Game Boy Opcodes

Game Boy CPU (Sharp LR35902) instruction set (opcodes)

The opcodes.json contains a JSON representation of the complete Sharp LR35902 instruction set. Inside the bin folder you will find the script used to generate the opcodes.json file from the pastraiser.com site.

Description of opcodes.json

The opcodes.json file includes some minor fixes in the opcode length and timings not present on the pastraiser.com site.

{
  "unprefixed": {
    "0xc0": {                 <-- Address
      "mnemonic": "SET",      <-- Instruction mnemonic
      "length": 2,            <-- Length in bytes
      "cycles": [             <-- Duration in cycles
        8
      ],
      "flags": [              <-- Flags affected
        "-",                  <-- Z - Zero Flag
        "-",                  <-- N - Subtract Flag
        "-",                  <-- H - Half Carry Flag
        "-"                   <-- C - Carry Flag
      ],
      "addr": "0xc0",         <-- Address
      "group": "control/misc" <-- Opcode group
      "operand1": "0",        <-- Operand 1
      "operand2": "B"         <-- Operand 2
    },
    ...
  },
  ...
}

Operation group table:

op group	description
x8/lsm	8-bit Load/Store/Move
x16/lsm	16-bit Load/Store/Move
x8/alu	8-bit Arithmetic Logic Unit
x16/alu	16-bit Arithmetic Logic Unit
x8/rsb	8-bit ???
control/br	branch
control/misc	misc

Reference documentation

http://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/lmmendes/game-boy-opcodes. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The code is available as open source under the terms of the MIT License.