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/
2019-nes-emulator
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17 changed files with 480 additions and 2139 deletions
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5
CMakeLists.txt
View File

@ -10,14 +10,9 @@ add_executable(nes)
target_sources(
nes
PRIVATE
Source/Cartridge.cpp
Source/CPU/CPU.cpp
Source/CPU/AddressModes.cpp
Source/CPU/Instructions.cpp
Source/Input.cpp
Source/NES.cpp
Source/Platform.cpp
Source/PPU/PPU.cpp
Source/Main.cpp)
target_compile_options(

6
README.md
View File

@ -1,8 +1,2 @@
# NES Emulator
Unfinished NES emulator. Supports only the basic mapper, and doesn't render sprites.
[Here is a blog post about it.](https://austinmorlan.com/posts/nes_rendering_overview/)
![Demo](https://austinmorlan.com/files/nes-emulator/donkey_kong.gif)

55
Source/CPU/AddressModes.cpp
View File

@ -1,10 +1,12 @@
#include "CPU.hpp"
#include "NES.hpp"
void CPU::Implicit()
{
pc += 1;
// Do nothing
fetchedByte = acc;
}
void CPU::Immediate()
@ -12,50 +14,56 @@ void CPU::Immediate()
pc += 2;
fetchedAddress = pc - 1;
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::ZeroPage()
{
pc += 2;
fetchedAddress = nes->Read(BusSource::CPU, pc - 1);
fetchedAddress = ReadMemory(pc - 1);
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::ZeroPageX()
{
pc += 2;
uint8_t operand = nes->Read(BusSource::CPU, pc - 1);
uint8_t operand = ReadMemory(pc - 1);
fetchedAddress = (operand + x) & 0xFFu;
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::ZeroPageY()
{
pc += 2;
uint8_t operand = nes->Read(BusSource::CPU, pc - 1);
uint8_t operand = ReadMemory(pc - 1);
fetchedAddress = (operand + y) & 0xFFu;
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::Absolute()
{
pc += 3;
uint8_t addressLsb = nes->Read(BusSource::CPU, pc - 2);
uint8_t addressMsb = nes->Read(BusSource::CPU, pc - 1);
uint8_t addressLsb = ReadMemory(pc - 2);
uint8_t addressMsb = ReadMemory(pc - 1);
fetchedAddress = ComposeAddress(addressMsb, addressLsb);
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::AbsoluteX()
{
pc += 3;
uint8_t addressLsb = nes->Read(BusSource::CPU, pc - 2);
uint8_t addressMsb = nes->Read(BusSource::CPU, pc - 1);
uint8_t addressLsb = ReadMemory(pc - 2);
uint8_t addressMsb = ReadMemory(pc - 1);
uint16_t preAddress = ComposeAddress(addressMsb, addressLsb);
fetchedAddress = preAddress + x;
fetchedByte = ReadMemory(fetchedAddress);
pageBoundaryCrossed = IsPageBoundaryCrossed(preAddress, fetchedAddress);
}
@ -64,11 +72,12 @@ void CPU::AbsoluteY()
{
pc += 3;
uint8_t addressLsb = nes->Read(BusSource::CPU, pc - 2);
uint8_t addressMsb = nes->Read(BusSource::CPU, pc - 1);
uint8_t addressLsb = ReadMemory(pc - 2);
uint8_t addressMsb = ReadMemory(pc - 1);
uint16_t preAddress = ComposeAddress(addressMsb, addressLsb);
fetchedAddress = preAddress + y;
fetchedByte = ReadMemory(fetchedAddress);
pageBoundaryCrossed = IsPageBoundaryCrossed(preAddress, fetchedAddress);
}
@ -77,49 +86,52 @@ void CPU::Indirect()
{
pc += 3;
uint8_t indirectLsb = nes->Read(BusSource::CPU, pc - 2);
uint8_t indirectMsb = nes->Read(BusSource::CPU, pc - 1);
uint8_t indirectLsb = ReadMemory(pc - 2);
uint8_t indirectMsb = ReadMemory(pc - 1);
// NOTE: 6502 BUG - indirect address wraps
// $02FF + 1 = $0200
uint16_t addressIndirect = ComposeAddress(indirectMsb, indirectLsb);
uint8_t addressLsb = nes->Read(BusSource::CPU, addressIndirect);
uint8_t addressLsb = ReadMemory(addressIndirect);
// Increment LSB to read second byte - it will wrap
++indirectLsb;
addressIndirect = ComposeAddress(indirectMsb, indirectLsb);
uint8_t addressMsb = nes->Read(BusSource::CPU, addressIndirect);
uint8_t addressMsb = ReadMemory(addressIndirect);
fetchedAddress = ComposeAddress(addressMsb, addressLsb);
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::IndirectX()
{
pc += 2;
uint8_t addressIndirect = nes->Read(BusSource::CPU, pc - 1) + x;
uint8_t addressIndirect = ReadMemory(pc - 1) + x;
// Modulo to keep within zero-page
uint16_t addressLsb = nes->Read(BusSource::CPU, (addressIndirect % 0x100));
uint16_t addressMsb = nes->Read(BusSource::CPU, (addressIndirect + 1) % 0x100);
uint16_t addressLsb = ReadMemory((addressIndirect % 0x100));
uint16_t addressMsb = ReadMemory((addressIndirect + 1) % 0x100);
fetchedAddress = ComposeAddress(addressMsb, addressLsb);
fetchedByte = ReadMemory(fetchedAddress);
}
void CPU::IndirectY()
{
pc += 2;
uint8_t addressIndirect = nes->Read(BusSource::CPU, pc - 1);
uint8_t addressIndirect = ReadMemory(pc - 1);
// Modulo to keep within zero-page
uint8_t addressLsb = nes->Read(BusSource::CPU, addressIndirect % 0x100);
uint8_t addressMsb = nes->Read(BusSource::CPU, (addressIndirect + 1) % 0x100);
uint8_t addressLsb = ReadMemory(addressIndirect % 0x100);
uint8_t addressMsb = ReadMemory((addressIndirect + 1) % 0x100);
uint16_t preAddress = ComposeAddress(addressMsb, addressLsb);
fetchedAddress = preAddress + y;
fetchedByte = ReadMemory(fetchedAddress);
pageBoundaryCrossed = IsPageBoundaryCrossed(preAddress, fetchedAddress);
}
@ -128,11 +140,12 @@ void CPU::Relative()
{
pc += 2;
int8_t operand = nes->Read(BusSource::CPU, pc - 1);
int8_t operand = ReadMemory(pc - 1);
uint16_t oldPc = pc;
fetchedAddress = pc + operand;
fetchedByte = ReadMemory(fetchedAddress);
pageBoundaryCrossed = IsPageBoundaryCrossed(oldPc, fetchedAddress);
}

