Add CPX, CPY, DEX, DEY, XCE, Emulation Mode
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scawful
@@ -334,23 +334,23 @@ void CPU::ExecuteInstruction(uint8_t opcode) {
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break;
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case 0xE0: // CPX Immediate
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// CPX();
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CPX(Immediate());
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break;
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case 0xE4: // CPX Direct Page
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// CPX();
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break;
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case 0xEC: // CPX Absolute
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// CPX();
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CPX(Absolute());
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break;
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case 0xC0: // CPY Immediate
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// CPY();
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CPY(Immediate());
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break;
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case 0xC4: // CPY Direct Page
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// CPY();
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break;
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case 0xCC: // CPY Absolute
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// CPY();
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CPY(Absolute());
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break;
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case 0x3A: // DEC Accumulator
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@@ -370,11 +370,11 @@ void CPU::ExecuteInstruction(uint8_t opcode) {
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break;
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case 0xCA: // DEX Decrement X register
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// DEX();
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DEX();
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break;
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case 0x88: // DEY Decrement Y register
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// DEY();
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DEY();
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break;
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case 0x41: // EOR DP Indexed Indirect, X
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@@ -951,7 +951,7 @@ void CPU::ExecuteInstruction(uint8_t opcode) {
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break;
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case 0xFB: // XCE
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// XCE();
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XCE();
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break;
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default:
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std::cerr << "Unknown instruction: " << std::hex
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@@ -962,7 +962,7 @@ void CPU::ExecuteInstruction(uint8_t opcode) {
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void CPU::ADC(uint8_t operand) {
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auto C = GetCarryFlag();
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if (GetAccumulatorSize()) { // 8-bit mode
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if (!E) { // 8-bit mode
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uint16_t result = (A & 0xFF) + (operand & 0xFF); // + (C ? 1 : 0);
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SetCarryFlag(!(result > 0xFF)); // Update the carry flag
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@@ -997,7 +997,7 @@ void CPU::ADC(uint8_t operand) {
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void CPU::AND(uint16_t address) {
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uint8_t operand;
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if (GetAccumulatorSize() == 0) { // 16-bit mode
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if (E == 0) { // 16-bit mode
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uint16_t operand16 = memory.ReadWord(address);
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A &= operand16;
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SetZeroFlag(A == 0);
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@@ -242,14 +242,14 @@ class CPU : public Memory {
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// ==========================================================================
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// Registers
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uint8_t A = 0; // Accumulator
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uint8_t X = 0; // X index register
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uint8_t Y = 0; // Y index register
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// uint8_t SP = 0; // Stack Pointer
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uint16_t DB = 0; // Data Bank register
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uint8_t A = 0; // Accumulator
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uint8_t X = 0; // X index register
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uint8_t Y = 0; // Y index register
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uint16_t D = 0; // Direct Page register
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uint16_t DB = 0; // Data Bank register
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uint16_t PB = 0; // Program Bank register
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uint16_t PC = 0; // Program Counter
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uint8_t E = 1; // Emulation mode flag
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uint8_t status; // Processor Status (P)
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// Mnemonic Value Binary Description
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@@ -312,12 +312,7 @@ class CPU : public Memory {
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// CPX: Compare X register
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// CPY: Compare Y register
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// DEC: Decrement
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// DEX: Decrement X register
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// DEY: Decrement Y register
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// EOR: Exclusive OR
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// INC: Increment
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// INX: Increment X register
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// INY: Increment Y register
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// JMP: Jump
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// JML: Jump long
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// JSR: Jump to subroutine
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@@ -333,19 +328,6 @@ class CPU : public Memory {
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// PEA: Push effective address
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// PEI: Push effective indirect address
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// PER: Push effective PC-relative address
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// PHA: Push accumulator
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// PHB: Push data bank register
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// PHD: Push direct page register
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// PHK: Push program bank register
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// PHP: Push processor status register
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// PHX: Push X register
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// PHY: Push Y register
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// PLA: Pull accumulator
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// PLB: Pull data bank register
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// PLD: Pull direct page register
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// PLP: Pull processor status register
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// PLX: Pull X register
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// PLY: Pull Y register
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// ROL: Rotate left
