// // Decoder.hpp // Clock Signal // // Created by Thomas Harte on 20/10/2025. // Copyright © 2025 Thomas Harte. All rights reserved. // #pragma once #include "Model.hpp" #include namespace CPU::MOS6502Mk2 { enum class Operation { BRK, NOP, JAM, ORA, AND, EOR, INS, ADC, SBC, CMP, CPX, CPY, BIT, BITNoNV, LDA, LDX, LDY, LAX, STA, STX, STY, STZ, SAX, SHA, SHX, SHY, SHS, ASL, ASO, ROL, RLA, LSR, LSE, ASR, ROR, RRA, CLC, CLI, CLV, CLD, SEC, SEI, SED, RMB, SMB, TRB, TSB, INC, DEC, INX, DEX, INY, DEY, INA, DEA, DCP, BPL, BMI, BVC, BVS, BCC, BCS, BNE, BEQ, BRA, BBRBBS, TXA, TYA, TXS, TAY, TAX, TSX, ARR, SBX, LXA, ANE, ANC, LAS, JSR, RTI, RTS, PHP, PLP, JMP, }; enum class AccessProgram { Implied, Immediate, Relative, Push, Pull, AbsoluteRead, AbsoluteModify, AbsoluteWrite, AbsoluteNOP, AbsoluteIndirect, AbsoluteXRead, AbsoluteXModify, AbsoluteXWrite, AbsoluteXNOP, AbsoluteYRead, AbsoluteYModify, AbsoluteYWrite, ZeroRead, ZeroModify, ZeroWrite, ZeroNOP, ZeroXRead, ZeroXModify, ZeroXWrite, ZeroXNOP, ZeroYRead, ZeroYModify, ZeroYWrite, ZeroIndirectRead, ZeroIndirectWrite, IndexedIndirectRead, IndexedIndirectModify, IndexedIndirectWrite, IndirectIndexedRead, IndirectIndexedModify, IndirectIndexedWrite, // Irregular. BRK, JSR, RTI, RTS, Max, }; struct Instruction { AccessProgram program; Operation operation; }; template struct Decoder; template struct Decoder> { static constexpr Instruction decode(const uint8_t opcode) { using enum AccessProgram; switch(opcode) { case 0x00: return {BRK, Operation::BRK}; case 0x20: return {JSR, Operation::JSR}; case 0x40: return {RTI, Operation::RTI}; case 0x60: return {RTS, Operation::RTS}; case 0x80: return {Immediate, Operation::NOP}; case 0xa0: return {Immediate, Operation::LDY}; case 0xc0: return {Immediate, Operation::CPY}; case 0xe0: return {Immediate, Operation::CPX}; case 0x01: return {IndirectIndexedRead, Operation::ORA}; case 0x21: return {IndirectIndexedRead, Operation::AND}; case 0x41: return {IndirectIndexedRead, Operation::EOR}; case 0x61: return {IndirectIndexedRead, Operation::ADC}; case 0x81: return {IndirectIndexedWrite, Operation::STA}; case 0xa1: return {IndirectIndexedRead, Operation::LDA}; case 0xc1: return {IndirectIndexedRead, Operation::CMP}; case 0xe1: return {IndirectIndexedRead, Operation::SBC}; case 0x02: return {Implied, Operation::JAM}; case 0x22: return {Implied, Operation::JAM}; case 0x42: return {Implied, Operation::JAM}; case 0x62: return {Implied, Operation::JAM}; case 0x82: return {Immediate, Operation::NOP}; case 0xa2: return {Immediate, Operation::LDX}; case 0xc2: return {Implied, Operation::NOP}; case 0xe2: return {Implied, Operation::NOP}; case 0x03: return {IndirectIndexedModify, Operation::ASO}; case 0x23: return {IndirectIndexedModify, Operation::RLA}; case 0x43: return {IndirectIndexedModify, Operation::LSE}; case 0x63: return {IndirectIndexedModify, Operation::RRA}; case 0x83: return {IndirectIndexedWrite, Operation::SAX}; case 0xa3: return {IndirectIndexedRead, Operation::LAX}; case 0xc3: return {IndirectIndexedWrite, Operation::DCP}; case 0xe3: return {IndirectIndexedWrite, Operation::INS}; case 0x04: return {ZeroNOP, Operation::NOP}; case 0x24: return {ZeroRead, Operation::BIT}; case 0x44: return {ZeroNOP, Operation::NOP}; case 0x64: return {ZeroNOP, Operation::NOP}; case 0x84: return {ZeroWrite, Operation::STY}; case 0xa4: return {ZeroRead, Operation::LDY}; case 0xc4: return {ZeroRead, Operation::CPY}; case 