805
Source/CPU/CPU.cpp
View File

@ -1,333 +1,314 @@
#include <iostream>
#include <cstring>
#include "CPU.hpp"
#include "NES.hpp"
const unsigned int STACK_START_ADDRESS = 0x100u;
const unsigned int NMI_VECTOR_LSB = 0xFFFAu;
const unsigned int NMI_VECTOR_MSB = 0xFFFBu;
const unsigned int RESET_VECTOR_LSB = 0xFFFCu;
const unsigned int RESET_VECTOR_MSB = 0xFFFDu;
CPU::CPU()
{
status.SetByte(0x24);
instructions[0xA9] = Instruction{.name = "LDA", .cycles = 2, .execute = &CPU::LDA, .fetch = &CPU::Immediate};
instructions[0xA5] = Instruction{.name = "LDA", .cycles = 3, .execute = &CPU::LDA, .fetch = &CPU::ZeroPage};
instructions[0xB5] = Instruction{.name = "LDA", .cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::ZeroPageX};
instructions[0xAD] = Instruction{.name = "LDA", .cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::Absolute};
instructions[0xBD] = Instruction{.name = "LDA", .cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::AbsoluteX};
instructions[0xB9] = Instruction{.name = "LDA", .cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::AbsoluteY};
instructions[0xA1] = Instruction{.name = "LDA", .cycles = 6, .execute = &CPU::LDA, .fetch = &CPU::IndirectX};
instructions[0xB1] = Instruction{.name = "LDA", .cycles = 5, .execute = &CPU::LDA, .fetch = &CPU::IndirectY};
instructions[0xA9] = Instruction{.cycles = 2, .execute = &CPU::LDA, .fetch = &CPU::Immediate};
instructions[0xA5] = Instruction{.cycles = 3, .execute = &CPU::LDA, .fetch = &CPU::ZeroPage};
instructions[0xB5] = Instruction{.cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::ZeroPageX};
instructions[0xAD] = Instruction{.cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::Absolute};
instructions[0xBD] = Instruction{.cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::AbsoluteX};
instructions[0xB9] = Instruction{.cycles = 4, .execute = &CPU::LDA, .fetch = &CPU::AbsoluteY};
instructions[0xA1] = Instruction{.cycles = 6, .execute = &CPU::LDA, .fetch = &CPU::IndirectX};
instructions[0xB1] = Instruction{.cycles = 5, .execute = &CPU::LDA, .fetch = &CPU::IndirectY};
instructions[0xA2] = Instruction{.name = "LDX", .cycles = 2, .execute = &CPU::LDX, .fetch = &CPU::Immediate};
instructions[0xA6] = Instruction{.name = "LDX", .cycles = 3, .execute = &CPU::LDX, .fetch = &CPU::ZeroPage};
instructions[0xB6] = Instruction{.name = "LDX", .cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::ZeroPageY};
instructions[0xAE] = Instruction{.name = "LDX", .cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::Absolute};
instructions[0xBE] = Instruction{.name = "LDX", .cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::AbsoluteY};
instructions[0xA2] = Instruction{.cycles = 2, .execute = &CPU::LDX, .fetch = &CPU::Immediate};
instructions[0xA6] = Instruction{.cycles = 3, .execute = &CPU::LDX, .fetch = &CPU::ZeroPage};
instructions[0xB6] = Instruction{.cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::ZeroPageY};
instructions[0xAE] = Instruction{.cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::Absolute};
instructions[0xBE] = Instruction{.cycles = 4, .execute = &CPU::LDX, .fetch = &CPU::AbsoluteY};
instructions[0xA0] = Instruction{.name = "LDY", .cycles = 2, .execute = &CPU::LDY, .fetch = &CPU::Immediate};
instructions[0xA4] = Instruction{.name = "LDY", .cycles = 3, .execute = &CPU::LDY, .fetch = &CPU::ZeroPage};
instructions[0xB4] = Instruction{.name = "LDY", .cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::ZeroPageX};
instructions[0xAC] = Instruction{.name = "LDY", .cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::Absolute};
instructions[0xBC] = Instruction{.name = "LDY", .cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::AbsoluteX};
instructions[0xA0] = Instruction{.cycles = 2, .execute = &CPU::LDY, .fetch = &CPU::Immediate};
instructions[0xA4] = Instruction{.cycles = 3, .execute = &CPU::LDY, .fetch = &CPU::ZeroPage};
instructions[0xB4] = Instruction{.cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::ZeroPageX};
instructions[0xAC] = Instruction{.cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::Absolute};
instructions[0xBC] = Instruction{.cycles = 4, .execute = &CPU::LDY, .fetch = &CPU::AbsoluteX};
instructions[0x85] = Instruction{.name = "STA", .cycles = 3, .execute = &CPU::STA, .fetch = &CPU::ZeroPage};
instructions[0x95] = Instruction{.name = "STA", .cycles = 4, .execute = &CPU::STA, .fetch = &CPU::ZeroPageX};
instructions[0x8D] = Instruction{.name = "STA", .cycles = 4, .execute = &CPU::STA, .fetch = &CPU::Absolute};
instructions[0x9D] = Instruction{.name = "STA", .cycles = 5, .execute = &CPU::STA, .fetch = &CPU::AbsoluteX};
instructions[0x99] = Instruction{.name = "STA", .cycles = 5, .execute = &CPU::STA, .fetch = &CPU::AbsoluteY};
instructions[0x81] = Instruction{.name = "STA", .cycles = 6, .execute = &CPU::STA, .fetch = &CPU::IndirectX};
instructions[0x91] = Instruction{.name = "STA", .cycles = 6, .execute = &CPU::STA, .fetch = &CPU::IndirectY};
instructions[0x85] = Instruction{.cycles = 3, .execute = &CPU::STA, .fetch = &CPU::ZeroPage};
instructions[0x95] = Instruction{.cycles = 4, .execute = &CPU::STA, .fetch = &CPU::ZeroPageX};
instructions[0x8D] = Instruction{.cycles = 4, .execute = &CPU::STA, .fetch = &CPU::Absolute};
instructions[0x9D] = Instruction{.cycles = 5, .execute = &CPU::STA, .fetch = &CPU::AbsoluteX};
instructions[0x99] = Instruction{.cycles = 5, .execute = &CPU::STA, .fetch = &CPU::AbsoluteY};
instructions[0x81] = Instruction{.cycles = 6, .execute = &CPU::STA, .fetch = &CPU::IndirectX};
instructions[0x91] = Instruction{.cycles = 6, .execute = &CPU::STA, .fetch = &CPU::IndirectY};
instructions[0x86] = Instruction{.name = "STX", .cycles = 3, .execute = &CPU::STX, .fetch = &CPU::ZeroPage};
instructions[0x96] = Instruction{.name = "STX", .cycles = 4, .execute = &CPU::STX, .fetch = &CPU::ZeroPageY};
instructions[0x8E] = Instruction{.name = "STX", .cycles = 4, .execute = &CPU::STX, .fetch = &CPU::Absolute};
instructions[0x86] = Instruction{.cycles = 3, .execute = &CPU::STX, .fetch = &CPU::ZeroPage};
instructions[0x96] = Instruction{.cycles = 4, .execute = &CPU::STX, .fetch = &CPU::ZeroPageY};
instructions[0x8E] = Instruction{.cycles = 4, .execute = &CPU::STX, .fetch = &CPU::Absolute};
instructions[0x84] = Instruction{.name = "STY", .cycles = 3, .execute = &CPU::STY, .fetch = &CPU::ZeroPage};
instructions[0x94] = Instruction{.name = "STY", .cycles = 4, .execute = &CPU::STY, .fetch = &CPU::ZeroPageX};
instructions[0x8C] = Instruction{.name = "STY", .cycles = 4, .execute = &CPU::STY, .fetch = &CPU::Absolute};
instructions[0x84] = Instruction{.cycles = 3, .execute = &CPU::STY, .fetch = &CPU::ZeroPage};
instructions[0x94] = Instruction{.cycles = 4, .execute = &CPU::STY, .fetch = &CPU::ZeroPageX};
instructions[0x8C] = Instruction{.cycles = 4, .execute = &CPU::STY, .fetch = &CPU::Absolute};
instructions[0xAA] = Instruction{.name = "TAX", .cycles = 2, .execute = &CPU::TAX, .fetch = &CPU::Implicit};
instructions[0xA8] = Instruction{.name = "TAY", .cycles = 2, .execute = &CPU::TAY, .fetch = &CPU::Implicit};
instructions[0x8A] = Instruction{.name = "TXA", .cycles = 2, .execute = &CPU::TXA, .fetch = &CPU::Implicit};
instructions[0x98] = Instruction{.name = "TYA", .cycles = 2, .execute = &CPU::TYA, .fetch = &CPU::Implicit};
instructions[0xBA] = Instruction{.name = "TSX", .cycles = 2, .execute = &CPU::TSX, .fetch = &CPU::Implicit};
instructions[0x9A] = Instruction{.name = "TXS", .cycles = 2, .execute = &CPU::TXS, .fetch = &CPU::Implicit};
instructions[0xAA] = Instruction{.cycles = 2, .execute = &CPU::TAX, .fetch = &CPU::Implicit};
instructions[0xA8] = Instruction{.cycles = 2, .execute = &CPU::TAY, .fetch = &CPU::Implicit};
instructions[0x8A] = Instruction{.cycles = 2, .execute = &CPU::TXA, .fetch = &CPU::Implicit};
instructions[0x98] = Instruction{.cycles = 2, .execute = &CPU::TYA, .fetch = &CPU::Implicit};
instructions[0xBA] = Instruction{.cycles = 2, .execute = &CPU::TSX, .fetch = &CPU::Implicit};
instructions[0x9A] = Instruction{.cycles = 2, .execute = &CPU::TXS, .fetch = &CPU::Implicit};
instructions[0x48] = Instruction{.name = "PHA", .cycles = 3, .execute = &CPU::PHA, .fetch = &CPU::Implicit};
instructions[0x08] = Instruction{.name = "PHP", .cycles = 3, .execute = &CPU::PHP, .fetch = &CPU::Implicit};
instructions[0x68] = Instruction{.name = "PLA", .cycles = 4, .execute = &CPU::PLA, .fetch = &CPU::Implicit};
instructions[0x28] = Instruction{.name = "PLP", .cycles = 4, .execute = &CPU::PLP, .fetch = &CPU::Implicit};
instructions[0x48] = Instruction{.cycles = 3, .execute = &CPU::PHA, .fetch = &CPU::Implicit};
instructions[0x08] = Instruction{.cycles = 3, .execute = &CPU::PHP, .fetch = &CPU::Implicit};
instructions[0x68] = Instruction{.cycles = 4, .execute = &CPU::PLA, .fetch = &CPU::Implicit};
instructions[0x28] = Instruction{.cycles = 4, .execute = &CPU::PLP, .fetch = &CPU::Implicit};
instructions[0x29] = Instruction{.name = "AND", .cycles = 2, .execute = &CPU::AND, .fetch = &CPU::Immediate};
instructions[0x25] = Instruction{.name = "AND", .cycles = 3, .execute = &CPU::AND, .fetch = &CPU::ZeroPage};
instructions[0x35] = Instruction{.name = "AND", .cycles = 4, .execute = &CPU::AND, .fetch = &CPU::ZeroPageX};
instructions[0x2D] = Instruction{.name = "AND", .cycles = 4, .execute = &CPU::AND, .fetch = &CPU::Absolute};
instructions[0x3D] = Instruction{.name = "AND", .cycles = 4, .execute = &CPU::AND, .fetch = &CPU::AbsoluteX};
instructions[0x39] = Instruction{.name = "AND", .cycles = 4, .execute = &CPU::AND, .fetch = &CPU::AbsoluteY};
instructions[0x21] = Instruction{.name = "AND", .cycles = 6, .execute = &CPU::AND, .fetch = &CPU::IndirectX};
instructions[0x31] = Instruction{.name = "AND", .cycles = 5, .execute = &CPU::AND, .fetch = &CPU::IndirectY};
instructions[0x29] = Instruction{.cycles = 2, .execute = &CPU::AND, .fetch = &CPU::Immediate};
instructions[0x25] = Instruction{.cycles = 3, .execute = &CPU::AND, .fetch = &CPU::ZeroPage};
instructions[0x35] = Instruction{.cycles = 4, .execute = &CPU::AND, .fetch = &CPU::ZeroPageX};
instructions[0x2D] = Instruction{.cycles = 4, .execute = &CPU::AND, .fetch = &CPU::Absolute};
instructions[0x3D] = Instruction{.cycles = 4, .execute = &CPU::AND, .fetch = &CPU::AbsoluteX};
instructions[0x39] = Instruction{.cycles = 4, .execute = &CPU::AND, .fetch = &CPU::AbsoluteY};
instructions[0x21] = Instruction{.cycles = 6, .execute = &CPU::AND, .fetch = &CPU::IndirectX};
instructions[0x31] = Instruction{.cycles = 5, .execute = &CPU::AND, .fetch = &CPU::IndirectY};
instructions[0x49] = Instruction{.name = "EOR", .cycles = 2, .execute = &CPU::EOR, .fetch = &CPU::Immediate};
instructions[0x45] = Instruction{.name = "EOR", .cycles = 3, .execute = &CPU::EOR, .fetch = &CPU::ZeroPage};
instructions[0x55] = Instruction{.name = "EOR", .cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::ZeroPageX};
instructions[0x4D] = Instruction{.name = "EOR", .cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::Absolute};
instructions[0x5D] = Instruction{.name = "EOR", .cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::AbsoluteX};
instructions[0x59] = Instruction{.name = "EOR", .cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::AbsoluteY};
instructions[0x41] = Instruction{.name = "EOR", .cycles = 6, .execute = &CPU::EOR, .fetch = &CPU::IndirectX};
instructions[0x51] = Instruction{.name = "EOR", .cycles = 5, .execute = &CPU::EOR, .fetch = &CPU::IndirectY};
instructions[0x49] = Instruction{.cycles = 2, .execute = &CPU::EOR, .fetch = &CPU::Immediate};
instructions[0x45] = Instruction{.cycles = 3, .execute = &CPU::EOR, .fetch = &CPU::ZeroPage};
instructions[0x55] = Instruction{.cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::ZeroPageX};
instructions[0x4D] = Instruction{.cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::Absolute};
instructions[0x5D] = Instruction{.cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::AbsoluteX};
instructions[0x59] = Instruction{.cycles = 4, .execute = &CPU::EOR, .fetch = &CPU::AbsoluteY};
instructions[0x41] = Instruction{.cycles = 6, .execute = &CPU::EOR, .fetch = &CPU::IndirectX};
instructions[0x51] = Instruction{.cycles = 5, .execute = &CPU::EOR, .fetch = &CPU::IndirectY};
instructions[0x09] = Instruction{.name = "ORA", .cycles = 2, .execute = &CPU::ORA, .fetch = &CPU::Immediate};
instructions[0x05] = Instruction{.name = "ORA", .cycles = 3, .execute = &CPU::ORA, .fetch = &CPU::ZeroPage};
instructions[0x15] = Instruction{.name = "ORA", .cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::ZeroPageX};
instructions[0x0D] = Instruction{.name = "ORA", .cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::Absolute};
instructions[0x1D] = Instruction{.name = "ORA", .cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::AbsoluteX};
instructions[0x19] = Instruction{.name = "ORA", .cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::AbsoluteY};
instructions[0x01] = Instruction{.name = "ORA", .cycles = 6, .execute = &CPU::ORA, .fetch = &CPU::IndirectX};
instructions[0x11] = Instruction{.name = "ORA", .cycles = 5, .execute = &CPU::ORA, .fetch = &CPU::IndirectY};
instructions[0x09] = Instruction{.cycles = 2, .execute = &CPU::ORA, .fetch = &CPU::Immediate};
instructions[0x05] = Instruction{.cycles = 3, .execute = &CPU::ORA, .fetch = &CPU::ZeroPage};
instructions[0x15] = Instruction{.cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::ZeroPageX};
instructions[0x0D] = Instruction{.cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::Absolute};
instructions[0x1D] = Instruction{.cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::AbsoluteX};
instructions[0x19] = Instruction{.cycles = 4, .execute = &CPU::ORA, .fetch = &CPU::AbsoluteY};
instructions[0x01] = Instruction{.cycles = 6, .execute = &CPU::ORA, .fetch = &CPU::IndirectX};
instructions[0x11] = Instruction{.cycles = 5, .execute = &CPU::ORA, .fetch = &CPU::IndirectY};
