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Arithmetic

ADC

Adds the value in reg8 and the carry flag to the value in a. Also includes 1R cycle if reg8 is (hl).

  • Opcode: 10001 reg8
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
    (hl) 110
  • Bytes: 1
  • Flags:
  • Cycles: 1F

Adds the immediate value imm8 and the carry flag to the value in a.

  • Opcode: 11001110 imm8
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds the value in reg24 and the carry flag to the value in hl.

  • Opcode: 11101101 01 reg24 1010
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds the value in reg8i and the carry flag to the value in a.

  • Opcode: regi 1000110 reg8i
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds the value pointed to by regi + ofs8 and the carry flag to the value in a.

  • Opcode: regi 10001110 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R

ADD

Adds the value in reg24 to the value in hl.

  • Opcode: 00 reg24 1001
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 1
  • Flags:
    • H: Set if carry from bit 11, reset otherwise
    • N: Reset
    • C: Affected as defined
  • Cycles: 1F

Adds the value in reg8 to the value in a. Also includes 1R cycle if reg8 is (hl).

  • Opcode: 10000 reg8
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
    (hl) 110
  • Bytes: 1
  • Flags:
  • Cycles: 1F

Adds the immediate value imm8 to the value in a.

  • Opcode: 11000110 imm8
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds the value in reg24 to the value in regi.

  • Opcode: regi 00 reg24 1001
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    bc 00
    de 01
    ix/iy 10
    sp 11
  • Bytes: 2
  • Flags:
    • H: Set if carry from bit 11, reset otherwise
    • N: Reset
    • C: Affected as defined
  • Cycles: 2F

Adds the value in reg8i to the value in a.

  • Opcode: regi 10000100 reg8i
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds the value pointed to by regi + ofs8 to the value in a.

  • Opcode: regi 10000110 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R

CP

Compares (via subtraction) the value in reg8 with the value in a. Also includes 1R cycle if reg8 is (hl).

  • Opcode: 10111 reg8
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
    (hl) 110
  • Bytes: 1
  • Flags:
  • Cycles: 1F + 1R

Compares (via subtraction) the immediate value imm8 with the value in a.

  • Opcode: 11111110 imm8
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Compares (via subtraction) the value in reg8i with the value in a.

  • Opcode: regi 1011110 reg8i
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Compares (via subtraction) the value pointed to by regi + ofs8 with the value in a.

  • Opcode: regi 10111110 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R

DAA

This instruction is meant to be used after an addition or subtraction instruction on binary-coded-decimal values, specifically add, adc, inc, sub, sbc, dec, or neg. Following one of these specific instructions, daa adjusts the value in a according to this table:

Operation C flag prior to DAA H flag prior to DAA Upper digit of a Lower digit of a Number added to a C flag after DAA H flag after DAA
ADD, ADC, or INC 0 0 0 - 9 0 - 9 00 0 0
0 0 0 - 8 A - F 06 0 1
0 1 0 - 9 0 - 3 06 0 0
0 0 A - F 0 - 9 60 1 0
0 0 9 - F A - F 66 1 1
0 1 A - F 0 - 3 66 1 0
1 0 0 - 2 0 - 9 60 1 0
1 0 0 - 2 A - F 66 1 1
1 1 0 - 3 0 - 3 66 1 0
SUB, SBC, DEC, or NEG 0 0 0 - 9 0 - 9 00 0 0
0 1 0 - 8 6 - F FA 0 0
1 0 7 - F 0 - 9 A0 1 0
1 1 6 - F 6 - F 9A 1 0
  • Opcode: 00100111
  • Bytes: 1
  • Flags:
    • S: Set if msb of the result is 1, reset otherwise
    • Z: Set if result is 0, reset otherwise
    • H: See above table
    • P/V: Detects parity
    • C: See above table
  • Cycles: 1F

DEC

Subtracts one from the value in reg24.

  • Opcode: 00 reg24 1011
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 1
  • Flags:
    • None
  • Cycles: 1F

Subtracts one from the value pointed to by hl.

  • Opcode: 00110101
  • Bytes: 1
  • Flags:
  • Cycles: 1F + 1R + 1W + 1

Subtracts one from the value in reg8.

  • Opcode: 00 reg8 101
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
  • Bytes: 1
  • Flags:
  • Cycles: 1F

Subtracts one from the value in regi.

  • Opcode: regi 00101011
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 2
  • Flags:
    • None
  • Cycles: 2F

Subtracts one from the value in reg8i.

  • Opcode: regi 0010 reg8i 101
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts one from the 8-bit value pointed to by regi + ofs8.

  • Opcode: regi 00110101 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R + 1W + 1

INC

Adds one to the value in reg24.

  • Opcode: 00 reg24 0011
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 1
  • Flags:
    • None
  • Cycles: 1F

Adds one to the 8-bit value pointed to by hl.

  • Opcode: 00110100
  • Bytes: 1
  • Flags:
  • Cycles: 1F + 1R + 1W + 1

Adds one to the value in reg8.

  • Opcode: 00 reg8 100
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
  • Bytes: 1
  • Flags:
  • Cycles: 1F

Adds one to the value in regi.

  • Opcode: regi 00100011
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 2
  • Flags:
    • None
  • Cycles: 2F

Adds one to the value in reg8i.

  • Opcode: regi 0010 reg8i 100
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Adds one to the 8-bit value pointed to by regi + ofs8.

  • Opcode: regi 00110100 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R + 1W + 1

MLT

Multiplies the low byte of reg24 by the high byte of reg24. The 16-bit result is stored back into the register pair.

  • Opcode: 11101101 01 reg24 1100
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 2
  • Flags:
    • None
  • Cycles: 2F + 4

NEG

Negates the value of a. The result is identical to subtracting the value in a from 0.

  • Opcode: 11101101 01000100
  • Bytes: 2
  • Flags:
  • Cycles: 2F

SBC

Subtracts the value in reg8 and the carry flag from the value in a. Also includes 1R cycle if reg8 is (hl).

  • Opcode: 10011 reg8
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
    (hl) 110
  • Bytes: 1
  • Flags:
  • Cycles: 1F

Subtracts the immediate value imm8 and the carry flag from the value in a.

  • Opcode: 11011110 imm8
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts the value in reg24 and the carry flag from the value in hl.

  • Opcode: 11101101 01 reg24 0010
    Register Bit Field
    bc 00
    de 01
    hl 10
    sp 11
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts the value in reg8i and the carry flag from the value in a.

  • Opcode: regi 1001110 reg8i
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts the value pointed to by regi + ofs8 and the carry flag from the value in a.

  • Opcode: regi 10011110 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R

SUB

Subtracts the value in reg8 from the value in a. Also includes 1R cycle if reg8 is (hl).

  • Opcode: 10010 reg8
    Register Bit Field
    a 111
    b 000
    c 001
    d 010
    e 011
    h 100
    l 101
    (hl) 110
  • Bytes: 1
  • Flags:
  • Cycles: 1F + 1R

Subtracts the immediate value imm8 from the value in a.

  • Opcode: 11010110 imm8
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts the value in reg8i from the value in a.

  • Opcode: regi 1001010 reg8i
    Index Bit Field
    ix 11011101
    iy 11111101
    Register Bit Field
    l 0
    h 1
  • Bytes: 2
  • Flags:
  • Cycles: 2F

Subtracts the value pointed to by regi + ofs8 from the value in a.

  • Opcode: regi 10010110 ofs8
    Index Bit Field
    ix 11011101
    iy 11111101
  • Bytes: 3
  • Flags:
  • Cycles: 3F + 1R