0xe4: return {ZeroRead, Operation::CPX}; case 0x05: return {ZeroRead, Operation::ORA}; case 0x25: return {ZeroRead, Operation::AND}; case 0x45: return {ZeroRead, Operation::EOR}; case 0x65: return {ZeroRead, Operation::ADC}; case 0x85: return {ZeroWrite, Operation::STA}; case 0xa5: return {ZeroRead, Operation::LDA}; case 0xc5: return {ZeroRead, Operation::CMP}; case 0xe5: return {ZeroRead, Operation::SBC}; case 0x06: return {ZeroModify, Operation::ASL}; case 0x26: return {ZeroModify, Operation::ROL}; case 0x46: return {ZeroModify, Operation::LSR}; case 0x66: return {ZeroModify, Operation::ROR}; case 0x86: return {ZeroWrite, Operation::STX}; case 0xa6: return {ZeroRead, Operation::LDX}; case 0xc6: return {ZeroModify, Operation::DEC}; case 0xe6: return {ZeroModify, Operation::INC}; case 0x07: return {ZeroModify, Operation::ASO}; case 0x27: return {ZeroModify, Operation::RLA}; case 0x47: return {ZeroModify, Operation::LSE}; case 0x67: return {ZeroModify, Operation::RRA}; case 0x87: return {ZeroWrite, Operation::SAX}; case 0xa7: return {ZeroRead, Operation::LDX}; case 0xc7: return {ZeroRead, Operation::LAX}; case 0xe7: return {ZeroModify, Operation::INS}; case 0x08: return {Push, Operation::PHP}; case 0x28: return {Pull, Operation::PLP}; case 0x48: return {Push, Operation::STA}; case 0x68: return {Pull, Operation::LDA}; case 0x88: return {Implied, Operation::DEY}; case 0xa8: return {Implied, Operation::TAY}; case 0xc8: return {Implied, Operation::INY}; case 0xe8: return {Implied, Operation::INX}; case 0x09: return {Immediate, Operation::ORA}; case 0x29: return {Immediate, Operation::AND}; case 0x49: return {Immediate, Operation::EOR}; case 0x69: return {Immediate, Operation::ADC}; case 0x89: return {Immediate, Operation::NOP}; case 0xa9: return {Immediate, Operation::LDA}; case 0xc9: return {Immediate, Operation::CMP}; case 0xe9: return {Immediate, Operation::SBC}; case 0x0a: return {Implied, Operation::ASL}; case 0x2a: return {Implied, Operation::ROL}; case 0x4a: return {Implied, Operation::LSR}; case 0x6a: return {Implied, Operation::ROR}; case 0x8a: return {Implied, Operation::TXA}; case 0xaa: return {Implied, Operation::TAX}; case 0xca: return {Implied, Operation::DEX}; case 0xea: return {Implied, Operation::NOP}; case 0x0b: return {Immediate, Operation::ANC}; case 0x2b: return {Immediate, Operation::ANC}; case 0x4b: return {Immediate, Operation::ASR}; case 0x6b: return {Immediate, Operation::ARR}; case 0x8b: return {Immediate, Operation::ANE}; case 0xab: return {Immediate, Operation::LXA}; case 0xcb: return {Immediate, Operation::SBX}; case 0xeb: return {Immediate, Operation::SBC}; case 0x0c: return {AbsoluteNOP, Operation::NOP}; case 0x2c: return {AbsoluteRead, Operation::BIT}; case 0x4c: return {AbsoluteNOP, Operation::JMP}; case 0x6c: return {AbsoluteIndirect, Operation::JMP}; case 0x8c: return {AbsoluteWrite, Operation::STY}; case 0xac: return {AbsoluteRead, Operation::LDY}; case 0xcc: return {AbsoluteRead, Operation::CPY}; case 0xec: return {AbsoluteRead, Operation::CPX}; case 0x0d: return {AbsoluteRead, Operation::ORA}; case 0x2d: return {AbsoluteRead, Operation::AND}; case 0x4d: return {AbsoluteRead, Operation::EOR}; case 0x6d: return {AbsoluteRead, Operation::ADC}; case 0x8d: return {AbsoluteWrite, Operation::STA}; case 0xad: return {AbsoluteRead, Operation::LDA}; case 0xcd: return {AbsoluteRead, Operation::CMP}; case 0xed: return {AbsoluteRead, Operation::SBC}; case 0x0f: return {AbsoluteModify, Operation::ASO}; case 0x2f: return {AbsoluteModify, Operation::RLA}; case 0x4f: return {AbsoluteModify, Operation::LSE}; case 0x6f: return {AbsoluteModify, Operation::RRA}; case 0x8f: return {AbsoluteWrite, Operation::SAX}; case 0xaf: return {AbsoluteRead, Operation::LAX}; case 0xcf: return {AbsoluteModify, Operation::DCP}; case 0xef: return {AbsoluteModify, Operation::INS}; case 0x10: return {Relative, Operation::BPL}; case 0x30: return {Relative, Operation::BMI}; case 0x50: return {Relative, Operation::BVC}; case 0x70: return {Relative, Operation::BVS}; case 0x90: return {Relative, Operation::BCC}; case 0xb0: return {Relative, Operation::BCS}; case 0xd0: return {Relative, Operation::BNE}; case 0xf0: return {Relative, Operation::BEQ}; case 0x11: return {IndirectIndexedRead, Operation::ORA}; case 0x31: return {IndirectIndexedRead, Operation::AND}; case 0x51: return {IndirectIndexedRead, Operation::EOR}; case 0x71: return {IndirectIndexedRead, Operation::ADC}; case 0x91: return {IndirectIndexedRead, Operation::STA}; case 0xb1: return {IndirectIndexedRead, Operation::LDA}; case 0xd1: return {IndirectIndexedRead, Operation::CMP}; case 0xf1: return {IndirectIndexedRead, Operation::SBC}; case 0x12: return {Implied, Operation::JAM}; case 0x32: return {Implied, Operation::JAM}; case 0x52: return {Implied, Operation::JAM}; case 0x72: return {Implied, Operation::JAM}; case 0x92: return {Implied, Operation::JAM}; case 0xb2: return {Implied, Operation::JAM}; case 0xd2: return {Implied, Operation::JAM}; case 0xf2: return {Implied, Operation::JAM}; case 0x13: return {IndirectIndexedModify, Operation::ASO}; case 0x33: return {IndirectIndexedModify, Operation::RLA}; case 0x53: return {IndirectIndexedModify, Operation::LSE}; case 0x73: return {IndirectIndexedModify, Operation::RRA}; case 0x93: return {IndirectIndexedWrite, Operation::SHA}; case 0xb3: return {IndirectIndexedRead, Operation::LAX}; case 0xd3: return {IndirectIndexedModify, Operation::DCP}; case 0xf3: return {IndirectIndexedModify, Operation::INS}; case 0x14: return {ZeroXNOP, Operation::NOP}; case 0x34: return {ZeroXNOP, Operation::NOP}; case 0x54: return {ZeroXNOP, Operation::NOP}; case 0x74: return {ZeroXNOP, Operation::NOP}; case 0x94: return {ZeroXWrite, Operation::STY}; case 0xb4: return {ZeroXRead, Operation::LDY}; case 0xd4: return {ZeroXNOP, Operation::NOP}; case 0xf4: return {ZeroXNOP, Operation::NOP}; case 0x15: return {ZeroXRead, Operation::ORA}; case 0x35: return {ZeroXRead, Operation::AND}; case 0x55: return {ZeroXRead, Operation::EOR}; case 0x75: return {ZeroXRead, Operation::ADC}; case 0x95: return {ZeroXWrite, Operation::STA}; case 0xb5: return {ZeroXRead, Operation::LDA}; case 0xd5: return {ZeroXRead, Operation::CMP}; case 0xf5: return {ZeroXRead, Operation::SBC}; case 0x16: return {ZeroXModify, Operation::ASL}; case 0x36: return {ZeroXModify, Operation::ROL}; case 0x56: return {ZeroXModify, Operation::LSR}; case 0x76: return {ZeroXModify, Operation::ROR}; case 0x96: return {ZeroYWrite, Operation::STX}; case 0xb6: return {ZeroYRead, Operation::LDX}; case 0xd6: return {ZeroXModify, Operation::DEC}; case 0xf6: return {ZeroXModify, Operation::INC}; case 0x17: return {ZeroXModify, Operation::ASO}; case 0x37: return {ZeroXModify, Operation::RLA}; case 0x57: return {ZeroXModify, Operation::LSE}; case 0x77: return {ZeroXModify, Operation::RRA}; case 