instructions[0x24] = Instruction{.name = "BIT", .cycles = 3, .execute = &CPU::BIT, .fetch = &CPU::ZeroPage};
instructions[0x2C] = Instruction{.name = "BIT", .cycles = 4, .execute = &CPU::BIT, .fetch = &CPU::Absolute};
instructions[0x24] = Instruction{.cycles = 3, .execute = &CPU::BIT, .fetch = &CPU::ZeroPage};
instructions[0x2C] = Instruction{.cycles = 4, .execute = &CPU::BIT, .fetch = &CPU::Absolute};
instructions[0x69] = Instruction{.name = "ADC", .cycles = 2, .execute = &CPU::ADC, .fetch = &CPU::Immediate};
instructions[0x65] = Instruction{.name = "ADC", .cycles = 3, .execute = &CPU::ADC, .fetch = &CPU::ZeroPage};
instructions[0x75] = Instruction{.name = "ADC", .cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::ZeroPageX};
instructions[0x6D] = Instruction{.name = "ADC", .cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::Absolute};
instructions[0x7D] = Instruction{.name = "ADC", .cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::AbsoluteX};
instructions[0x79] = Instruction{.name = "ADC", .cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::AbsoluteY};
instructions[0x61] = Instruction{.name = "ADC", .cycles = 6, .execute = &CPU::ADC, .fetch = &CPU::IndirectX};
instructions[0x71] = Instruction{.name = "ADC", .cycles = 5, .execute = &CPU::ADC, .fetch = &CPU::IndirectY};
instructions[0x69] = Instruction{.cycles = 2, .execute = &CPU::ADC, .fetch = &CPU::Immediate};
instructions[0x65] = Instruction{.cycles = 3, .execute = &CPU::ADC, .fetch = &CPU::ZeroPage};
instructions[0x75] = Instruction{.cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::ZeroPageX};
instructions[0x6D] = Instruction{.cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::Absolute};
instructions[0x7D] = Instruction{.cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::AbsoluteX};
instructions[0x79] = Instruction{.cycles = 4, .execute = &CPU::ADC, .fetch = &CPU::AbsoluteY};
instructions[0x61] = Instruction{.cycles = 6, .execute = &CPU::ADC, .fetch = &CPU::IndirectX};
instructions[0x71] = Instruction{.cycles = 5, .execute = &CPU::ADC, .fetch = &CPU::IndirectY};
instructions[0xE9] = Instruction{.name = "SBC", .cycles = 2, .execute = &CPU::SBC, .fetch = &CPU::Immediate};
instructions[0xE5] = Instruction{.name = "SBC", .cycles = 3, .execute = &CPU::SBC, .fetch = &CPU::ZeroPage};
instructions[0xF5] = Instruction{.name = "SBC", .cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::ZeroPageX};
instructions[0xED] = Instruction{.name = "SBC", .cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::Absolute};
instructions[0xFD] = Instruction{.name = "SBC", .cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::AbsoluteX};
instructions[0xF9] = Instruction{.name = "SBC", .cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::AbsoluteY};
instructions[0xE1] = Instruction{.name = "SBC", .cycles = 6, .execute = &CPU::SBC, .fetch = &CPU::IndirectX};
instructions[0xF1] = Instruction{.name = "SBC", .cycles = 5, .execute = &CPU::SBC, .fetch = &CPU::IndirectY};
instructions[0xE9] = Instruction{.cycles = 2, .execute = &CPU::SBC, .fetch = &CPU::Immediate};
instructions[0xE5] = Instruction{.cycles = 3, .execute = &CPU::SBC, .fetch = &CPU::ZeroPage};
instructions[0xF5] = Instruction{.cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::ZeroPageX};
instructions[0xED] = Instruction{.cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::Absolute};
instructions[0xFD] = Instruction{.cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::AbsoluteX};
instructions[0xF9] = Instruction{.cycles = 4, .execute = &CPU::SBC, .fetch = &CPU::AbsoluteY};
instructions[0xE1] = Instruction{.cycles = 6, .execute = &CPU::SBC, .fetch = &CPU::IndirectX};
instructions[0xF1] = Instruction{.cycles = 5, .execute = &CPU::SBC, .fetch = &CPU::IndirectY};
instructions[0xC9] = Instruction{.name = "CMP", .cycles = 2, .execute = &CPU::CMP, .fetch = &CPU::Immediate};
instructions[0xC5] = Instruction{.name = "CMP", .cycles = 3, .execute = &CPU::CMP, .fetch = &CPU::ZeroPage};
instructions[0xD5] = Instruction{.name = "CMP", .cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::ZeroPageX};
instructions[0xCD] = Instruction{.name = "CMP", .cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::Absolute};
instructions[0xDD] = Instruction{.name = "CMP", .cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::AbsoluteX};
instructions[0xD9] = Instruction{.name = "CMP", .cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::AbsoluteY};
instructions[0xC1] = Instruction{.name = "CMP", .cycles = 6, .execute = &CPU::CMP, .fetch = &CPU::IndirectX};
instructions[0xD1] = Instruction{.name = "CMP", .cycles = 5, .execute = &CPU::CMP, .fetch = &CPU::IndirectY};
instructions[0xC9] = Instruction{.cycles = 2, .execute = &CPU::CMP, .fetch = &CPU::Immediate};
instructions[0xC5] = Instruction{.cycles = 3, .execute = &CPU::CMP, .fetch = &CPU::ZeroPage};
instructions[0xD5] = Instruction{.cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::ZeroPageX};
instructions[0xCD] = Instruction{.cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::Absolute};
instructions[0xDD] = Instruction{.cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::AbsoluteX};
instructions[0xD9] = Instruction{.cycles = 4, .execute = &CPU::CMP, .fetch = &CPU::AbsoluteY};
instructions[0xC1] = Instruction{.cycles = 6, .execute = &CPU::CMP, .fetch = &CPU::IndirectX};
instructions[0xD1] = Instruction{.cycles = 5, .execute = &CPU::CMP, .fetch = &CPU::IndirectY};
instructions[0xE0] = Instruction{.name = "CPX", .cycles = 2, .execute = &CPU::CPX, .fetch = &CPU::Immediate};
instructions[0xE4] = Instruction{.name = "CPX", .cycles = 3, .execute = &CPU::CPX, .fetch = &CPU::ZeroPage};
instructions[0xEC] = Instruction{.name = "CPX", .cycles = 4, .execute = &CPU::CPX, .fetch = &CPU::Absolute};
instructions[0xE0] = Instruction{.cycles = 2, .execute = &CPU::CPX, .fetch = &CPU::Immediate};
instructions[0xE4] = Instruction{.cycles = 3, .execute = &CPU::CPX, .fetch = &CPU::ZeroPage};
instructions[0xEC] = Instruction{.cycles = 4, .execute = &CPU::CPX, .fetch = &CPU::Absolute};
instructions[0xC0] = Instruction{.name = "CPY", .cycles = 2, .execute = &CPU::CPY, .fetch = &CPU::Immediate};
instructions[0xC4] = Instruction{.name = "CPY", .cycles = 3, .execute = &CPU::CPY, .fetch = &CPU::ZeroPage};
instructions[0xCC] = Instruction{.name = "CPY", .cycles = 4, .execute = &CPU::CPY, .fetch = &CPU::Absolute};
instructions[0xC0] = Instruction{.cycles = 2, .execute = &CPU::CPY, .fetch = &CPU::Immediate};
instructions[0xC4] = Instruction{.cycles = 3, .execute = &CPU::CPY, .fetch = &CPU::ZeroPage};
instructions[0xCC] = Instruction{.cycles = 4, .execute = &CPU::CPY, .fetch = &CPU::Absolute};
instructions[0xE6] = Instruction{.name = "INC", .cycles = 5, .execute = &CPU::INC, .fetch = &CPU::ZeroPage};
instructions[0xF6] = Instruction{.name = "INC", .cycles = 6, .execute = &CPU::INC, .fetch = &CPU::ZeroPageX};
instructions[0xEE] = Instruction{.name = "INC", .cycles = 6, .execute = &CPU::INC, .fetch = &CPU::Absolute};
instructions[0xFE] = Instruction{.name = "INC", .cycles = 7, .execute = &CPU::INC, .fetch = &CPU::AbsoluteX};
instructions[0xE6] = Instruction{.cycles = 5, .execute = &CPU::INC, .fetch = &CPU::ZeroPage};
instructions[0xF6] = Instruction{.cycles = 6, .execute = &CPU::INC, .fetch = &CPU::ZeroPageX};
instructions[0xEE] = Instruction{.cycles = 6, .execute = &CPU::INC, .fetch = &CPU::Absolute};
instructions[0xFE] = Instruction{.cycles = 7, .execute = &CPU::INC, .fetch = &CPU::AbsoluteX};
instructions[0xE8] = Instruction{.name = "INX", .cycles = 2, .execute = &CPU::INX, .fetch = &CPU::Implicit};
instructions[0xE8] = Instruction{.cycles = 2, .execute = &CPU::INX, .fetch = &CPU::Implicit};
instructions[0xC8] = Instruction{.name = "INY", .cycles = 2, .execute = &CPU::INY, .fetch = &CPU::Implicit};
instructions[0xC8] = Instruction{.cycles = 2, .execute = &CPU::INY, .fetch = &CPU::Implicit};
instructions[0xC6] = Instruction{.name = "DEC", .cycles = 5, .execute = &CPU::DEC, .fetch = &CPU::ZeroPage};
instructions[0xD6] = Instruction{.name = "DEC", .cycles = 6, .execute = &CPU::DEC, .fetch = &CPU::ZeroPageX};
instructions[0xCE] = Instruction{.name = "DEC", .cycles = 6, .execute = &CPU::DEC, .fetch = &CPU::Absolute};
instructions[0xDE] = Instruction{.name = "DEC", .cycles = 7, .execute = &CPU::DEC, .fetch = &CPU::AbsoluteX};
instructions[0xC6] = Instruction{.cycles = 5, .execute = &CPU::DEC, .fetch = &CPU::ZeroPage};
instructions[0xD6] = Instruction{.cycles = 6, .execute = &CPU::DEC, .fetch = &CPU::ZeroPageX};
instructions[0xCE] = Instruction{.cycles = 6, .execute = &CPU::DEC, .fetch = &CPU::Absolute};
instructions[0xDE] = Instruction{.cycles = 7, .execute = &CPU::DEC, .fetch = &CPU::AbsoluteX};
instructions[0xCA] = Instruction{.name = "DEX", .cycles = 2, .execute = &CPU::DEX, .fetch = &CPU::Implicit};
instructions[0xCA] = Instruction{.cycles = 2, .execute = &CPU::DEX, .fetch = &CPU::Implicit};
instructions[0x88] = Instruction{.name = "DEY", .cycles = 2, .execute = &CPU::DEY, .fetch = &CPU::Implicit};
instructions[0x88] = Instruction{.cycles = 2, .execute = &CPU::DEY, .fetch = &CPU::Implicit};
instructions[0x0A] = Instruction{.name = "ASL", .cycles = 2, .execute = &CPU::ASL, .fetch = &CPU::Implicit};
instructions[0x06] = Instruction{.name = "ASL", .cycles = 5, .execute = &CPU::ASL, .fetch = &CPU::ZeroPage};
instructions[0x16] = Instruction{.name = "ASL", .cycles = 6, .execute = &CPU::ASL, .fetch = &CPU::ZeroPageX};
instructions[0x0E] = Instruction{.name = "ASL", .cycles = 6, .execute = &CPU::ASL, .fetch = &CPU::Absolute};
instructions[0x1E] = Instruction{.name = "ASL", .cycles = 7, .execute = &CPU::ASL, .fetch = &CPU::AbsoluteX};
instructions[0x0A] = Instruction{.cycles = 2, .execute = &CPU::ASL, .fetch = &CPU::Implicit};
instructions[0x06] = Instruction{.cycles = 5, .execute = &CPU::ASL, .fetch = &CPU::ZeroPage};
instructions[0x16] = Instruction{.cycles = 6, .execute = &CPU::ASL, .fetch = &CPU::ZeroPageX};
instructions[0x0E] = Instruction{.cycles = 6, .execute = &CPU::ASL, .fetch = &CPU::Absolute};
instructions[0x1E] = Instruction{.cycles = 7, .execute = &CPU::ASL, .fetch = &CPU::AbsoluteX};
instructions[0x4A] = Instruction{.name = "LSR", .cycles = 2, .execute = &CPU::LSR, .fetch = &CPU::Implicit};
instructions[0x46] = Instruction{.name = "LSR", .cycles = 5, .execute = &CPU::LSR, .fetch = &CPU::ZeroPage};
instructions[0x56] = Instruction{.name = "LSR", .cycles = 6, .execute = &CPU::LSR, .fetch = &CPU::ZeroPageX};
instructions[0x4E] = Instruction{.name = "LSR", .cycles = 6, .execute = &CPU::LSR, .fetch = &CPU::Absolute};
instructions[0x5E] = Instruction{.name = "LSR", .cycles = 7, .execute = &CPU::LSR, .fetch = &CPU::AbsoluteX};
instructions[0x4A] = Instruction{.cycles = 2, .execute = &CPU::LSR, .fetch = &CPU::Implicit};
instructions[0x46] = Instruction{.cycles = 5, .execute = &CPU::LSR, .fetch = &CPU::ZeroPage};
instructions[0x56] = Instruction{.cycles = 6, .execute = &CPU::LSR, .fetch = &CPU::ZeroPageX};
instructions[0x4E] = Instruction{.cycles = 6, .execute = &CPU::LSR, .fetch = &CPU::Absolute};
instructions[0x5E] = Instruction{.cycles = 7, .execute = &CPU::LSR, .fetch = &CPU::AbsoluteX};
instructions[0x2A] = Instruction{.name = "ROL", .cycles = 2, .execute = &CPU::ROL, .fetch = &CPU::Implicit};
instructions[0x26] = Instruction{.name = "ROL", .cycles = 5, .execute = &CPU::ROL, .fetch = &CPU::ZeroPage};
instructions[0x36] = Instruction{.name = "ROL", .cycles = 6, .execute = &CPU::ROL, .fetch = &CPU::ZeroPageX};
instructions[0x2E] = Instruction{.name = "ROL", .cycles = 6, .execute = &CPU::ROL, .fetch = &CPU::Absolute};
instructions[0x3E] = Instruction{.name = "ROL", .cycles = 7, .execute = &CPU::ROL, .fetch = &CPU::AbsoluteX};
instructions[0x2A] = Instruction{.cycles = 2, .execute = &CPU::ROL, .fetch = &CPU::Implicit};
instructions[0x26] = Instruction{.cycles = 5, .execute = &CPU::ROL, .fetch = &CPU::ZeroPage};
instructions[0x36] = Instruction{.cycles = 6, .execute = &CPU::ROL, .fetch = &CPU::ZeroPageX};
instructions[0x2E] = Instruction{.cycles = 6, .execute = &CPU::ROL, .fetch = &CPU::Absolute};
instructions[0x3E] = Instruction{.cycles = 7, .execute = &CPU::ROL, .fetch = &CPU::AbsoluteX};
instructions[0x6A] = Instruction{.name = "ROR", .cycles = 2, .execute = &CPU::ROR, .fetch = &CPU::Implicit};
instructions[0x66] = Instruction{.name = "ROR", .cycles = 5, .execute = &CPU::ROR, .fetch = &CPU::ZeroPage};
instructions[0x76] = Instruction{.name = "ROR", .cycles = 6, .execute = &CPU::ROR, .fetch = &CPU::ZeroPageX};
instructions[0x6E] = Instruction{.name = "ROR", .cycles = 6, .execute = &CPU::ROR, .fetch = &CPU::Absolute};
instructions[0x7E] = Instruction{.name = "ROR", .cycles = 7, .execute = &CPU::ROR, .fetch = &CPU::AbsoluteX};
instructions[0x6A] = Instruction{.cycles = 2, .execute = &CPU::ROR, .fetch = &CPU::Implicit};
instructions[0x66] = Instruction{.cycles = 5, .execute = &CPU::ROR, .fetch = &CPU::ZeroPage};
instructions[0x76] = Instruction{.cycles = 6, .execute = &CPU::ROR, .fetch = &CPU::ZeroPageX};
instructions[0x6E] = Instruction{.cycles = 6, .execute = &CPU::ROR, .fetch = &CPU::Absolute};
instructions[0x7E] = Instruction{.cycles = 7, .execute = &CPU::ROR, .fetch = &CPU::AbsoluteX};
instructions[0x4C] = Instruction{.name = "JMP", .cycles = 3, .execute = &CPU::JMP, .fetch = &CPU::Absolute};
instructions[0x6C] = Instruction{.name = "JMP", .cycles = 5, .execute = &CPU::JMP, .fetch = &CPU::Indirect};
instructions[0x4C] = Instruction{.cycles = 3, .execute = &CPU::JMP, .fetch = &CPU::Absolute};
instructions[0x6C] = Instruction{.cycles = 5, .execute = &CPU::JMP, .fetch = &CPU::Indirect};
instructions[0x20] = Instruction{.name = "JSR", .cycles = 6, .execute = &CPU::JSR, .fetch = &CPU::Absolute};
instructions[0x20] = Instruction{.cycles = 6, .execute = &CPU::JSR, .fetch = &CPU::Absolute};
