mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-12-26 03:32:51 +00:00
328 lines
6.4 KiB
C++
328 lines
6.4 KiB
C++
#pragma once
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#include <cstdint>
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#include <string>
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#include <array>
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#include <functional>
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#include <cassert>
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#include <Bus.h>
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#include <Processor.h>
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#include <Signal.h>
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namespace EightBit {
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class MOS6502 : public Processor {
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public:
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enum StatusBits {
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NF = Bit7, // Negative
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VF = Bit6, // Overflow
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RF = Bit5, // reserved
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BF = Bit4, // Brk
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DF = Bit3, // D (use BCD for arithmetic)
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IF = Bit2, // I (IRQ disable)
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ZF = Bit1, // Zero
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CF = Bit0, // Carry
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};
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MOS6502(Bus& bus);
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Signal<MOS6502> ExecutingInstruction;
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Signal<MOS6502> ExecutedInstruction;
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virtual int execute(uint8_t opcode) final;
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virtual int step() final;
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virtual void powerOn() override;
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uint8_t& X() { return x; }
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uint8_t& Y() { return y; }
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uint8_t& A() { return a; }
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uint8_t& S() { return s; }
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uint8_t& P() { return p; }
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PinLevel& SO() { return m_soLine; } // In
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protected:
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virtual void reset() final;
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virtual uint8_t SUB(uint8_t operand, uint8_t data, int borrow = 0);
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uint8_t SBC(uint8_t operand, uint8_t data);
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uint8_t SUB_b(uint8_t operand, uint8_t data, int borrow);
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uint8_t SUB_d(uint8_t operand, uint8_t data, int borrow);
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virtual uint8_t ADD(uint8_t operand, uint8_t data, int carry = 0);
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uint8_t ADC(uint8_t operand, uint8_t data);
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uint8_t ADD_b(uint8_t operand, uint8_t data, int carry);
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uint8_t ADD_d(uint8_t operand, uint8_t data, int carry);
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private:
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void interrupt(uint8_t vector);
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void adjustZero(uint8_t datum) { clearFlag(P(), ZF, datum); }
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void adjustNegative(uint8_t datum) { setFlag(P(), NF, datum & NF); }
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void adjustNZ(uint8_t datum) {
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adjustZero(datum);
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adjustNegative(datum);
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}
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void getWordPaged(uint8_t page, uint8_t offset, register16_t& output);
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uint8_t getBytePaged(uint8_t page, uint8_t offset);
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void setBytePaged(uint8_t page, uint8_t offset, uint8_t value);
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virtual void push(uint8_t value) final;
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virtual uint8_t pop() final;
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// Address resolution
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void Address_Absolute() {
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fetchWord();
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}
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void Address_ZeroPage() {
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MEMPTR().low = fetchByte();
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MEMPTR().high = 0;
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}
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void Address_ZeroPageIndirect() {
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Address_ZeroPage();
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getWordPaged(0, MEMPTR().low, MEMPTR());
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}
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void Address_Indirect() {
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Address_Absolute();
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getWordPaged(MEMPTR().high, MEMPTR().low, MEMPTR());
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}
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void Address_ZeroPageX() {
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Address_ZeroPage();
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MEMPTR().low += X();
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}
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void Address_ZeroPageY() {
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Address_ZeroPage();
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MEMPTR().low += Y();
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}
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bool Address_AbsoluteX() {
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Address_Absolute();
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const auto page = MEMPTR().high;
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MEMPTR().word += X();
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return MEMPTR().high != page;
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}
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bool Address_AbsoluteY() {
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Address_Absolute();
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const auto page = MEMPTR().high;
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MEMPTR().word += Y();
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return MEMPTR().high != page;
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}
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void Address_IndexedIndirectX() {
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Address_ZeroPageX();
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getWordPaged(0, MEMPTR().low, MEMPTR());
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}
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bool Address_IndirectIndexedY() {
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Address_ZeroPageIndirect();
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const auto page = MEMPTR().high;
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MEMPTR().word += Y();
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return MEMPTR().high != page;
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}
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// Addressing modes, read
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uint8_t AM_Immediate() {
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return fetchByte();
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}
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uint8_t AM_Absolute() {
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Address_Absolute();
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return getByte(MEMPTR());
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}
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uint8_t AM_ZeroPage() {
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Address_ZeroPage();
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return getByte(MEMPTR());
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}
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uint8_t AM_AbsoluteX() {
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if (UNLIKELY(Address_AbsoluteX()))
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addCycle();
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return getByte(MEMPTR());
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}
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uint8_t AM_AbsoluteY() {
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if (UNLIKELY(Address_AbsoluteY()))
