EightBit/M6502/inc/mos6502.h
Adrian Conlon 1212e8d4f0 Tidy some processor virtual specifications.
Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
2018-08-25 13:35:53 +01:00

338 lines
7.0 KiB
C++

#pragma once
#include <cstdint>
#include <string>
#include <array>
#include <functional>
#include <cassert>
#include <Bus.h>
#include <LittleEndianProcessor.h>
#include <Signal.h>
namespace EightBit {
class MOS6502 : public LittleEndianProcessor {
public:
enum StatusBits {
NF = Bit7, // Negative
VF = Bit6, // Overflow
RF = Bit5, // reserved
BF = Bit4, // Brk
DF = Bit3, // D (use BCD for arithmetic)
IF = Bit2, // I (IRQ disable)
ZF = Bit1, // Zero
CF = Bit0, // Carry
};
MOS6502(Bus& bus);
Signal<MOS6502> ExecutingInstruction;
Signal<MOS6502> ExecutedInstruction;
virtual int execute(uint8_t opcode) final;
virtual int step() final;
virtual void powerOn() final;
uint8_t& X() { return x; }
uint8_t& Y() { return y; }
uint8_t& A() { return a; }
uint8_t& S() { return s; }
uint8_t& P() { return p; }
PinLevel& NMI() { return m_nmiLine; } // In
PinLevel& SO() { return m_soLine; } // In
protected:
virtual void handleRESET() final;
virtual void handleIRQ() final;
virtual uint8_t SUB(uint8_t operand, uint8_t data, int borrow = 0);
uint8_t SBC(uint8_t operand, uint8_t data);
uint8_t SUB_b(uint8_t operand, uint8_t data, int borrow);
uint8_t SUB_d(uint8_t operand, uint8_t data, int borrow);
virtual uint8_t ADD(uint8_t operand, uint8_t data, int carry = 0);
uint8_t ADC(uint8_t operand, uint8_t data);
uint8_t ADD_b(uint8_t operand, uint8_t data, int carry);
uint8_t ADD_d(uint8_t operand, uint8_t data, int carry);
private:
void handleNMI();
void handleSO();
void handleHALT();
void interrupt(uint8_t vector);
void adjustZero(uint8_t datum) { clearFlag(P(), ZF, datum); }
void adjustNegative(uint8_t datum) { setFlag(P(), NF, datum & NF); }
void adjustNZ(uint8_t datum) {
adjustZero(datum);
adjustNegative(datum);
}
virtual void push(uint8_t value) final;
virtual uint8_t pop() final;
// Address resolution
register16_t Address_Absolute() {
return fetchWord();
}
uint8_t Address_ZeroPage() {
return fetchByte();
}
register16_t Address_ZeroPageIndirect() {
return getWordPaged(0, Address_ZeroPage());
}
register16_t Address_Indirect() {
const auto address = Address_Absolute();
return getWordPaged(address.high, address.low);
}
uint8_t Address_ZeroPageX() {
return Address_ZeroPage() + X();
}
uint8_t Address_ZeroPageY() {
return Address_ZeroPage() + Y();
}
std::tuple<register16_t, bool> Address_AbsoluteX() {
auto address = Address_Absolute();
const auto page = address.high;
address += X();
return std::tuple<register16_t, bool>(address, address.high != page);
}
std::tuple<register16_t, bool> Address_AbsoluteY() {
auto address = Address_Absolute();
const auto page = address.high;
address += Y();
return std::tuple<register16_t, bool>(address, address.high != page);
}
register16_t Address_IndexedIndirectX() {
return getWordPaged(0, Address_ZeroPageX());
}
std::tuple<register16_t, bool> Address_IndirectIndexedY() {
auto address = Address_ZeroPageIndirect();
const auto page = address.high;
address += Y();
return std::tuple<register16_t, bool>(address, address.high != page);
}
// Addressing modes, read
uint8_t AM_Immediate() {
return fetchByte();
}
uint8_t AM_Absolute() {
return BUS().read(Address_Absolute());
}