instructions[0x60] = Instruction{.name = "RTS", .cycles = 6, .execute = &CPU::RTS, .fetch = &CPU::Implicit};
instructions[0x60] = Instruction{.cycles = 6, .execute = &CPU::RTS, .fetch = &CPU::Implicit};
instructions[0x90] = Instruction{.name = "BCC", .cycles = 2, .execute = &CPU::BCC, .fetch = &CPU::Relative};
instructions[0xB0] = Instruction{.name = "BCS", .cycles = 2, .execute = &CPU::BCS, .fetch = &CPU::Relative};
instructions[0xF0] = Instruction{.name = "BEQ", .cycles = 2, .execute = &CPU::BEQ, .fetch = &CPU::Relative};
instructions[0x30] = Instruction{.name = "BMI", .cycles = 2, .execute = &CPU::BMI, .fetch = &CPU::Relative};
instructions[0xD0] = Instruction{.name = "BNE", .cycles = 2, .execute = &CPU::BNE, .fetch = &CPU::Relative};
instructions[0x10] = Instruction{.name = "BPL", .cycles = 2, .execute = &CPU::BPL, .fetch = &CPU::Relative};
instructions[0x50] = Instruction{.name = "BVC", .cycles = 2, .execute = &CPU::BVC, .fetch = &CPU::Relative};
instructions[0x70] = Instruction{.name = "BVS", .cycles = 2, .execute = &CPU::BVS, .fetch = &CPU::Relative};
instructions[0x90] = Instruction{.cycles = 2, .execute = &CPU::BCC, .fetch = &CPU::Relative};
instructions[0xB0] = Instruction{.cycles = 2, .execute = &CPU::BCS, .fetch = &CPU::Relative};
instructions[0xF0] = Instruction{.cycles = 2, .execute = &CPU::BEQ, .fetch = &CPU::Relative};
instructions[0x30] = Instruction{.cycles = 2, .execute = &CPU::BMI, .fetch = &CPU::Relative};
instructions[0xD0] = Instruction{.cycles = 2, .execute = &CPU::BNE, .fetch = &CPU::Relative};
instructions[0x10] = Instruction{.cycles = 2, .execute = &CPU::BPL, .fetch = &CPU::Relative};
instructions[0x50] = Instruction{.cycles = 2, .execute = &CPU::BVC, .fetch = &CPU::Relative};
instructions[0x70] = Instruction{.cycles = 2, .execute = &CPU::BVS, .fetch = &CPU::Relative};
instructions[0x18] = Instruction{.name = "CLC", .cycles = 2, .execute = &CPU::CLC, .fetch = &CPU::Implicit};
instructions[0xD8] = Instruction{.name = "CLD", .cycles = 2, .execute = &CPU::CLD, .fetch = &CPU::Implicit};
instructions[0x58] = Instruction{.name = "CLI", .cycles = 2, .execute = &CPU::CLI, .fetch = &CPU::Implicit};
instructions[0xB8] = Instruction{.name = "CLV", .cycles = 2, .execute = &CPU::CLV, .fetch = &CPU::Implicit};
instructions[0x38] = Instruction{.name = "SEC", .cycles = 2, .execute = &CPU::SEC, .fetch = &CPU::Implicit};
instructions[0xF8] = Instruction{.name = "SED", .cycles = 2, .execute = &CPU::SED, .fetch = &CPU::Implicit};
instructions[0x78] = Instruction{.name = "SEI", .cycles = 2, .execute = &CPU::SEI, .fetch = &CPU::Implicit};
instructions[0x18] = Instruction{.cycles = 2, .execute = &CPU::CLC, .fetch = &CPU::Implicit};
instructions[0xD8] = Instruction{.cycles = 2, .execute = &CPU::CLD, .fetch = &CPU::Implicit};
instructions[0x58] = Instruction{.cycles = 2, .execute = &CPU::CLI, .fetch = &CPU::Implicit};
instructions[0xB8] = Instruction{.cycles = 2, .execute = &CPU::CLV, .fetch = &CPU::Implicit};
instructions[0x38] = Instruction{.cycles = 2, .execute = &CPU::SEC, .fetch = &CPU::Implicit};
instructions[0xF8] = Instruction{.cycles = 2, .execute = &CPU::SED, .fetch = &CPU::Implicit};
instructions[0x78] = Instruction{.cycles = 2, .execute = &CPU::SEI, .fetch = &CPU::Implicit};
instructions[0x00] = Instruction{.name = "BRK", .cycles = 7, .execute = &CPU::BRK, .fetch = &CPU::Immediate};
instructions[0xEA] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x40] = Instruction{.name = "RTI", .cycles = 6, .execute = &CPU::RTI, .fetch = &CPU::Implicit};
instructions[0x00] = Instruction{.cycles = 7, .execute = &CPU::BRK, .fetch = &CPU::Implicit};
instructions[0xEA] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x40] = Instruction{.cycles = 6, .execute = &CPU::RTI, .fetch = &CPU::Implicit};
instructions[0x1A] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x3A] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x5A] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x7A] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xDA] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xFA] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x80] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x82] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x89] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0xC2] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0xE2] = Instruction{.name = "NOP", .cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x04] = Instruction{.name = "NOP", .cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x44] = Instruction{.name = "NOP", .cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x64] = Instruction{.name = "NOP", .cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x14] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x34] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x54] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x74] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0xD4] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0xF4] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x0C] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::Absolute};
instructions[0x1C] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x3C] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x5C] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x7C] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0xDC] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0xFC] = Instruction{.name = "NOP", .cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x1A] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x3A] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x5A] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x7A] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xDA] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xFA] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x80] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x82] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x89] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0xC2] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0xE2] = Instruction{.cycles = 2, .execute = &CPU::NOP, .fetch = &CPU::Immediate};
instructions[0x04] = Instruction{.cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x44] = Instruction{.cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x64] = Instruction{.cycles = 3, .execute = &CPU::NOP, .fetch = &CPU::ZeroPage};
instructions[0x14] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x34] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x54] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x74] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0xD4] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0xF4] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::ZeroPageX};
instructions[0x0C] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::Absolute};
instructions[0x1C] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x3C] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x5C] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x7C] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0xDC] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0xFC] = Instruction{.cycles = 4, .execute = &CPU::NOP, .fetch = &CPU::AbsoluteX};
instructions[0x07] = Instruction{.name = "SLO", .cycles = 5, .execute = &CPU::SLO, .fetch = &CPU::ZeroPage};
instructions[0x17] = Instruction{.name = "SLO", .cycles = 6, .execute = &CPU::SLO, .fetch = &CPU::ZeroPageX};
instructions[0x0F] = Instruction{.name = "SLO", .cycles = 6, .execute = &CPU::SLO, .fetch = &CPU::Absolute};
instructions[0x1F] = Instruction{.name = "SLO", .cycles = 7, .execute = &CPU::SLO, .fetch = &CPU::AbsoluteX};
instructions[0x1B] = Instruction{.name = "SLO", .cycles = 7, .execute = &CPU::SLO, .fetch = &CPU::AbsoluteY};
instructions[0x03] = Instruction{.name = "SLO", .cycles = 8, .execute = &CPU::SLO, .fetch = &CPU::IndirectX};
instructions[0x13] = Instruction{.name = "SLO", .cycles = 8, .execute = &CPU::SLO, .fetch = &CPU::IndirectY};
instructions[0x07] = Instruction{.cycles = 5, .execute = &CPU::SLO, .fetch = &CPU::ZeroPage};
instructions[0x17] = Instruction{.cycles = 6, .execute = &CPU::SLO, .fetch = &CPU::ZeroPageX};
instructions[0x0F] = Instruction{.cycles = 6, .execute = &CPU::SLO, .fetch = &CPU::Absolute};
instructions[0x1F] = Instruction{.cycles = 7, .execute = &CPU::SLO, .fetch = &CPU::AbsoluteX};
instructions[0x1B] = Instruction{.cycles = 7, .execute = &CPU::SLO, .fetch = &CPU::AbsoluteY};
instructions[0x03] = Instruction{.cycles = 8, .execute = &CPU::SLO, .fetch = &CPU::IndirectX};
instructions[0x13] = Instruction{.cycles = 8, .execute = &CPU::SLO, .fetch = &CPU::IndirectY};
instructions[0x27] = Instruction{.name = "RLA", .cycles = 5, .execute = &CPU::RLA, .fetch = &CPU::ZeroPage};
instructions[0x37] = Instruction{.name = "RLA", .cycles = 6, .execute = &CPU::RLA, .fetch = &CPU::ZeroPageX};
instructions[0x2F] = Instruction{.name = "RLA", .cycles = 6, .execute = &CPU::RLA, .fetch = &CPU::Absolute};
instructions[0x3F] = Instruction{.name = "RLA", .cycles = 7, .execute = &CPU::RLA, .fetch = &CPU::AbsoluteX};
instructions[0x3B] = Instruction{.name = "RLA", .cycles = 7, .execute = &CPU::RLA, .fetch = &CPU::AbsoluteY};
instructions[0x23] = Instruction{.name = "RLA", .cycles = 8, .execute = &CPU::RLA, .fetch = &CPU::IndirectX};
instructions[0x33] = Instruction{.name = "RLA", .cycles = 8, .execute = &CPU::RLA, .fetch = &CPU::IndirectY};
instructions[0x27] = Instruction{.cycles = 5, .execute = &CPU::RLA, .fetch = &CPU::ZeroPage};
instructions[0x37] = Instruction{.cycles = 6, .execute = &CPU::RLA, .fetch = &CPU::ZeroPageX};
instructions[0x2F] = Instruction{.cycles = 6, .execute = &CPU::RLA, .fetch = &CPU::Absolute};
instructions[0x3F] = Instruction{.cycles = 7, .execute = &CPU::RLA, .fetch = &CPU::AbsoluteX};
instructions[0x3B] = Instruction{.cycles = 7, .execute = &CPU::RLA, .fetch = &CPU::AbsoluteY};
instructions[0x23] = Instruction{.cycles = 8, .execute = &CPU::RLA, .fetch = &CPU::IndirectX};
instructions[0x33] = Instruction{.cycles = 8, .execute = &CPU::RLA, .fetch = &CPU::IndirectY};
instructions[0x47] = Instruction{.name = "SRE", .cycles = 5, .execute = &CPU::SRE, .fetch = &CPU::ZeroPage};
instructions[0x57] = Instruction{.name = "SRE", .cycles = 6, .execute = &CPU::SRE, .fetch = &CPU::ZeroPageX};
instructions[0x4F] = Instruction{.name = "SRE", .cycles = 6, .execute = &CPU::SRE, .fetch = &CPU::Absolute};
instructions[0x5F] = Instruction{.name = "SRE", .cycles = 7, .execute = &CPU::SRE, .fetch = &CPU::AbsoluteX};
instructions[0x5B] = Instruction{.name = "SRE", .cycles = 7, .execute = &CPU::SRE, .fetch = &CPU::AbsoluteY};
instructions[0x43] = Instruction{.name = "SRE", .cycles = 8, .execute = &CPU::SRE, .fetch = &CPU::IndirectX};
instructions[0x53] = Instruction{.name = "SRE", .cycles = 8, .execute = &CPU::SRE, .fetch = &CPU::IndirectY};
instructions[0x47] = Instruction{.cycles = 5, .execute = &CPU::SRE, .fetch = &CPU::ZeroPage};
instructions[0x57] = Instruction{.cycles = 6, .execute = &CPU::SRE, .fetch = &CPU::ZeroPageX};
instructions[0x4F] = Instruction{.cycles = 6, .execute = &CPU::SRE, .fetch = &CPU::Absolute};
instructions[0x5F] = Instruction{.cycles = 7, .execute = &CPU::SRE, .fetch = &CPU::AbsoluteX};
instructions[0x5B] = Instruction{.cycles = 7, .execute = &CPU::SRE, .fetch = &CPU::AbsoluteY};
instructions[0x43] = Instruction{.cycles = 8, .execute = &CPU::SRE, .fetch = &CPU::IndirectX};
instructions[0x53] = Instruction{.cycles = 8, .execute = &CPU::SRE, .fetch = &CPU::IndirectY};
instructions[0x67] = Instruction{.name = "RRA", .cycles = 5, .execute = &CPU::RRA, .fetch = &CPU::ZeroPage};
instructions[0x77] = Instruction{.name = "RRA", .cycles = 6, .execute = &CPU::RRA, .fetch = &CPU::ZeroPageX};
instructions[0x6F] = Instruction{.name = "RRA", .cycles = 6, .execute = &CPU::RRA, .fetch = &CPU::Absolute};
instructions[0x7F] = Instruction{.name = "RRA", .cycles = 7, .execute = &CPU::RRA, .fetch = &CPU::AbsoluteX};
instructions[0x7B] = Instruction{.name = "RRA", .cycles = 7, .execute = &CPU::RRA, .fetch = &CPU::AbsoluteY};
instructions[0x63] = Instruction{.name = "RRA", .cycles = 8, .execute = &CPU::RRA, .fetch = &CPU::IndirectX};
instructions[0x73] = Instruction{.name = "RRA", .cycles = 8, .execute = &CPU::RRA, .fetch = &CPU::IndirectY};
instructions[0x67] = Instruction{.cycles = 5, .execute = &CPU::RRA, .fetch = &CPU::ZeroPage};
instructions[0x77] = Instruction{.cycles = 6, .execute = &CPU::RRA, .fetch = &CPU::ZeroPageX};
instructions[0x6F] = Instruction{.cycles = 6, .execute = &CPU::RRA, .fetch = &CPU::Absolute};
instructions[0x7F] = Instruction{.cycles = 7, .execute = &CPU::RRA, .fetch = &CPU::AbsoluteX};
instructions[0x7B] = Instruction{.cycles = 7, .execute = &CPU::RRA, .fetch = &CPU::AbsoluteY};
instructions[0x63] = Instruction{.cycles = 8, .execute = &CPU::RRA, .fetch = &CPU::IndirectX};
instructions[0x73] = Instruction{.cycles = 8, .execute = &CPU::RRA, .fetch = &CPU::IndirectY};
instructions[0x87] = Instruction{.name = "SAX", .cycles = 3, .execute = &CPU::SAX, .fetch = &CPU::ZeroPage};
instructions[0x97] = Instruction{.name = "SAX", .cycles = 4, .execute = &CPU::SAX, .fetch = &CPU::ZeroPageY};
instructions[0x8F] = Instruction{.name = "SAX", .cycles = 4, .execute = &CPU::SAX, .fetch = &CPU::Absolute};
instructions[0x83] = Instruction{.name = "SAX", .cycles = 6, .execute = &CPU::SAX, .fetch = &CPU::IndirectX};
instructions[0x87] = Instruction{.cycles = 3, .execute = &CPU::SAX, .fetch = &CPU::ZeroPage};
instructions[0x97] = Instruction{.cycles = 4, .execute = &CPU::SAX, .fetch = &CPU::ZeroPageY};
instructions[0x8F] = Instruction{.cycles = 4, .execute = &CPU::SAX, .fetch = &CPU::Absolute};
instructions[0x83] = Instruction{.cycles = 6, .execute = &CPU::SAX, .fetch = &CPU::IndirectX};
instructions[0xEB] = Instruction{.name = "SBC", .cycles = 2, .execute = &CPU::SBC, .fetch = &CPU::Immediate};
