mirror of
https://github.com/MoleskiCoder/EightBit.git
synced 2024-09-01 00:28:55 +00:00
196 lines
5.8 KiB
C++
196 lines
5.8 KiB
C++
#pragma once
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#include <cstdint>
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#include <utility>
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#include <EightBitCompilerDefinitions.h>
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#include <LittleEndianProcessor.h>
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#include <Register.h>
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#include <Signal.h>
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#include <EventArgs.h>
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namespace EightBit {
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class Bus;
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class MOS6502 : public LittleEndianProcessor {
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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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int execute() final;
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[[nodiscard]] int step() final;
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[[nodiscard]] constexpr auto& X() noexcept { return x; }
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[[nodiscard]] constexpr auto& Y() noexcept { return y; }
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[[nodiscard]] constexpr auto& A() noexcept { return a; }
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[[nodiscard]] constexpr auto& S() noexcept { return s; }
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[[nodiscard]] constexpr auto& P() noexcept { return p; }
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[[nodiscard]] constexpr const auto& P() const noexcept { return p; }
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DECLARE_PIN_INPUT(NMI)
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DECLARE_PIN_INPUT(SO)
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DECLARE_PIN_OUTPUT(SYNC)
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DECLARE_PIN_INPUT(RDY)
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DECLARE_PIN_OUTPUT(RW)
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protected:
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void handleRESET() final;
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void handleINT() final;
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void busWrite() final;
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[[nodiscard]] uint8_t busRead() final;
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[[nodiscard]] virtual uint8_t sub(uint8_t operand, uint8_t data, int borrow = 0) noexcept;
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[[nodiscard]] uint8_t sbc(uint8_t operand, uint8_t data) noexcept;
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[[nodiscard]] uint8_t sub_b(uint8_t operand, uint8_t data, int borrow) noexcept;
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[[nodiscard]] uint8_t sub_d(uint8_t operand, uint8_t data, int borrow) noexcept;
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[[nodiscard]] virtual uint8_t add(uint8_t operand, uint8_t data, int carry = 0) noexcept;
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[[nodiscard]] uint8_t adc(uint8_t operand, uint8_t data) noexcept;
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[[nodiscard]] uint8_t add_b(uint8_t operand, uint8_t data, int carry) noexcept;
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[[nodiscard]] uint8_t add_d(uint8_t operand, uint8_t data, int carry) noexcept;
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private:
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const uint8_t IRQvector = 0xfe; // IRQ vector
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const uint8_t RSTvector = 0xfc; // RST vector
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const uint8_t NMIvector = 0xfa; // NMI vector
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void handleNMI();
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void handleSO();
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void interrupt();
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void push(uint8_t value) final;
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[[nodiscard]] uint8_t pop() final;
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// Dummy stack push, used during RESET
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void dummyPush(uint8_t value);
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// Addressing modes
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[[nodiscard]] register16_t Address_Absolute();
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[[nodiscard]] uint8_t Address_ZeroPage();
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[[nodiscard]] register16_t Address_ZeroPageIndirect();
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[[nodiscard]] register16_t Address_Indirect();
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[[nodiscard]] uint8_t Address_ZeroPageX();
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[[nodiscard]] uint8_t Address_ZeroPageY();
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[[nodiscard]] std::pair<register16_t, uint8_t> Address_AbsoluteX();
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[[nodiscard]] std::pair<register16_t, uint8_t> Address_AbsoluteY();
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[[nodiscard]] register16_t Address_IndexedIndirectX();
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[[nodiscard]] std::pair<register16_t, uint8_t> Address_IndirectIndexedY();
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[[nodiscard]] register16_t Address_relative_byte();
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// Addressing modes, read
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enum class PageCrossingBehavior { AlwaysReadTwice, MaybeReadTwice };
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uint8_t AM_Immediate();
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uint8_t AM_Absolute();
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uint8_t AM_ZeroPage();
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uint8_t AM_AbsoluteX(PageCrossingBehavior behaviour = PageCrossingBehavior::MaybeReadTwice);
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uint8_t AM_AbsoluteY();
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uint8_t AM_ZeroPageX();
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uint8_t AM_ZeroPageY();
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uint8_t AM_IndexedIndirectX();
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uint8_t AM_IndirectIndexedY();
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// Flag adjustment
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void adjustZero(const uint8_t datum) noexcept { P() = clearBit(P(), ZF, datum); }
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void adjustNegative(const uint8_t datum) noexcept { P() = setBit(P(), NF, datum & NF); }
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void adjustNZ(const uint8_t datum) noexcept {
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adjustZero(datum);
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adjustNegative(datum);
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}
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// Flag checking
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[[nodiscard]] auto interruptMasked() const noexcept { return P() & IF; }
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[[nodiscard]] auto decimal() const noexcept { return P() & DF; }
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[[nodiscard]] auto negative() const noexcept { return P() & NF; }
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[[nodiscard]] auto zero() const noexcept { return P() & ZF; }
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[[nodiscard]] auto overflow() const noexcept { return P() & VF; }
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[[nodiscard]] auto carry() const noexcept { return P() & CF; }
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// Miscellaneous
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void branch(int condition);
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[[nodiscard]] auto through(const uint8_t data) noexcept {
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adjustNZ(data);
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return data;
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}
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void memoryReadModifyWrite(const uint8_t data) {
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// The read will have already taken place...
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memoryWrite();
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memoryWrite(data);
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}
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// Instruction implementations
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[[nodiscard]] uint8_t andr(uint8_t operand, uint8_t data) noexcept;
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[[nodiscard]] uint8_t asl(uint8_t value) noexcept;
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void bit(uint8_t operand, uint8_t data) noexcept;
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void cmp(uint8_t first, uint8_t second) noexcept;
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[[nodiscard]] uint8_t dec(uint8_t value) noexcept;
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[[nodiscard]] uint8_t eorr(uint8_t operand, uint8_t data) noexcept;
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[[nodiscard]] uint8_t inc(uint8_t value) noexcept;
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void jsr();
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[[nodiscard]] uint8_t lsr(uint8_t value) noexcept;
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[[nodiscard]] uint8_t orr(uint8_t operand, uint8_t data) noexcept;
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void php();
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void plp();
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[[nodiscard]] uint8_t rol(uint8_t operand) noexcept;
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[[nodiscard]] uint8_t ror(uint8_t operand) noexcept;
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void rti();
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void rts();
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// Undocumented compound instructions
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void anc(uint8_t value) noexcept;
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void arr(uint8_t value) noexcept;
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void asr(uint8_t value) noexcept;
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void axs(uint8_t value) noexcept;
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void dcp(uint8_t value);
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void isb(uint8_t value);
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void rla(uint8_t value);
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void rra(uint8_t value);
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void slo(uint8_t value);
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void sre(uint8_t value);
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// Complicated addressing mode implementations
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void sta_AbsoluteX();
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void sta_AbsoluteY();
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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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register16_t m_intermediate;
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bool m_handlingRESET = false;
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bool m_handlingNMI = false;
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bool m_handlingINT = false;
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};
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} |