uint8_t AM_ZeroPage() {
return BUS().read(Address_ZeroPage());
}
uint8_t AM_AbsoluteX() {
const auto ap = Address_AbsoluteX();
if (UNLIKELY(std::get<1>(ap)))
addCycle();
return BUS().read(std::get<0>(ap));
}
uint8_t AM_AbsoluteY() {
const auto ap = Address_AbsoluteY();
if (UNLIKELY(std::get<1>(ap)))
addCycle();
return BUS().read(std::get<0>(ap));
}
uint8_t AM_ZeroPageX() {
return BUS().read(Address_ZeroPageX());
}
uint8_t AM_ZeroPageY() {
return BUS().read(Address_ZeroPageY());
}
uint8_t AM_IndexedIndirectX() {
return BUS().read(Address_IndexedIndirectX());
}
uint8_t AM_IndirectIndexedY() {
const auto ap = Address_IndirectIndexedY();
if (UNLIKELY(std::get<1>(ap)))
addCycle();
return BUS().read(std::get<0>(ap));
}
// Addressing modes, write
void AM_Absolute(uint8_t value) {
BUS().write(Address_Absolute(), value);
}
void AM_ZeroPage(uint8_t value) {
BUS().write(Address_ZeroPage(), value);
}
void AM_AbsoluteX(uint8_t value) {
BUS().write(std::get<0>(Address_AbsoluteX()), value);
}
void AM_AbsoluteY(uint8_t value) {
BUS().write(std::get<0>(Address_AbsoluteY()), value);
}
void AM_ZeroPageX(uint8_t value) {
BUS().write(Address_ZeroPageX(), value);
}
void AM_ZeroPageY(uint8_t value) {
BUS().write(Address_ZeroPageY(), value);
}
void AM_IndexedIndirectX(uint8_t value) {
BUS().write(Address_IndexedIndirectX(), value);
}
void AM_IndirectIndexedY(uint8_t value) {
BUS().write(std::get<0>(Address_IndirectIndexedY()), value);
}
// Operations
void DCP(uint8_t value) {
BUS().write(--value);
CMP(A(), value);
}
void ISB(uint8_t value) {
BUS().write(++value);
A() = SBC(A(), value);
}
void SLO(uint8_t value) {
const auto result = ASL(value);
BUS().write(result);
ORA(result);
}
void SRE(uint8_t value) {
const auto result = LSR(value);
BUS().write(result);
EORA(result);
}
void RLA(uint8_t value) {
const auto result = ROL(value);
BUS().write(result);
ANDA(result);
}
void RRA(uint8_t value) {
const auto result = ROR(value);
BUS().write(result);
A() = ADC(A(), result);
}
void LAX(uint8_t value) {
adjustNZ(X() = A() = value);
}
void AAC(uint8_t value) {
ANDA(value);
setFlag(P(), CF, A() & Bit7);
}
void ASR(uint8_t value) {
A() = LSR(A() & value);
}
void ARR(uint8_t value) {
}
void ATX(uint8_t value) {
ANDA(value);
X() = A();
}
void AXS(uint8_t value) {
}
//
uint8_t DEC(uint8_t value) {
const auto result = --value;
adjustNZ(result);
return result;
}
uint8_t INC(uint8_t value) {
const auto result = ++value;
adjustNZ(result);
return result;
}
void ORA(uint8_t value) {
adjustNZ(A() |= value);
}
void ANDA(uint8_t value) {
adjustNZ(A() &= value);
}
void EORA(uint8_t value) {
adjustNZ(A() ^= value);
}
uint8_t ROR(uint8_t value);
uint8_t LSR(uint8_t value);
void BIT(uint8_t data);
uint8_t ROL(uint8_t value);
uint8_t ASL(uint8_t value);
void CMP(uint8_t first, uint8_t second);
void Branch(int8_t displacement);
void Branch(bool flag);
void PHP();
void PLP();
void JSR_abs();
void RTI();
void RTS();
void JMP_abs();
void JMP_ind();
void BRK();
// All interrupt vectors are on the 0xFF page
const uint8_t IRQvector = 0xfe;
const uint8_t RSTvector = 0xfc;
const uint8_t NMIvector = 0xfa;
uint8_t x = 0; // index register X
uint8_t y = 0; // index register Y
uint8_t a = 0; // accumulator
uint8_t s = 0; // stack pointer
uint8_t p = 0; // processor status
PinLevel m_nmiLine = Low;
PinLevel m_soLine = Low;
register16_t m_intermediate;
};
}