instructions[0xEB] = Instruction{.cycles = 2, .execute = &CPU::SBC, .fetch = &CPU::Immediate};
instructions[0xAB] = Instruction{.name = "LAX", .cycles = 2, .execute = &CPU::LAX, .fetch = &CPU::Immediate};
instructions[0xA7] = Instruction{.name = "LAX", .cycles = 3, .execute = &CPU::LAX, .fetch = &CPU::ZeroPage};
instructions[0xB7] = Instruction{.name = "LAX", .cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::ZeroPageY};
instructions[0xAF] = Instruction{.name = "LAX", .cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::Absolute};
instructions[0xBF] = Instruction{.name = "LAX", .cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::AbsoluteY};
instructions[0xA3] = Instruction{.name = "LAX", .cycles = 6, .execute = &CPU::LAX, .fetch = &CPU::IndirectX};
instructions[0xB3] = Instruction{.name = "LAX", .cycles = 5, .execute = &CPU::LAX, .fetch = &CPU::IndirectY};
instructions[0xAB] = Instruction{.cycles = 2, .execute = &CPU::LAX, .fetch = &CPU::Immediate};
instructions[0xA7] = Instruction{.cycles = 3, .execute = &CPU::LAX, .fetch = &CPU::ZeroPage};
instructions[0xB7] = Instruction{.cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::ZeroPageY};
instructions[0xAF] = Instruction{.cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::Absolute};
instructions[0xBF] = Instruction{.cycles = 4, .execute = &CPU::LAX, .fetch = &CPU::AbsoluteY};
instructions[0xA3] = Instruction{.cycles = 6, .execute = &CPU::LAX, .fetch = &CPU::IndirectX};
instructions[0xB3] = Instruction{.cycles = 5, .execute = &CPU::LAX, .fetch = &CPU::IndirectY};
instructions[0xC7] = Instruction{.name = "DCP", .cycles = 5, .execute = &CPU::DCP, .fetch = &CPU::ZeroPage};
instructions[0xD7] = Instruction{.name = "DCP", .cycles = 6, .execute = &CPU::DCP, .fetch = &CPU::ZeroPageX};
instructions[0xCF] = Instruction{.name = "DCP", .cycles = 6, .execute = &CPU::DCP, .fetch = &CPU::Absolute};
instructions[0xDF] = Instruction{.name = "DCP", .cycles = 7, .execute = &CPU::DCP, .fetch = &CPU::AbsoluteX};
instructions[0xDB] = Instruction{.name = "DCP", .cycles = 7, .execute = &CPU::DCP, .fetch = &CPU::AbsoluteY};
instructions[0xC3] = Instruction{.name = "DCP", .cycles = 8, .execute = &CPU::DCP, .fetch = &CPU::IndirectX};
instructions[0xD3] = Instruction{.name = "DCP", .cycles = 8, .execute = &CPU::DCP, .fetch = &CPU::IndirectY};
instructions[0xC7] = Instruction{.cycles = 5, .execute = &CPU::DCP, .fetch = &CPU::ZeroPage};
instructions[0xD7] = Instruction{.cycles = 6, .execute = &CPU::DCP, .fetch = &CPU::ZeroPageX};
instructions[0xCF] = Instruction{.cycles = 6, .execute = &CPU::DCP, .fetch = &CPU::Absolute};
instructions[0xDF] = Instruction{.cycles = 7, .execute = &CPU::DCP, .fetch = &CPU::AbsoluteX};
instructions[0xDB] = Instruction{.cycles = 7, .execute = &CPU::DCP, .fetch = &CPU::AbsoluteY};
instructions[0xC3] = Instruction{.cycles = 8, .execute = &CPU::DCP, .fetch = &CPU::IndirectX};
instructions[0xD3] = Instruction{.cycles = 8, .execute = &CPU::DCP, .fetch = &CPU::IndirectY};
instructions[0xE7] = Instruction{.name = "ISC", .cycles = 5, .execute = &CPU::ISC, .fetch = &CPU::ZeroPage};
instructions[0xF7] = Instruction{.name = "ISC", .cycles = 6, .execute = &CPU::ISC, .fetch = &CPU::ZeroPageX};
instructions[0xEF] = Instruction{.name = "ISC", .cycles = 6, .execute = &CPU::ISC, .fetch = &CPU::Absolute};
instructions[0xFF] = Instruction{.name = "ISC", .cycles = 7, .execute = &CPU::ISC, .fetch = &CPU::AbsoluteX};
instructions[0xFB] = Instruction{.name = "ISC", .cycles = 7, .execute = &CPU::ISC, .fetch = &CPU::AbsoluteY};
instructions[0xE3] = Instruction{.name = "ISC", .cycles = 8, .execute = &CPU::ISC, .fetch = &CPU::IndirectX};
instructions[0xF3] = Instruction{.name = "ISC", .cycles = 8, .execute = &CPU::ISC, .fetch = &CPU::IndirectY};
instructions[0xE7] = Instruction{.cycles = 5, .execute = &CPU::ISC, .fetch = &CPU::ZeroPage};
instructions[0xF7] = Instruction{.cycles = 6, .execute = &CPU::ISC, .fetch = &CPU::ZeroPageX};
instructions[0xEF] = Instruction{.cycles = 6, .execute = &CPU::ISC, .fetch = &CPU::Absolute};
instructions[0xFF] = Instruction{.cycles = 7, .execute = &CPU::ISC, .fetch = &CPU::AbsoluteX};
instructions[0xFB] = Instruction{.cycles = 7, .execute = &CPU::ISC, .fetch = &CPU::AbsoluteY};
instructions[0xE3] = Instruction{.cycles = 8, .execute = &CPU::ISC, .fetch = &CPU::IndirectX};
instructions[0xF3] = Instruction{.cycles = 8, .execute = &CPU::ISC, .fetch = &CPU::IndirectY};
instructions[0x0B] = Instruction{.name = "ANC", .cycles = 2, .execute = &CPU::ANC, .fetch = &CPU::Immediate};
instructions[0x2B] = Instruction{.name = "ANC", .cycles = 2, .execute = &CPU::ANC, .fetch = &CPU::Immediate};
instructions[0x4B] = Instruction{.name = "ALR", .cycles = 0, .execute = &CPU::ALR, .fetch = &CPU::Immediate};
instructions[0x6B] = Instruction{.name = "ARR", .cycles = 0, .execute = &CPU::ARR, .fetch = &CPU::Immediate};
instructions[0xCB] = Instruction{.name = "AXS", .cycles = 0, .execute = &CPU::AXS, .fetch = &CPU::Immediate};
instructions[0x0B] = Instruction{.cycles = 2, .execute = &CPU::ANC, .fetch = &CPU::Immediate};
instructions[0x2B] = Instruction{.cycles = 2, .execute = &CPU::ANC, .fetch = &CPU::Immediate};
instructions[0x4B] = Instruction{.cycles = 0, .execute = &CPU::ALR, .fetch = &CPU::Immediate};
instructions[0x6B] = Instruction{.cycles = 0, .execute = &CPU::ARR, .fetch = &CPU::Immediate};
instructions[0xCB] = Instruction{.cycles = 0, .execute = &CPU::AXS, .fetch = &CPU::Immediate};
// Unused by NES
instructions[0x9C] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9E] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x8B] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x93] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9B] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9F] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xBB] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x02] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x12] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x22] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x32] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x42] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x52] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x62] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x72] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x92] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xB2] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xD2] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xF2] = Instruction{.name = "ILL", .cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
}
void CPU::Reset()
{
uint8_t startAddressLsb = ReadMemory(RESET_VECTOR_LSB);
uint8_t startAddressMsb = ReadMemory(RESET_VECTOR_MSB);
uint16_t startAddress = ComposeAddress(startAddressMsb, startAddressLsb);
pc = startAddress;
cycles = 7u;
status.SetByte(0x34u);
sp = 0xFDu;
memset(ram, 0, RAM_SIZE);
instructions[0x9C] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9E] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x8B] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x93] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9B] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x9F] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xBB] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x02] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x12] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x22] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x32] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x42] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x52] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x62] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x72] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0x92] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xB2] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xD2] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
instructions[0xF2] = Instruction{.cycles = 0, .execute = &CPU::NOP, .fetch = &CPU::Implicit};
}
void CPU::StackPush(uint8_t val)
@ -348,135 +329,179 @@ uint8_t CPU::StackPop()
return ReadMemory(address);
}
uint64_t CPU::Cycle()
void CPU::WriteMemory(uint16_t address, uint8_t value)
{
if (nes->nmi)
// First five bits of address determines its mapping
switch ((address & 0xF800u) >> 11u)
{
NMI();
// RAM and mirrors
case 0x00:
case 0x01:
case 0x02:
case 0x03:
{
uint16_t translatedAddress = address & 0x7FFu;
ram[translatedAddress] = value;
break;
}
// SRAM and mirrors
case 0x0C:
case 0x0D:
case 0x0E:
case 0x0F:
{
uint16_t translatedAddress = address & 0x1FFFu;
sram[translatedAddress] = value;
break;
}
// ROM (Low) and mirrors
case 0x10:
case 0x11:
case 0x12:
case 0x13:
case 0x14:
case 0x15:
case 0x16:
case 0x17:
{
uint16_t translatedAddress = address & 0x3FFFu;
romLow[translatedAddress] = value;
break;
}
// ROM (High) and mirrors
case 0x18:
case 0x19:
case 0x1A:
case 0x1B:
case 0x1C:
case 0x1D:
case 0x1E:
case 0x1F:
{
uint16_t translatedAddress = address & 0x3FFFu;
romHigh[translatedAddress] = value;
break;
}
}
}
uint8_t CPU::ReadMemory(uint16_t address)
{
uint8_t byte{};
switch ((address & 0xF800u) >> 11u)
{
// RAM and mirrors
case 0x00:
case 0x01:
case 0x02:
case 0x03:
{
uint16_t translatedAddress = address & 0x7FFu;
byte = ram[translatedAddress];
break;
}
// SRAM and mirrors
case 0x0C:
case 0x0D:
case 0x0E:
case 0x0F:
{
uint16_t translatedAddress = address & 0x1FFFu;
byte = sram[translatedAddress];
break;
}
// ROM (Low) and mirrors
case 0x10:
case 0x11:
case 0x12:
case 0x13:
case 0x14:
case 0x15:
case 0x16:
case 0x17:
{
uint16_t translatedAddress = address & 0x3FFFu;
byte = romLow[translatedAddress];
break;
}
// ROM (High) and mirrors
case 0x18:
case 0x19:
case 0x1A:
case 0x1B:
case 0x1C:
case 0x1D:
case 0x1E:
case 0x1F:
{
uint16_t translatedAddress = address & 0x3FFFu;
byte = romHigh[translatedAddress];
break;
}
}
return byte;
}
void CPU::LoadRom(const char* filename)
{
std::ifstream file(filename, std::ios::binary | std::ios::ate);
if (file.is_open())
{
std::streampos size = file.tellg();
char* buffer = new char[size];
file.seekg(0x10, std::ios::beg);
file.read(buffer, size);
file.close();
for (long i = 0; i < 0x4000; ++i)
{
WriteMemory(0x8000 + i, buffer[i]);
WriteMemory(0xC000 + i, buffer[i]);
}
delete[] buffer;
}
}
void CPU::Cycle()
{
opcode = ReadMemory(pc);
//Log();
#ifndef NDEBUG
Log(opcode, pc);
#endif
pageBoundaryCrossed = false;
prevCycles = cycles;
((*this).*(instructions[opcode].fetch))();
((*this).*(instructions[opcode].execute))();
cycles += instructions[opcode].cycles;
return cycles - prevCycles;
}
void CPU::NMI()
void CPU::Log(uint8_t instruction, uint16_t pc)
{
nes->nmi = false;
uint8_t pcMsb = (pc & 0xFF00u) >> 8u;
uint8_t pcLsb = pc & 0xFFu;
StackPush(pcMsb);
StackPush(pcLsb);
Status statusCopy = status;
statusCopy.b1 = 1u;
statusCopy.b0 = 0u;
StackPush(statusCopy.GetByte());
pcMsb = ReadMemory(NMI_VECTOR_MSB);
pcLsb = ReadMemory(NMI_VECTOR_LSB);
pc = ComposeAddress(pcMsb, pcLsb);
}
void CPU::Log()
{
Instruction& instruction = instructions[opcode];
printf("%04X ", pc);
if (instruction.fetch == &CPU::Implicit)
{
printf("%02X %s ", ReadMemory(pc), instruction.name);
}
else if (instruction.fetch == &CPU::Immediate)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s #$%02X ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::ZeroPage)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s $%02X ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::ZeroPageX)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s $%02X,X ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::ZeroPageY)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s $%02X,Y ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::IndirectX)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s ($%02X,X) ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::Relative)
{
uint8_t op = ReadMemory(pc);
int8_t operand = ReadMemory(pc + 1);
uint16_t address = pc + 2 + operand;
printf("%02X %02X %s $%04X ", op, (uint8_t)operand, instruction.name, address);
}
else if (instruction.fetch == &CPU::IndirectY)
{
uint8_t op = ReadMemory(pc);
uint8_t operand = ReadMemory(pc + 1);
printf("%02X %02X %s ($%02X),Y ", op, operand, instruction.name, operand);
}
else if (instruction.fetch == &CPU::Absolute)
{
uint8_t op = ReadMemory(pc);
uint8_t operand1 = ReadMemory(pc + 1);
uint8_t operand2 = ReadMemory(pc + 2);
printf("%02X %02X %02X %s $%02X%02X ", op, operand1, operand2, instruction.name, operand2, operand1);
}
else if (instruction.fetch == &CPU::Indirect)
{
uint8_t op = ReadMemory(pc);
uint8_t operand1 = ReadMemory(pc + 1);
uint8_t operand2 = ReadMemory(pc + 2);
printf("%02X %02X %02X %s ($%02X%02X) ", op, operand1, operand2, instruction.name, operand2, operand1);
}
else if (instruction.fetch == &CPU::AbsoluteX)
{
uint8_t op = ReadMemory(pc);
uint8_t operand1 = ReadMemory(pc + 1);
uint8_t operand2 = ReadMemory(pc + 2);
printf("%02X %02X %02X %s $%02X%02X,X ", op, operand1, operand2, instruction.name, operand2, operand1);
}
else if (instruction.fetch == &CPU::AbsoluteY)
{
uint8_t op = ReadMemory(pc);
uint8_t operand1 = ReadMemory(pc + 1);
uint8_t operand2 = ReadMemory(pc + 2);
printf("%02X %02X %02X %s $%02X%02X,Y ", op, operand1, operand2, instruction.name, operand2, operand1);
}
printf("A:%02X X:%02X Y:%02X P:%02X SP:%02X CYC:%lu\n", acc, x, y, status.GetByte(), sp, cycles);
printf("A:%02X X:%02X Y:%02X P:%02X SP:%02X PPU:000,000 CYC:%lu\n", acc, x, y, status.GetByte(), sp, cycles);
}
bool CPU::TestBits(uint8_t value, uint8_t bits)
@ -500,13 +525,3 @@ uint16_t CPU::ComposeAddress(uint8_t msb, uint8_t lsb)
{
return (msb << 8u) | lsb;
}
void CPU::WriteMemory(uint16_t address, uint8_t value)
{
nes->Write(BusSource::CPU, address, value);
}
uint8_t CPU::ReadMemory(uint16_t address)
{
return nes->Read(BusSource::CPU, address);
}

