H_MULTIPLYBUFFER+1], a ; $ff9c
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ld [H_MULTIPLYBUFFER+2], a ; $ff9d
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ld [H_MULTIPLYBUFFER+3], a ; $ff9e
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.multiplyLoop
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ld a, [H_MULTIPLIER] ; $ff99
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srl a
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ld [H_MULTIPLIER], a ; $ff99
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jr nc, .smallMultiplier ; less than $80
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; code to possibly multiply the multiplicand by 2 and divide the multiplier by 2?
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ld a, [H_MULTIPLYBUFFER+3]
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ld c, a
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ld a, [H_MULTIPLICAND+2]
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add c
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ld [H_MULTIPLYBUFFER+3], a
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ld a, [H_MULTIPLYBUFFER+2]
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ld c, a
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ld a, [H_MULTIPLICAND+1]
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adc c
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ld [H_MULTIPLYBUFFER+2], a
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ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
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ld c, a
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ld a, [H_MULTIPLICAND] ; $ff96
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adc c
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ld [H_MULTIPLYBUFFER+1], a ; $ff9c
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ld a, [H_MULTIPLYBUFFER]
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ld c, a
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ld a, [H_PRODUCT] ; $ff95
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adc c
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ld [H_MULTIPLYBUFFER], a
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.smallMultiplier
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dec b
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jr z, .done
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ld a, [H_MULTIPLICAND+2]
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sla a
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ld [H_MULTIPLICAND+2], a
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ld a, [H_MULTIPLICAND+1]
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rl a
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ld [H_MULTIPLICAND+1], a
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ld a, [H_MULTIPLICAND] ; $ff96
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rl a
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ld [H_MULTIPLICAND], a ; $ff96
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ld a, [H_PRODUCT] ; $ff95
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rl a
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ld [H_PRODUCT], a ; $ff95
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jr .multiplyLoop
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.done
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ld a, [H_MULTIPLYBUFFER+3]
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ld [H_PRODUCT+3], a
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ld a, [H_MULTIPLYBUFFER+2]
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ld [H_PRODUCT+2], a
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ld a, [H_MULTIPLYBUFFER+1] ; $ff9c
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ld [H_PRODUCT+1], a ; $ff96
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ld a, [H_MULTIPLYBUFFER]
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ld [H_PRODUCT], a ; $ff95
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ret
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_Divide: ; f6672 (3d:6672)
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xor a
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ld [H_DIVIDEBUFFER], a ; ff9a
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ld [H_DIVIDEBUFFER+1], a ; ff9b
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ld [H_DIVIDEBUFFER+2], a ; ff9c
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ld [H_DIVIDEBUFFER+3], a ; ff9d
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ld [H_DIVIDEBUFFER+4], a ; ff9e
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ld a, $9
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ld e, a
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.asm_f6680
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ld a, [H_DIVIDEBUFFER]
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ld c, a
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ld a, [H_DIVIDEND+1] ; $ff96
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sub c
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ld d, a
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ld a, [H_DIVISOR] ; $ff99
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ld c, a
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ld a, [H_DIVIDEND] ; $ff95
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sbc c
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jr c, .asm_f669b
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ld [H_DIVIDEND], a ; $ff95
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ld a, d
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ld [H_DIVIDEND+1], a ; $ff96
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ld a, [H_DIVIDEBUFFER+4]
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inc a
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ld [H_DIVIDEBUFFER+4], a
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jr .asm_f6680
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.asm_f669b
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ld a, b
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cp $1
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jr z, .done
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ld a, [H_DIVIDEBUFFER+4]
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sla a
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ld [H_DIVIDEBUFFER+4], a
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ld a, [H_DIVIDEBUFFER+3]
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rl a
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ld [H_DIVIDEBUFFER+3], a
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ld a, [H_DIVIDEBUFFER+2] ; $ff9c
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rl a
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ld [H_DIVIDEBUFFER+2], a ; $ff9c
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ld a, [H_DIVIDEBUFFER+1]
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rl a
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ld [H_DIVIDEBUFFER+1], a
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dec e
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jr nz, .asm_f66d1
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ld a, $8
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ld e, a
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ld a, [H_DIVIDEBUFFER]
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ld [H_DIVISOR], a ; $ff99
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xor a
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ld [H_DIVIDEBUFFER], a
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ld a, [H_DIVIDEND+1] ; $ff96
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ld [H_DIVIDEND], a ; $ff95
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ld a, [H_DIVIDEND+2]
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ld [H_DIVIDEND+1], a ; $ff96
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ld a, [H_DIVIDEND+3]
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ld [H_DIVIDEND+2], a
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.asm_f66d1
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ld a, e
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cp $1
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jr nz, .asm_f66d7
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dec b
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.asm_f66d7
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ld a, [H_DIVISOR] ; $ff99
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srl a
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ld [H_DIVISOR], a ; $ff99
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ld a, [H_DIVIDEBUFFER]
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rr a
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ld [H_DIVIDEBUFFER], a
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jr .asm_f6680
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.done
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ld a, [H_DIVIDEND+1] ; $ff96
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ld [H_REMAINDER], a ; $ff99
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ld a, [H_DIVIDEBUFFER+4]
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ld [H_QUOTIENT+3], a
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ld a, [H_DIVIDEBUFFER+3]
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ld [H_QUOTIENT+2], a
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ld a, [H_DIVIDEBUFFER+2] ; $ff9c
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ld [H_QUOTIENT+1], a ; $ff96
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ld a, [H_DIVIDEBUFFER+1]
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ld [H_QUOTIENT], a ; $ff95
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ret
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