Instruction Set

INSTRUCTION_SET.js

// 0nnn - SYS addr
// 00E0 - CLS
// 00EE - RET
// 1nnn - JP addr
// 2nnn - CALL addr
// 3xkk - SE Vx, byte

const INSTRUCTION_SET = [
  {
    name: 'SYS',
    mask: 0xf000,
    pattern: 0x0000,
    arguments: [ { mask: 0x0fff, shift: 0, type: 'Address' } ],
  },
  {
    name: 'CLS',
    mask: 0x00f0,
    pattern: 0x00e0,
    arguments: [],
  },
  {
    name: 'RET',
    mask: 0x00ff,
    pattern: 0x00ee,
    arguments: [],
  },
  {
    name: 'JP',
    mask: 0xf000,
    pattern: 0x1000,
    arguments: [ { mask: 0x0fff, shift: 0, type: 'Address' } ],
  },
  {
    name: 'CALL',
    mask: 0xf000,
    pattern: 0x2000,
    arguments: [ { mask: 0x0fff, shift: 0, type: 'Address' } ],
  },
  {
    name: 'SE',
    mask: 0xf000,
    pattern: 0x3000,
    arguments: [
      { mask: 0x0f00, shift: 8, type: 'Register' },
      { mask: 0x00ff, shift: 0, type: 'Constant' },
    ],
  },
]

function findInstruction(opcode) {
  let match = INSTRUCTION_SET.filter(
    instruction => (opcode & instruction.mask) === instruction.pattern
  )

  return match[0]
}

let opcode = 0x1fff

console.log(findInstruction(opcode))