33
Source/CPU/CPU.hpp
View File

@ -7,15 +7,13 @@
const unsigned int INSTRUCTION_COUNT = 256;
const unsigned int RAM_SIZE = 2048;
const unsigned int SRAM_SIZE = 8192;
const unsigned int ROM_SIZE = 16384;
const unsigned int IRQ_VECTOR_MSB = 0xFFFF;
const unsigned int IRQ_VECTOR_LSB = 0xFFFE;
class NES;
class Status
{
friend class NES;
public:
void SetByte(uint8_t byte)
{
@ -50,7 +48,6 @@ class CPU;
class Instruction
{
public:
char const* name;
uint8_t cycles;
using CpuFunc = void (CPU::*)();
@ -63,18 +60,16 @@ class CPU
{
public:
CPU();
uint64_t Cycle();
void Log();
void Reset();
void NMI();
void LoadRom(const char* filename);
void Cycle();
void Log(uint8_t instruction, uint16_t pc);
private:
void StackPush(uint8_t val);
uint8_t StackPop();
void WriteMemory(uint16_t address, uint8_t value);
uint8_t ReadMemory(uint16_t address);
friend class NES;
void StackPush(uint8_t val);
uint8_t StackPop();
// --------------- HELPERS --------------- //
static bool TestBits(uint8_t value, uint8_t bits);
@ -224,15 +219,17 @@ public:
// Machine features
uint8_t ram[RAM_SIZE]{};
uint8_t sram[SRAM_SIZE]{};
uint16_t pc{};
uint8_t sp{};
uint8_t romLow[ROM_SIZE]{};
uint8_t romHigh[ROM_SIZE]{};
uint16_t pc = 0xC000;
uint8_t sp = 0xFD;
uint8_t acc{};
uint8_t x{};
uint8_t y{};
Status status{};
uint64_t prevCycles{};
uint64_t cycles{};
uint64_t cycles = 7;
bool irq{};
bool nmi{};
// Emulator variables
bool pageBoundaryCrossed{};
@ -241,6 +238,6 @@ public:
uint8_t fetchedByte{};
Instruction instructions[INSTRUCTION_COUNT]{};
NES* nes;
};

77
Source/CPU/Instructions.cpp
View File

@ -1,11 +1,9 @@
#include "CPU/CPU.hpp"
#include "NES.hpp"
// --------------- ARITHMETIC --------------- //
void CPU::ADC()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
uint16_t tempSum = acc + fetchedByte;
tempSum += status.carry;
@ -29,7 +27,6 @@ void CPU::ADC()
void CPU::SBC()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
uint16_t tempDiff = acc - fetchedByte;
tempDiff -= (1u - status.carry);
@ -54,7 +51,6 @@ void CPU::SBC()
void CPU::CMP()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
status.carry = (acc >= fetchedByte) ? 1u : 0u;
status.zero = (acc == fetchedByte) ? 1u : 0u;
status.negative = (IsNegative(acc - fetchedByte)) ? 1u : 0u;
@ -64,7 +60,6 @@ void CPU::CMP()
void CPU::CPX()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
status.carry = (x >= fetchedByte) ? 1u : 0u;
status.zero = (x == fetchedByte) ? 1u : 0u;
status.negative = (IsNegative(x - fetchedByte)) ? 1u : 0u;
@ -72,7 +67,6 @@ void CPU::CPX()
void CPU::CPY()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
status.carry = (y >= fetchedByte) ? 1u : 0u;
status.zero = (y == fetchedByte) ? 1u : 0u;
status.negative = (IsNegative(y - fetchedByte)) ? 1u : 0u;
@ -164,10 +158,9 @@ void CPU::BEQ()
// --------------- INCREMENT/DECREMENT --------------- //
void CPU::INC()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
++fetchedByte;
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
status.zero = fetchedByte ? 0u : 1u;
status.negative = (IsNegative(fetchedByte)) ? 1u : 0u;
@ -191,10 +184,9 @@ void CPU::INY()
void CPU::DEC()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
--fetchedByte;
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
status.zero = fetchedByte ? 0u : 1u;
status.negative = (IsNegative(fetchedByte)) ? 1u : 0u;
@ -248,7 +240,6 @@ void CPU::RTS()
// --------------- LOAD/STORE --------------- //
void CPU::LDA()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
cycles += (pageBoundaryCrossed) ? 1u : 0u;
acc = fetchedByte;
@ -259,7 +250,6 @@ void CPU::LDA()
void CPU::LDX()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
cycles += (pageBoundaryCrossed) ? 1u : 0u;
x = fetchedByte;
@ -270,7 +260,6 @@ void CPU::LDX()
void CPU::LDY()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
cycles += (pageBoundaryCrossed) ? 1u : 0u;
y = fetchedByte;
@ -281,25 +270,23 @@ void CPU::LDY()
void CPU::STA()
{
nes->Write(BusSource::CPU, fetchedAddress, acc);
WriteMemory(fetchedAddress, acc);
}
void CPU::STX()
{
nes->Write(BusSource::CPU, fetchedAddress, x);
WriteMemory(fetchedAddress, x);
}
void CPU::STY()
{
nes->Write(BusSource::CPU, fetchedAddress, y);
WriteMemory(fetchedAddress, y);
}
// --------------- LOGICAL --------------- //
void CPU::AND()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
acc &= fetchedByte;
cycles += (pageBoundaryCrossed) ? 1u : 0u;
@ -309,7 +296,6 @@ void CPU::AND()
void CPU::EOR()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
acc ^= fetchedByte;
cycles += (pageBoundaryCrossed) ? 1u : 0u;
@ -319,7 +305,6 @@ void CPU::EOR()
void CPU::ORA()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
acc |= fetchedByte;
cycles += (pageBoundaryCrossed) ? 1u : 0u;
@ -329,7 +314,6 @@ void CPU::ORA()
void CPU::BIT()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
status.zero = (acc & fetchedByte) ? 0u : 1u;
status.overflow = (TestBits(fetchedByte, (1u << 6u))) ? 1u : 0u;
status.negative = (IsNegative(fetchedByte)) ? 1u : 0u;
@ -339,15 +323,6 @@ void CPU::BIT()
// --------------- SHIFTS --------------- //
void CPU::ASL()
{
if (instructions[opcode].fetch == &CPU::Implicit)
{
fetchedByte = acc;
}
else
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
}
// Set carry to fetchedByte of MSB pre-shift
if (TestBits(fetchedByte, 0x80))
{
@ -369,21 +344,12 @@ void CPU::ASL()
}
else
{
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
}
}
void CPU::LSR()
{
if (instructions[opcode].fetch == &CPU::Implicit)
{
fetchedByte = acc;
}
else
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
}
// Set carry to fetchedByte of LSB pre-shift
if (TestBits(fetchedByte, 0x01))
{
@ -405,21 +371,12 @@ void CPU::LSR()
}
else
{
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
}
}
void CPU::ROL()
{
if (instructions[opcode].fetch == &CPU::Implicit)
{
fetchedByte = acc;
}
else
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
}
uint8_t oldCarry = status.carry;
// Set carry to fetchedByte of MSB pre-shift
@ -449,21 +406,12 @@ void CPU::ROL()
}
else
{
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
}
}
void CPU::ROR()
{
if (instructions[opcode].fetch == &CPU::Implicit)
{
fetchedByte = acc;
}
else
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
}
uint8_t oldCarry = status.carry;
// Set carry to fetchedByte of LSB pre-shift
@ -493,7 +441,7 @@ void CPU::ROR()
}
else
{
nes->Write(BusSource::CPU, fetchedAddress, fetchedByte);
WriteMemory(fetchedAddress, fetchedByte);
}
}
@ -583,8 +531,8 @@ void CPU::BRK()
StackPush(statusCopy.GetByte());
pcMsb = nes->Read(BusSource::CPU, IRQ_VECTOR_MSB);
pcLsb = nes->Read(BusSource::CPU, IRQ_VECTOR_LSB);
pcMsb = ReadMemory(IRQ_VECTOR_MSB);
pcLsb = ReadMemory(IRQ_VECTOR_LSB);
pc = ComposeAddress(pcMsb, pcLsb);
}
@ -667,7 +615,7 @@ void CPU::SAX()
{
uint8_t byte = acc & x;
nes->Write(BusSource::CPU, fetchedAddress, byte);
WriteMemory(fetchedAddress, byte);
}
void CPU::DCP()
@ -742,7 +690,6 @@ void CPU::ARR()
void CPU::AXS()
{
fetchedByte = nes->Read(BusSource::CPU, fetchedAddress);
x = (acc & x) - fetchedByte;
status.negative = (IsNegative(x)) ? 1u : 0u;

