284 lines
9.6 KiB
C++
284 lines
9.6 KiB
C++
//
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// Decoder.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 15/01/21.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "Decoder.hpp"
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#include <algorithm>
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namespace InstructionSet {
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namespace M50740 {
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Instruction Decoder::instrucion_for_opcode(const uint8_t opcode) {
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switch(opcode) {
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default: return Instruction(opcode);
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#define Map(opcode, operation, addressing_mode) \
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case opcode: return Instruction(Operation::operation, AddressingMode::addressing_mode, opcode);
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/* 0x00 – 0x0f */
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Map(0x00, BRK, Implied); Map(0x01, ORA, XIndirect);
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Map(0x02, JSR, ZeroPageIndirect); Map(0x03, BBS0, AccumulatorRelative);
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Map(0x05, ORA, ZeroPage);
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Map(0x06, ASL, ZeroPage); Map(0x07, BBS0, ZeroPageRelative);
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Map(0x08, PHP, Implied); Map(0x09, ORA, Immediate);
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Map(0x0a, ASL, Accumulator); Map(0x0b, SEB0, Accumulator);
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Map(0x0d, ORA, Absolute);
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Map(0x0e, ASL, Absolute); Map(0x0f, SEB0, ZeroPage);
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/* 0x10 – 0x1f */
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Map(0x10, BPL, Relative); Map(0x11, ORA, IndirectY);
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Map(0x12, CLT, Implied); Map(0x13, BBC0, AccumulatorRelative);
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Map(0x15, ORA, ZeroPageX);
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Map(0x16, ASL, ZeroPageX); Map(0x17, BBC0, ZeroPageRelative);
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Map(0x18, CLC, Implied); Map(0x19, ORA, AbsoluteY);
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Map(0x1a, DEC, Accumulator); Map(0x1b, CLB0, Accumulator);
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Map(0x1d, ORA, AbsoluteX);
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Map(0x1e, ASL, AbsoluteX); Map(0x1f, CLB0, ZeroPage);
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/* 0x20 – 0x2f */
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Map(0x20, JSR, Absolute); Map(0x21, AND, XIndirect);
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Map(0x22, JSR, SpecialPage); Map(0x23, BBS1, AccumulatorRelative);
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Map(0x24, BIT, ZeroPage); Map(0x25, AND, ZeroPage);
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Map(0x26, ROL, ZeroPage); Map(0x27, BBS1, ZeroPageRelative);
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Map(0x28, PLP, Implied); Map(0x29, AND, Immediate);
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Map(0x2a, ROL, Accumulator); Map(0x2b, SEB1, Accumulator);
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Map(0x2c, BIT, Absolute); Map(0x2d, AND, Absolute);
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Map(0x2e, ROL, Absolute); Map(0x2f, SEB1, ZeroPage);
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/* 0x30 – 0x3f */
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Map(0x30, BMI, Relative); Map(0x31, AND, IndirectY);
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Map(0x32, SET, Implied); Map(0x33, BBC1, AccumulatorRelative);
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Map(0x35, AND, ZeroPageX);
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Map(0x36, ROL, ZeroPageX); Map(0x37, BBC1, ZeroPageRelative);
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Map(0x38, SEC, Implied); Map(0x39, AND, AbsoluteY);
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Map(0x3a, INC, Accumulator); Map(0x3b, CLB1, Accumulator);
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Map(0x3c, LDM, ImmediateZeroPage); Map(0x3d, AND, AbsoluteX);
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Map(0x3e, ROL, AbsoluteX); Map(0x3f, CLB1, ZeroPage);
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/* 0x40 – 0x4f */
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Map(0x40, RTI, Implied); Map(0x41, EOR, XIndirect);
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Map(0x42, STP, Implied); Map(0x43, BBS2, AccumulatorRelative);
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Map(0x44, COM, ZeroPage); Map(0x45, EOR, ZeroPage);
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Map(0x46, LSR, ZeroPage); Map(0x47, BBS2, ZeroPageRelative);
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Map(0x48, PHA, Implied); Map(0x49, EOR, Immediate);
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Map(0x4a, LSR, Accumulator); Map(0x4b, SEB2, Accumulator);
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Map(0x4c, JMP, Absolute); Map(0x4d, EOR, Absolute);
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Map(0x4e, LSR, Absolute); Map(0x4f, SEB2, ZeroPage);
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/* 0x50 – 0x5f */
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Map(0x50, BVC, Relative); Map(0x51, EOR, IndirectY);
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Map(0x53, BBC2, AccumulatorRelative);
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Map(0x55, EOR, ZeroPageX);
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Map(0x56, LSR, ZeroPageX); Map(0x57, BBC2, ZeroPageRelative);
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Map(0x58, CLI, Implied); Map(0x59, EOR, AbsoluteY);
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Map(0x5b, CLB2, Accumulator);
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Map(0x5d, EOR, AbsoluteX);
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Map(0x5e, LSR, AbsoluteX); Map(0x5f, CLB2, ZeroPage);
