127 lines
1.9 KiB
NASM
127 lines
1.9 KiB
NASM
;; cpHLDE [Maths]
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;; Compares HL to DE.
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;; Output:
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;; Same as z80 CP instruction.
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cpHLDE:
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or a
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sbc hl, de
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add hl,de
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ret
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;; cpHLBC [Maths]
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;; Compares HL to BC.
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;; Output:
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;; Same as z80 CP instruction.
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cpHLBC:
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or a
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sbc hl, bc
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add hl,bc
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ret
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;; cpBCDE [Maths]
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;; Compares DE to BC.
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;; Output:
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;; Same as z80 CP instruction.
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cpBCDE:
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push hl
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ld h, b
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ld l, c
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or a
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sbc hl, de
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pop hl
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ret
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;; mulAbyB
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;; Multiplys AxB
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;; Inputs:
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;; A: Multiplier
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;; B: Multiplicand
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;; Outputs:
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;; A: Product of A and B.
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mulAbyB:
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push bc
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ld c, a
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mulAbyBLoop:
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add a, c
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djnz mulAbyBLoop
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sub c
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pop bc
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ret
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;; mul8By8 [Maths]
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;; Performs an unsigned multiplication of H and E
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;; Inputs:
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;; H: Multiplier
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;; E: Multiplicand
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;; Outputs:
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;; HL: Product of H and E.
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mul8By8:
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push de
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ld l, 0
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ld d, l
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sla h
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jr nc, $ + 3
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ld l, e
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, hl
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jr nc, $ + 3
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add hl, hl
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jr nc, $ + 3
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add hl, de
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add hl, de
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pop de
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ret
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;; mul32By8 [Maths]
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;; Performs an unsigned multiplication of DEHL and A.
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;; Outputs:
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;; DEHL: product of DEHL and A
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mul32By8:
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push bc \ push ix
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ld ixl, 8
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push de
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push hl
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ld hl, 0
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ld d, h
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ld e, l
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mul32by8loop:
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add hl, hl
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rl e
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rl d
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rla
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jr nc, mul32by8noAdd
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pop bc
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add hl, bc
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ex (sp), hl
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push hl
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adc hl, de
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pop de
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ex de, hl
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ex (sp), hl
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push bc
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mul32by8noAdd:
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dec ixl
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jr nz, mul32by8loop
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pop bc
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pop bc
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pop ix \ pop bc
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ret
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