58
Source/Cartridge.cpp
View File

@ -1,58 +0,0 @@
#include "Cartridge.hpp"
#include <fstream>
#include <iostream>
#include <string>
const unsigned int HEADER_SIZE = 16u;
#pragma pack(push, 1)
struct Header
{
uint8_t string[4];
uint8_t prgSize;
uint8_t chrSize;
uint8_t flags6;
uint8_t flags7;
uint8_t flags8;
uint8_t flags9;
uint8_t flags10;
uint8_t padding[5];
};
#pragma pack(pop)
void Cartridge::Load(char const* filename)
{
std::ifstream file(filename, std::ios::binary);
if (file.is_open())
{
char buf[HEADER_SIZE];
file.read(buf, HEADER_SIZE);
auto header = reinterpret_cast<Header*>(buf);
// Trainer
if (header->flags6 & 0x4)
{
char trainerBuf[512];
file.read(trainerBuf, 512);
}
uint32_t prgSize = header->prgSize * 16384;
prgROM.resize(prgSize);
file.read(reinterpret_cast<char*>(prgROM.data()), prgSize);
uint32_t chrSize = header->chrSize * 8192;
if (chrSize > 0)
{
chrROM.resize(chrSize);
file.read(reinterpret_cast<char*>(chrROM.data()), chrSize);
}
file.close();
}
}

18
Source/Cartridge.hpp
View File

@ -1,18 +0,0 @@
#pragma once
#include <cstdint>
#include <vector>
class Cartridge
{
public:
void Load(char const* filename);
private:
friend class NES;
std::vector<uint8_t> prgROM;
std::vector<uint8_t> chrROM;
};

40
Source/Input.cpp
View File

@ -1,40 +0,0 @@
#include "Input.hpp"
void Input::Strobe(uint8_t* but)
{
if (strobe)
{
for (int i = 0; i < 8; ++i)
{
buttons[i] = but[i];
}
}
}
uint8_t Input::Poll()
{
uint8_t buttonState;
// Strobe set - return state of A button
if (strobe)
{
buttonState = buttons[Buttons::A];
}
// All 8 bits read - return 1u
else if (buttonIndex > Buttons::Right)
{
buttonState = 1u;
}
// Return next bit
else
{
buttonState = buttons[buttonIndex];
++buttonIndex;
}
return buttonState;
}

32
Source/Input.hpp
View File

@ -1,32 +0,0 @@
#pragma once
#include <cstdint>
#include <cstdio>
enum Buttons
{
A = 0,
B = 1,
Select = 2,
Start = 3,
Up = 4,
Down = 5,
Left = 6,
Right = 7
};
class Input
{
public:
void Strobe(uint8_t* but);
uint8_t Poll();
private:
friend class NES;
bool strobe{};
uint8_t buttonIndex{};
uint8_t buttons[8]{};
};

15
Source/Main.cpp
View File

@ -1,18 +1,21 @@
#include <iostream>
#include "NES.hpp"
#include "CPU/CPU.hpp"
int main(int argc, char** argv)
{
if (argc != 2)
{
std::cerr << "Usage: " << argv[0] << " <ROM>\n";
std::cerr << "Usage: " << argv[0] << "<ROM>\n";
std::exit(EXIT_FAILURE);
}
char const* filename = argv[1];
CPU cpu;
NES nes;
nes.InsertCartridge(filename);
nes.Run();
cpu.LoadRom("nestest.nes");
while (true)
{
cpu.Cycle();
}
}

374
Source/NES.cpp
View File

@ -1,374 +0,0 @@
#include "NES.hpp"
#include <chrono>
const unsigned int VIDEO_SCALE = 4u;
const unsigned int WINDOW_WIDTH = VIDEO_WIDTH * VIDEO_SCALE;
const unsigned int WINDOW_HEIGHT = VIDEO_HEIGHT * VIDEO_SCALE;
const unsigned int VIDEO_PITCH = VIDEO_WIDTH * 4u;
const unsigned int PPU_CYCLES_PER_CPU_CYCLE = 3u;
void DrawDebugLines(uint32_t* buffer)
{
for (int y = 0; y < VIDEO_HEIGHT; ++y)
{
for (int x = 0; x < VIDEO_WIDTH; ++x)
{
if (x == 0 || y == 0)
{
continue;
}
if (x % 8 == 0u)
{
buffer[y * VIDEO_WIDTH + x] = 0xFF00FFFFu;
}
if (x % 32 == 0u)
{
buffer[y * VIDEO_WIDTH + x] = 0xFF0000FFu;
}
if (y % 8 == 0u)
{
buffer[y * VIDEO_WIDTH + x] = 0xFF00FFFFu;
}
if (y % 32 == 0u)
{
buffer[y * VIDEO_WIDTH + x] = 0xFF0000FFu;
}
}
}
}
NES::NES()
: cpu(std::make_unique<CPU>()),
ppu(std::make_unique<PPU>()),
cartridge(std::make_unique<Cartridge>()),
platform(std::make_unique<Platform>("NES", WINDOW_WIDTH, WINDOW_HEIGHT, VIDEO_WIDTH, VIDEO_HEIGHT)),
input(std::make_unique<Input>())
{
ppu->nes = this;
palette[0] = Color(84, 84, 84);
palette[1] = Color(0, 30, 116);
palette[2] = Color(8, 16, 144);
palette[3] = Color(48, 0, 136);
palette[4] = Color(68, 0, 100);
palette[5] = Color(92, 0, 48);
palette[6] = Color(84, 4, 0);
palette[7] = Color(60, 24, 0);
palette[8] = Color(32, 42, 0);
palette[9] = Color(8, 58, 0);
palette[10] = Color(0, 64, 0);
palette[11] = Color(0, 60, 0);
palette[12] = Color(0, 50, 60);
palette[13] = Color(0, 0, 0);
palette[14] = Color(0, 0, 0);
palette[15] = Color(0, 0, 0);
palette[16] = Color(152, 150, 152);
palette[17] = Color(8, 76, 196);
palette[18] = Color(48, 50, 236);
palette[19] = Color(92, 30, 228);
palette[20] = Color(136, 20, 176);
palette[21] = Color(160, 20, 100);
palette[22] = Color(152, 34, 32);
palette[23] = Color(120, 60, 0);
palette[24] = Color(84, 90, 0);
palette[25] = Color(40, 114, 0);
palette[26] = Color(8, 124, 0);
palette[27] = Color(0, 118, 40);
palette[28] = Color(0, 102, 120);
palette[29] = Color(0, 0, 0);
palette[30] = Color(0, 0, 0);
palette[31] = Color(0, 0, 0);
palette[32] = Color(236, 238, 236);
palette[33] = Color(76, 154, 236);
palette[34] = Color(120, 124, 236);
palette[35] = Color(176, 98, 236);
palette[36] = Color(228, 84, 236);
palette[37] = Color(236, 88, 180);
palette[38] = Color(236, 106, 100);
palette[39] = Color(212, 136, 32);
palette[40] = Color(160, 170, 0);
palette[41] = Color(116, 196, 0);
palette[42] = Color(76, 208, 32);
palette[43] = Color(56, 204, 108);
palette[44] = Color(56, 180, 204);
palette[45] = Color(60, 60, 60);
palette[46] = Color(0, 0, 0);
palette[47] = Color(0, 0, 0);
palette[48] = Color(236, 238, 236);
palette[49] = Color(168, 204, 236);
palette[50] = Color(188, 188, 236);
palette[51] = Color(212, 178, 236);
palette[52] = Color(236, 174, 236);
palette[53] = Color(236, 174, 212);
palette[54] = Color(236, 180, 176);
palette[55] = Color(228, 196, 144);
palette[56] = Color(204, 210, 120);
palette[57] = Color(180, 222, 120);
palette[58] = Color(168, 226, 144);
palette[59] = Color(152, 226, 180);
palette[60] = Color(160, 214, 228);
palette[61] = Color(160, 162, 160);
palette[62] = Color(0, 0, 0);
palette[63] = Color(0, 0, 0);
}
void NES::InsertCartridge(char const* filename)
{
cartridge->Load(filename);
cpu->nes = this;
cpu->Reset();
}
void NES::Run()
{
uint8_t buttons[8]{};
while (!platform->ProcessInput(buttons))
{
input->Strobe(buttons);
uint64_t cpuCycles = cpu->Cycle();
for (auto i = 0; i < cpuCycles * PPU_CYCLES_PER_CPU_CYCLE; ++i)
{
ppu->Tick();
}
if (ppu->currentScanline == 261)
{
//DrawDebugLines(ppu->video);
platform->Update(ppu->video, VIDEO_PITCH);
}
}
}
void NES::Write(BusSource source, uint16_t address, uint8_t value)
{
switch (source)
{
case BusSource::CPU:
{
// CPU RAM and Mirrors
if (address < 0x2000u)
{
uint16_t index = address & 0x7FFu;
cpu->ram[index] = value;
}
// PPU Registers and Mirrors
else if (address < 0x4000u)
{
auto index = static_cast<PPU::Register>(address % 8u);
ppu->WriteRegister(index, value);
}
// APU and IO
else if (address < 0x4020u)
{
uint16_t index = address & 0x1Fu;
// PPU OAM
if (index == 0x14u)
{
uint8_t addrMsb = value;
for (uint16_t addrLsb = 0x00; addrLsb <= 0xFF; ++addrLsb)
{
uint16_t addr = (addrMsb << 8u) | addrLsb;
ppu->oam[ppu->regOAMADDR + addrLsb] = Read(BusSource::CPU, addr);
}
}
// Controller
else if (index == 0x16u)
{
if (value & 0x1u)
{
input->strobe = true;
}
else
{
input->strobe = false;
input->buttonIndex = 0u;
}
}
}
// Expansion I/O
else if (address < 0x6000u)
{
}
// SRAM
else if (address < 0x8000u)
{
uint16_t index = address & 0x1FFFu;
cpu->sram[index] = value;
}
break;
}
case BusSource::PPU:
{
// Name Tables and Attribute Tables
if (address > 0x2000u && address < 0x3000u)
{
uint16_t index = address & 0x3FFu;
ppu->ram[index] = value;
}
// Mirrors of $2000 - $2EFF
else if (address < 0x3F00u)
{
uint16_t index = address & 0xEFFu;
ppu->ram[index] = value;
}
// Palette RAM Indexes and Mirrors
else if (address < 0x3F20u)
{
uint8_t index = (address & 0x1Cu) >> 2u;
uint8_t entry = address & 0x03u;
ppu->palette[index][entry] = value;
}
break;
}
}
}
uint8_t NES::Read(BusSource source, uint16_t address)
{
uint8_t byte{};
switch (source)
{
case BusSource::CPU:
{
// CPU RAM and Mirrors
if (address < 0x2000u)
{
uint16_t index = address & 0x7FFu;
byte = cpu->ram[index];
}
// PPU Registers and Mirrors
else if (address < 0x4000u)
{
auto index = static_cast<PPU::Register>(address % 8u);
byte = ppu->ReadRegister(index);
}
// APU and IO
else if (address < 0x4020u)
{
uint16_t index = address & 0x1Fu;
// Controller
if (index == 0x16u)
{
byte = input->Poll();
}
}
// Expansion I/O
else if (address < 0x6000u)
{
}
// SRAM
else if (address < 0x8000u)
{
uint16_t index = address & 0x1FFFu;
byte = cpu->sram[index];
}
// CHR-ROM
else if (address < 0xC000u)
{
uint16_t index = address & 0x3FFFu;
byte = cartridge->chrROM[index];
}
// PRG-ROM
else if (address < 0xFFFFu)
{
uint16_t index = address & 0x3FFFu;
byte = cartridge->prgROM[index];
}
break;
}
case BusSource::PPU:
{
// Cartridge ROM
if (address < 0x2000u)
{
uint16_t index = address & 0x1FFFu;
byte = cartridge->chrROM[index];
}
// Name Tables and Attribute Tables
else if (address < 0x3000u)
{
uint16_t index = address & 0x3FFu;
byte = ppu->ram[index];
}
// Mirrors of $2000 - $2EFF
else if (address < 0x3F00u)
{
uint16_t index = address & 0xEFFu;
byte = ppu->ram[index];
}
// Palette RAM Indexes and Mirrors
else if (address < 0x3F20u)
{
uint8_t index = address & 0x0Cu;
uint8_t entry = address & 0x03u;
byte = ppu->palette[index][entry];
}
break;
}
}
return byte;
}