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/* 0x60 – 0x6f */
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Map(0x60, RTS, Implied); Map(0x61, ADC, XIndirect);
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Map(0x63, BBS3, AccumulatorRelative);
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Map(0x64, TST, ZeroPage); Map(0x65, ADC, ZeroPage);
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Map(0x66, ROR, ZeroPage); Map(0x67, BBS3, ZeroPageRelative);
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Map(0x68, PLA, Implied); Map(0x69, ADC, Immediate);
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Map(0x6a, ROR, Accumulator); Map(0x6b, SEB3, Accumulator);
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Map(0x6c, JMP, AbsoluteIndirect); Map(0x6d, ADC, Absolute);
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Map(0x6e, ROR, Absolute); Map(0x6f, SEB3, ZeroPage);
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/* 0x70 – 0x7f */
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Map(0x70, BVS, Relative); Map(0x71, ADC, IndirectY);
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Map(0x73, BBC3, AccumulatorRelative);
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Map(0x75, ADC, ZeroPageX);
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Map(0x76, ROR, ZeroPageX); Map(0x77, BBC3, ZeroPageRelative);
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Map(0x78, SEI, Implied); Map(0x79, ADC, AbsoluteY);
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Map(0x7b, CLB3, Accumulator);
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Map(0x7d, ADC, AbsoluteX);
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Map(0x7e, ROR, AbsoluteX); Map(0x7f, CLB3, ZeroPage);
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/* 0x80 – 0x8f */
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Map(0x80, BRA, Relative); Map(0x81, STA, XIndirect);
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Map(0x82, RRF, ZeroPage); Map(0x83, BBS4, AccumulatorRelative);
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Map(0x84, STY, ZeroPage); Map(0x85, STA, ZeroPage);
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Map(0x86, STX, ZeroPage); Map(0x87, BBS4, ZeroPageRelative);
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Map(0x88, DEY, Implied);
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Map(0x8a, TXA, Implied); Map(0x8b, SEB4, Accumulator);
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Map(0x8c, STY, Absolute); Map(0x8d, STA, Absolute);
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Map(0x8e, STX, Absolute); Map(0x8f, SEB4, ZeroPage);
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/* 0x90 – 0x9f */
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Map(0x90, BCC, Relative); Map(0x91, STA, IndirectY);
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Map(0x93, BBC4, AccumulatorRelative);
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Map(0x94, STY, ZeroPageX); Map(0x95, STA, ZeroPageX);
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Map(0x96, STX, ZeroPageX); Map(0x97, BBC4, ZeroPageRelative);
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Map(0x98, TYA, Implied); Map(0x99, STA, AbsoluteY);
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Map(0x9a, TXS, Implied); Map(0x9b, CLB4, Accumulator);
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Map(0x9d, ADC, AbsoluteX);
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Map(0x9f, CLB4, ZeroPage);
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/* 0xa0 – 0xaf */
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Map(0xa0, LDY, Immediate); Map(0xa1, LDA, XIndirect);
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Map(0xa2, LDX, Immediate); Map(0xa3, BBS5, AccumulatorRelative);
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Map(0xa4, LDY, ZeroPage); Map(0xa5, LDA, ZeroPage);
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Map(0xa6, LDX, ZeroPage); Map(0xa7, BBS5, ZeroPageRelative);
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Map(0xa8, TAY, Implied); Map(0xa9, LDA, Immediate);
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Map(0xaa, TAX, Implied); Map(0xab, SEB5, Accumulator);
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Map(0xac, LDY, Absolute); Map(0xad, LDA, Absolute);
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Map(0xae, LDX, Absolute); Map(0xaf, SEB5, ZeroPage);
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/* 0xb0 – 0xbf */
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Map(0xb0, BCS, Relative); Map(0xb1, STA, IndirectY);
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Map(0xb2, JMP, ZeroPageIndirect); Map(0xb3, BBC5, AccumulatorRelative);
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Map(0xb4, LDY, ZeroPageX); Map(0xb5, LDA, ZeroPageX);
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Map(0xb6, LDX, ZeroPageY); Map(0xb7, BBC5, ZeroPageRelative);
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Map(0xb8, CLV, Implied); Map(0xb9, LDA, AbsoluteY);
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Map(0xba, TSX, Implied); Map(0xbb, CLB5, Accumulator);
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Map(0xbc, LDY, AbsoluteX); Map(0xbd, LDA, AbsoluteX);
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Map(0xbe, LDX, AbsoluteY); Map(0xbf, CLB5, ZeroPage);
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/* 0xc0 – 0xcf */
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Map(0xc0, CPY, Immediate); Map(0xc1, CMP, XIndirect);
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Map(0xc2, SLW, Implied); Map(0xc3, BBS6, AccumulatorRelative);
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Map(0xc4, CPY, ZeroPage); Map(0xc5, CMP, ZeroPage);
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Map(0xc6, DEC, ZeroPage); Map(0xc7, BBS6, ZeroPageRelative);
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Map(0xc8, INY, Implied); Map(0xc9, CMP, Immediate);
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Map(0xca, DEX, Implied); Map(0xcb, SEB6, Accumulator);
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Map(0xcc, CPY, Absolute); Map(0xcd, CMP, Absolute);
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Map(0xce, DEC, Absolute); Map(0xcf, SEB6, ZeroPage);