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addCycle();
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return getByte(MEMPTR());
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}
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uint8_t AM_ZeroPageX() {
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Address_ZeroPageX();
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return getByte(MEMPTR());
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}
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uint8_t AM_ZeroPageY() {
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Address_ZeroPageY();
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return getByte(MEMPTR());
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}
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uint8_t AM_IndexedIndirectX() {
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Address_IndexedIndirectX();
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return getByte(MEMPTR());
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}
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uint8_t AM_IndirectIndexedY() {
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if (UNLIKELY(Address_IndirectIndexedY()))
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addCycle();
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return getByte(MEMPTR());
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}
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// Addressing modes, write
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void AM_Absolute(uint8_t value) {
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Address_Absolute();
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setByte(MEMPTR(), value);
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}
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void AM_ZeroPage(uint8_t value) {
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Address_ZeroPage();
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setByte(MEMPTR(), value);
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}
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void AM_AbsoluteX(uint8_t value) {
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Address_AbsoluteX();
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setByte(MEMPTR(), value);
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}
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void AM_AbsoluteY(uint8_t value) {
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Address_AbsoluteY();
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setByte(MEMPTR(), value);
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}
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void AM_ZeroPageX(uint8_t value) {
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Address_ZeroPageX();
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setByte(MEMPTR(), value);
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}
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void AM_ZeroPageY(uint8_t value) {
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Address_ZeroPageY();
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setByte(MEMPTR(), value);
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}
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void AM_IndexedIndirectX(uint8_t value) {
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Address_IndexedIndirectX();
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setByte(MEMPTR(), value);
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}
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void AM_IndirectIndexedY(uint8_t value) {
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Address_IndirectIndexedY();
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setByte(MEMPTR(), value);
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}
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// Operations
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void DCP(uint8_t value) {
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setByte(--value);
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CMP(A(), value);
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}
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void ISB(uint8_t value) {
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setByte(++value);
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A() = SBC(A(), value);
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}
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void SLO(uint8_t value) {
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const auto result = ASL(value);
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setByte(result);
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ORA(result);
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}
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void SRE(uint8_t value) {
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const auto result = LSR(value);
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setByte(result);
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EORA(result);
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}
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void RLA(uint8_t value) {
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const auto result = ROL(value);
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setByte(result);
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ANDA(result);
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}
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void RRA(uint8_t value) {
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const auto result = ROR(value);
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setByte(result);
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A() = ADC(A(), result);
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}
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void LAX(uint8_t value) {
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adjustNZ(X() = A() = value);
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}
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//
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uint8_t DEC(uint8_t value) {
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const auto result = --value;
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adjustNZ(result);
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return result;
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}
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uint8_t INC(uint8_t value) {
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const auto result = ++value;
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adjustNZ(result);
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return result;
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}
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void ORA(uint8_t value) {
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adjustNZ(A() |= value);
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}
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void ANDA(uint8_t value) {
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adjustNZ(A() &= value);
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}
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void EORA(uint8_t value) {
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adjustNZ(A() ^= value);
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}
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uint8_t ROR(uint8_t value);
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uint8_t LSR(uint8_t value);
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void BIT(uint8_t data);
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uint8_t ROL(uint8_t value);
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uint8_t ASL(uint8_t value);
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void CMP(uint8_t first, uint8_t second);
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void Branch(int8_t displacement);
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void Branch(bool flag);
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void PHP();
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void PLP();
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void JSR_abs();
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void RTI();
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void RTS();
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void JMP_abs();
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void JMP_ind();
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void BRK();
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// All interrupt vectors are on the 0xFF page
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const uint8_t IRQvector = 0xfe;
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const uint8_t RSTvector = 0xfc;
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const uint8_t NMIvector = 0xfa;
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uint8_t x = 0; // index register X
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uint8_t y = 0; // index register Y
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uint8_t a = 0; // accumulator
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uint8_t s = 0; // stack pointer
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uint8_t p = 0; // processor status
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PinLevel m_soLine = Low;
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};
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} |