0x97: return {ZeroYWrite, Operation::SAX}; case 0xb7: return {ZeroYRead, Operation::LAX}; case 0xd7: return {ZeroXModify, Operation::DCP}; case 0xf7: return {ZeroXModify, Operation::INS}; case 0x18: return {Implied, Operation::CLC}; case 0x38: return {Implied, Operation::SEC}; case 0x58: return {Implied, Operation::CLI}; case 0x78: return {Implied, Operation::SEI}; case 0x98: return {Implied, Operation::TYA}; case 0xb8: return {Implied, Operation::CLV}; case 0xd8: return {Implied, Operation::CLD}; case 0xf8: return {Implied, Operation::SED}; case 0x19: return {AbsoluteYRead, Operation::ORA}; case 0x39: return {AbsoluteYRead, Operation::AND}; case 0x59: return {AbsoluteYRead, Operation::EOR}; case 0x79: return {AbsoluteYRead, Operation::ADC}; case 0x99: return {AbsoluteYWrite, Operation::STA}; case 0xb9: return {AbsoluteYRead, Operation::LDA}; case 0xd9: return {AbsoluteYRead, Operation::CMP}; case 0xf9: return {AbsoluteYRead, Operation::SBC}; case 0x1a: return {Implied, Operation::NOP}; case 0x3a: return {Implied, Operation::NOP}; case 0x5a: return {Implied, Operation::NOP}; case 0x7a: return {Implied, Operation::NOP}; case 0x9a: return {Implied, Operation::TXS}; case 0xba: return {Implied, Operation::TSX}; case 0xda: return {Implied, Operation::NOP}; case 0xfa: return {Implied, Operation::NOP}; case 0x1b: return {AbsoluteYModify, Operation::ASO}; case 0x3b: return {AbsoluteYModify, Operation::RLA}; case 0x5b: return {AbsoluteYModify, Operation::LSE}; case 0x7b: return {AbsoluteYModify, Operation::RRA}; case 0x9b: return {AbsoluteYWrite, Operation::SHS}; case 0xbb: return {AbsoluteYRead, Operation::LAS}; case 0xdb: return {AbsoluteYModify, Operation::DCP}; case 0xfb: return {AbsoluteYModify, Operation::INS}; case 0x1c: return {AbsoluteXNOP, Operation::NOP}; case 0x3c: return {AbsoluteXNOP, Operation::NOP}; case 0x5c: return {AbsoluteXNOP, Operation::NOP}; case 0x7c: return {AbsoluteXNOP, Operation::NOP}; case 0x9c: return {AbsoluteXWrite, Operation::SHY}; case 0xbc: return {AbsoluteXRead, Operation::LDY}; case 0xdc: return {AbsoluteXNOP, Operation::NOP}; case 0xfc: return {AbsoluteXNOP, Operation::NOP}; case 0x1d: return {AbsoluteXRead, Operation::ORA}; case 0x3d: return {AbsoluteXRead, Operation::AND}; case 0x5d: return {AbsoluteXRead, Operation::EOR}; case 0x7d: return {AbsoluteXRead, Operation::ADC}; case 0x9d: return {AbsoluteXWrite, Operation::STA}; case 0xbd: return {AbsoluteXRead, Operation::LDA}; case 0xdd: return {AbsoluteXRead, Operation::CMP}; case 0xfd: return {AbsoluteXRead, Operation::SBC}; case 0x1e: return {AbsoluteXModify, Operation::ASL}; case 0x3e: return {AbsoluteXModify, Operation::ROL}; case 0x5e: return {AbsoluteXModify, Operation::LSR}; case 0x7e: return {AbsoluteXModify, Operation::ROR}; case 0x9e: return {AbsoluteYWrite, Operation::SHX}; case 0xbe: return {AbsoluteYRead, Operation::LDX}; case 0xde: return {AbsoluteXModify, Operation::DEC}; case 0xfe: return {AbsoluteXModify, Operation::INC}; case 0x1f: return {AbsoluteXModify, Operation::ASO}; case 0x3f: return {AbsoluteXModify, Operation::RLA}; case 0x5f: return {AbsoluteXModify, Operation::LSE}; case 0x7f: return {AbsoluteXModify, Operation::ADC}; case 0x9f: return {AbsoluteYWrite, Operation::SHA}; case 0xbf: return {AbsoluteYRead, Operation::LAX}; case 0xdf: return {AbsoluteXModify, Operation::DCP}; case 0xff: return {AbsoluteXModify, Operation::INS}; } __builtin_unreachable(); } }; }