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/* 0xd0 – 0xdf */
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Map(0xd0, BNE, Relative); Map(0xd1, CMP, IndirectY);
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Map(0xd3, BBC6, AccumulatorRelative);
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Map(0xd5, CMP, ZeroPageX);
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Map(0xd6, DEC, ZeroPageX); Map(0xd7, BBC6, ZeroPageRelative);
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Map(0xd8, CLD, Implied); Map(0xd9, CMP, AbsoluteY);
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Map(0xdb, CLB6, Accumulator);
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Map(0xdd, CMP, AbsoluteX);
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Map(0xde, DEC, AbsoluteX); Map(0xdf, CLB6, ZeroPage);
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/* 0xe0 – 0xef */
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Map(0xe0, CPX, Immediate); Map(0xe1, SBC, XIndirect);
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Map(0xe2, FST, Implied); Map(0xe3, BBS7, AccumulatorRelative);
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Map(0xe4, CPX, ZeroPage); Map(0xe5, SBC, ZeroPage);
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Map(0xe6, INC, ZeroPage); Map(0xe7, BBS7, ZeroPageRelative);
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Map(0xe8, INX, Implied); Map(0xe9, SBC, Immediate);
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Map(0xea, NOP, Implied); Map(0xeb, SEB7, Accumulator);
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Map(0xec, CPX, Absolute); Map(0xed, SBC, Absolute);
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Map(0xee, INC, Absolute); Map(0xef, SEB7, ZeroPage);
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/* 0xf0 – 0xff */
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Map(0xf0, BEQ, Relative); Map(0xf1, SBC, IndirectY);
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Map(0xf3, BBC7, AccumulatorRelative);
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Map(0xf5, SBC, ZeroPageX);
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Map(0xf6, INC, ZeroPageX); Map(0xf7, BBC7, ZeroPageRelative);
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Map(0xf8, SED, Implied); Map(0xf9, SBC, AbsoluteY);
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Map(0xfb, CLB7, Accumulator);
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Map(0xfd, SBC, AbsoluteX);
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Map(0xfe, INC, AbsoluteX); Map(0xff, CLB7, ZeroPage);
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#undef Map
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}
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}
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std::pair<int, InstructionSet::M50740::Instruction> Decoder::decode(const uint8_t *source, const size_t length) {
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const uint8_t *const end = source + length;
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if(phase_ == Phase::Instruction && source != end) {
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const uint8_t instruction = *source;
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++source;
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++consumed_;
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// Determine the instruction in hand, and finish now if its undefined.
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instr_ = instrucion_for_opcode(instruction);
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if(instr_.operation == Operation::Invalid) {
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consumed_ = 0;
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return std::make_pair(1, instr_);
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}
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// Obtain an operand size and roll onto the correct phase.
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operand_size_ = size(instr_.addressing_mode);
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phase_ = operand_size_ ? Phase::AwaitingOperand : Phase::ReadyToPost;
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operand_bytes_ = 0;
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}
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if(phase_ == Phase::AwaitingOperand && source != end) {
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const int outstanding_bytes = operand_size_ - operand_bytes_;
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const int bytes_to_consume = std::min(int(end - source), outstanding_bytes);
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consumed_ += bytes_to_consume;
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/* source += bytes_to_consume; */
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operand_bytes_ += bytes_to_consume;
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if(operand_size_ == operand_bytes_) {
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phase_ = Phase::ReadyToPost;
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} else {
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return std::make_pair(-(operand_size_ - operand_bytes_), Instruction());
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}
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}
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if(phase_ == Phase::ReadyToPost) {
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const auto result = std::make_pair(consumed_, instr_);
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consumed_ = 0;
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phase_ = Phase::Instruction;
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return result;
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}
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// Decoding didn't complete, without it being clear how many more bytes are required.
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return std::make_pair(0, Instruction());
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}
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}
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}
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