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// ROR: Rotate right
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// RTI: Return from interrupt
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@@ -390,16 +372,86 @@ class CPU : public Memory {
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PC++;
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}
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// SEC: Set carry flag
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void SEC() { status |= 0x01; }
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// CLC: Clear carry flag
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void CLC() { status &= ~0x01; }
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// CLD: Clear decimal mode
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void CLD() { status &= ~0x08; }
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// CLI: Clear interrupt disable flag
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void CLI() { status &= ~0x04; }
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// CLV: Clear overflow flag
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void CLV() { status &= ~0x40; }
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bool emulation_mode = false;
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void CPX(uint16_t address) {
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uint16_t memory_value =
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E ? memory.ReadByte(address) : memory.ReadWord(address);
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compare(X, memory_value);
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}
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void CPY(uint16_t address) {
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uint16_t memory_value =
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E ? memory.ReadByte(address) : memory.ReadWord(address);
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compare(Y, memory_value);
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}
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// DEX: Decrement X register
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void DEX() {
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X--;
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SetZeroFlag(X == 0);
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SetNegativeFlag(X & 0x80);
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}
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// DEY: Decrement Y register
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void DEY() {
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Y--;
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SetZeroFlag(Y == 0);
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SetNegativeFlag(Y & 0x80);
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}
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// INX: Increment X register
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void INX() {
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X++;
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SetNegativeFlag(X & 0x80);
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SetZeroFlag(X == 0);
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}
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// INY: Increment Y register
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void INY() {
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Y++;
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SetNegativeFlag(Y & 0x80);
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SetZeroFlag(Y == 0);
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}
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// INC: Increment memory
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void INC(uint16_t address) {
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if (GetAccumulatorSize()) {
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uint8_t value = ReadByte(address);
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value++;
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if (value == static_cast<uint8_t>(0x100)) {
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value = 0x00; // Wrap around in 8-bit mode
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}
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WriteByte(address, value);
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SetNegativeFlag(value & 0x80);
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SetZeroFlag(value == 0);
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} else {
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uint16_t value = ReadWord(address);
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value++;
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if (value == static_cast<uint16_t>(0x10000)) {
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value = 0x0000; // Wrap around in 16-bit mode
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}
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WriteByte(address, value);
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SetNegativeFlag(value & 0x80);
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SetZeroFlag(value == 0);
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}
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}
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// Push Accumulator on Stack
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void PHA() { memory.PushByte(A); }
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@@ -535,19 +587,22 @@ class CPU : public Memory {
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SetNegativeFlag(A & 0x80);
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}
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void INX() {
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X++;
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SetZeroFlag(X == 0);
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SetNegativeFlag(X & 0x80);
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}
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void INY() {
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Y++;
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SetZeroFlag(Y == 0);
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SetNegativeFlag(Y & 0x80);
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// XCE: Exchange Carry and Emulation Flags
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void XCE() {
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uint8_t carry = status & 0x01;
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status &= ~0x01;
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status |= E;
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E = carry;
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}
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private:
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void compare(uint16_t register_value, uint16_t memory_value) {
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uint16_t result = register_value - memory_value;
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SetNegativeFlag(result & (E ? 0x8000 : 0x80)); // Negative flag
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SetZeroFlag(result == 0); // Zero flag
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SetCarryFlag(register_value >= 0); // Carry flag
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}
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// Helper function to set or clear a specific flag bit
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void SetFlag(uint8_t mask, bool set) {
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if (set) {
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@@ -74,8 +74,8 @@ class MemoryImpl : public Memory {
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}
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void WriteByte(uint32_t address, uint8_t value) override {
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uint32_t mapped_address = GetMappedAddress(address);
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memory_.at(mapped_address) = value;
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// uint32_t mapped_address = GetMappedAddress(address);
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memory_[address] = value;
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}
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void WriteWord(uint32_t address, uint16_t value) override {
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uint32_t mapped_address = GetMappedAddress(address);
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