54
Source/NES.hpp
View File

@ -1,54 +0,0 @@
#pragma once
#include "Cartridge.hpp"
#include "CPU/CPU.hpp"
#include "Input.hpp"
#include "Platform.hpp"
#include "PPU/PPU.hpp"
#include <memory>
struct Color
{
Color()
: r(0), g(0), b(0), a(0)
{
}
Color(uint8_t r, uint8_t g, uint8_t b)
: r(r), g(g), b(b), a(255)
{}
uint8_t r, g, b, a;
uint32_t GetValue()
{
return (r << 24u) | (g << 16u) | (b << 8u) | a;
}
};
enum class BusSource
{
CPU,
PPU
};
class NES
{
public:
NES();
void InsertCartridge(char const* filename);
void Run();
void Write(BusSource source, uint16_t address, uint8_t value);
uint8_t Read(BusSource source, uint16_t address);
std::unique_ptr<CPU> cpu;
std::unique_ptr<PPU> ppu;
std::unique_ptr<Cartridge> cartridge;
std::unique_ptr<Platform> platform;
std::unique_ptr<Input> input;
bool nmi{};
Color palette[64];
};

703
Source/PPU/PPU.cpp
View File

@ -1,703 +0,0 @@
#include "PPU.hpp"
#include "NES.hpp"
const unsigned int BG_PALETTE_START_ADDRESS = 0x3F00u;
const unsigned int PATTERN_TABLE_0_START = 0x0000u;
const unsigned int PATTERN_TABLE_1_START = 0x1000u;
const unsigned int ATTRIBUTE_TABLE_START = 0x23C0u;
unsigned char reverse(uint8_t b)
{
b = (b & 0xF0u) >> 4u | (b & 0x0Fu) << 4u;
b = (b & 0xCCu) >> 2u | (b & 0x33u) << 2u;
b = (b & 0xAAu) >> 1u | (b & 0x55u) << 1u;
return b;
}
bool CheckBit(uint32_t value, uint32_t bit)
{
return (value & bit) == bit;
}
PPU::PPU()
{
// Visible Frame
{
for (int scanline = 0; scanline <= 239; ++scanline)
{
// Data fetching
for (int cycle = 1; cycle <= 256; cycle += 8)
{
events[scanline][cycle + 0] |= Event::FETCH_NT;
events[scanline][cycle + 2] |= Event::FETCH_AT;
events[scanline][cycle + 4] |= Event::FETCH_PT_LOW;
events[scanline][cycle + 6] |= Event::FETCH_PT_HIGH;
}
// Incrementing Hori(V)
for (int cycle = 8; cycle <= 256; cycle += 8)
{
events[scanline][cycle] |= Event::INCREMENT_TILE_X;
}
// Draw and shift
for (int cycle = 2; cycle <= 257; ++cycle)
{
events[scanline][cycle] |= Event::DRAW | Event::SHIFT_BACKGROUND;
}
// Reload shift registers
for (int cycle = 9; cycle <= 257; cycle += 8)
{
events[scanline][cycle] |= Event::LOAD_BACKGROUND;
}
// Inc Vert(v)
events[scanline][256] |= Event::INCREMENT_TILE_Y;
// Hori(v) = Hori(T)
events[scanline][257] |= Event::SET_TILE_X;
// Data fetching
for (int cycle = 321; cycle <= 336; cycle += 8)
{
events[scanline][cycle + 0] |= Event::FETCH_NT;
events[scanline][cycle + 2] |= Event::FETCH_AT;
events[scanline][cycle + 4] |= Event::FETCH_PT_LOW;
events[scanline][cycle + 6] |= Event::FETCH_PT_HIGH;
}
// Shift
for (int cycle = 322; cycle <= 337; ++cycle)
{
events[scanline][cycle] |= Event::SHIFT_BACKGROUND;
}
// Reload shift registers
for (int cycle = 329; cycle <= 337; cycle += 8)
{
events[scanline][cycle] |= Event::LOAD_BACKGROUND;
}
events[scanline][328] |= Event::INCREMENT_TILE_X;
events[scanline][336] |= Event::INCREMENT_TILE_X;
// Unused Fetches
events[scanline][337] |= Event::FETCH_NT;
events[scanline][339] |= Event::FETCH_NT;
}
}
// VBlank
{
events[241][1] |= Event::SET_VBLANK;
}
// Pre-render
{
// Clear VBlank, Sprite0 Hit, and Sprite Overflow
events[261][1] |= Event::CLEAR_FLAGS;
// Data fetching
for (int cycle = 1; cycle <= 256; cycle += 8)
{
events[261][cycle + 0] |= Event::FETCH_NT;
events[261][cycle + 2] |= Event::FETCH_AT;
events[261][cycle + 4] |= Event::FETCH_PT_LOW;
events[261][cycle + 6] |= Event::FETCH_PT_HIGH;
}
// Incrementing Hori(V)
for (int cycle = 8; cycle <= 256; cycle += 8)
{
events[261][cycle] |= Event::INCREMENT_TILE_X;
}
// Shift
for (int cycle = 2; cycle <= 257; ++cycle)
{
events[261][cycle] |= Event::SHIFT_BACKGROUND;
}
// Reload shift registers
for (int cycle = 9; cycle <= 257; cycle += 8)
{
events[261][cycle] |= Event::LOAD_BACKGROUND;
}
// Inc Vert(v)
events[261][256] |= Event::INCREMENT_TILE_Y;
// Hori(v) = Hori(t)
events[261][257] |= Event::SET_TILE_X;
// Vert(v) = Vert(t)
for (int cycle = 280; cycle <= 304; ++cycle)
{
events[261][cycle] |= Event::SET_TILE_Y;
}
// Data fetching
for (int cycle = 321; cycle <= 336; cycle += 8)
{
events[261][cycle + 0] |= Event::FETCH_NT;
events[261][cycle + 2] |= Event::FETCH_AT;
events[261][cycle + 4] |= Event::FETCH_PT_LOW;
events[261][cycle + 6] |= Event::FETCH_PT_HIGH;
}
// Shift
for (int cycle = 322; cycle <= 337; ++cycle)
{
events[261][cycle] |= Event::SHIFT_BACKGROUND;
}
// Reload shift registers
for (int cycle = 329; cycle <= 337; cycle += 8)
{
events[261][cycle] |= Event::LOAD_BACKGROUND;
}
events[261][328] |= Event::INCREMENT_TILE_X;
events[261][336] |= Event::INCREMENT_TILE_X;
// Unused Fetches
events[261][337] |= Event::FETCH_NT;
events[261][339] |= Event::FETCH_NT;
}
}
void PPU::Tick()
{
int event = events[currentScanline][currentCycle];
if (CheckBit(event, Event::DRAW))
{
Draw();
}
if (CheckBit(event, Event::SHIFT_BACKGROUND))
{
ShiftBG();
}
if (CheckBit(event, Event::FETCH_NT))
{
FetchNT();
}
else if (CheckBit(event, Event::FETCH_AT))
{
FetchAT();
}
else if (CheckBit(event, Event::FETCH_PT_LOW))
{
FetchPTLow();
}
else if (CheckBit(event, Event::FETCH_PT_HIGH))
{
FetchPTHigh();
}
if (CheckBit(event, Event::LOAD_BACKGROUND))
{
LoadBackground();
}
if (CheckBit(event, Event::SET_TILE_X))
{
SetTileX();
}
else if (CheckBit(event, Event::SET_TILE_Y))
{
SetTileY();
}
if (CheckBit(event, Event::INCREMENT_TILE_Y))
{
IncrementTileY();
}
else if (CheckBit(event, Event::INCREMENT_TILE_X))
{
IncrementTileX();
}
if (CheckBit(event, Event::SET_VBLANK))
{
SetVBlank();
}
else if (CheckBit(event, Event::CLEAR_FLAGS))
{
ClearFlags();
}
++currentCycle;
// Odd frame, skip
if (currentScanline == 261 && currentCycle == 340 && (frameNumber % 2))
{
currentScanline = 0;
currentCycle = 0;
++frameNumber;
}
else if (currentCycle == 341)
{
currentCycle = 0;
++currentScanline;
if (currentScanline == 262)
{
currentScanline = 0;
++frameNumber;
}
}
}
void PPU::WriteRegister(Register reg, uint8_t value)
{
switch (reg)
{
case Register::PPUCTRL:
{
regPPUCTRL.SetByte(value);
// yyy NNYY YYYX XXXX
// t: --- BA-- ---- ---- = d: ---- --BA
tempAddress.nametableY = (value & 0x2u) >> 1u;
tempAddress.nametableX = (value & 0x1u) >> 1u;
break;
}
case Register::PPUMASK:
{
regPPUMASK.SetByte(value);
break;
}
case Register::OAMADDR:
{
regOAMADDR = value;
break;
}
case Register::OAMDATA:
{
oam[regOAMADDR] = value;
++regOAMADDR;
break;
}
case Register::PPUSCROLL:
{
if (firstWrite)
{
// yyy NNYY YYYX XXXX
// t: --- ---- ---H GFED = d: HGFE D---
// x: CBA = d: ---- -CBA
// w: = 1
tempAddress.scrollCoarseX = (value & 0xF8u) >> 3u;
scrollFineX = value & 0x7u;
firstWrite = false;
}
else
{
// yyy NNYY YYYX XXXX
// t: CBA --HG FED- ---- = d: HGFE DCBA
// w: = 0
tempAddress.scrollCoarseY = (value & 0xF8u) >> 3u;
tempAddress.scrollFineY = value & 0x7u;
firstWrite = true;
}
break;
}
case Register::PPUADDR:
{
// MSB
if (firstWrite)
{
// yyy NNYY YYYX XXXX
// t: -FE DCBA ---- ---- = d: --FE DCBA
// t: X-- ---- ---- ---- = 0
// w: = 1
tempAddress.scrollCoarseY &= ~(0x18u);
tempAddress.scrollCoarseY |= (value & 0x3u) << 3u;
tempAddress.nametableY = (value & 0x8u) >> 3u;
tempAddress.nametableX = (value & 0x4u) >> 2u;
tempAddress.scrollFineY = (value & 0x30u) >> 4u;
tempAddress.scrollFineY &= ~(0x4u);
firstWrite = false;
}
// LSB
else
{
// yyy NNYY YYYX XXXX
// t: ... .... HGFE DCBA = d: HGFE DCBA
// v = t
// w: = 0
tempAddress.scrollCoarseY &= ~(0x7u);
tempAddress.scrollCoarseY |= (value & 0xE0u) >> 5u;
tempAddress.scrollCoarseX = value & 0x1Fu;
currentAddress = tempAddress;
firstWrite = true;
}
break;
}
case Register::PPUDATA:
{
WriteMemory(currentAddress.GetValue(), value);
uint16_t temp = currentAddress.GetValue();
temp += (regPPUCTRL.vramAddrIncrement) ? 32u : 1u;
currentAddress.SetValue(temp);
break;
}
default: break;
}
}
uint8_t PPU::ReadRegister(Register reg)
{
uint8_t byte{};
switch (reg)
{
case Register::PPUSTATUS:
{
byte = regPPUSTATUS.GetByte();
regPPUSTATUS.vblankStarted = 0u;
firstWrite = true;
break;
}
case Register::OAMDATA:
{
byte = oam[regOAMADDR];
break;
}
case Register::PPUDATA:
{
// Returned byte is buffered from last read of PPUDATA
byte = oldByte;
oldByte = ReadMemory(currentAddress.GetValue());
// If reading palette data, return actual byte instead of buffered byte
if (currentAddress.GetValue() >= BG_PALETTE_START_ADDRESS)
{
byte = oldByte;
}
uint16_t temp = currentAddress.GetValue();
temp += (regPPUCTRL.vramAddrIncrement) ? 32u : 1u;
currentAddress.SetValue(temp);
break;
}
default: break;
}
return byte;
}
void PPU::WriteMemory(uint16_t address, uint8_t value)
{
nes->Write(BusSource::PPU, address, value);
}
uint8_t PPU::ReadMemory(uint16_t address)
{
return nes->Read(BusSource::PPU, address);
}
void PPU::FetchNT()
{
if (!regPPUMASK.showBackground)
{return;}
uint16_t address = 0x2000u | (currentAddress.scrollCoarseY << 5u) | currentAddress.scrollCoarseX;
nametableLatch = ReadMemory(address);
}
void PPU::FetchAT()
{
if (!regPPUMASK.showBackground)
{return;}
// Bits 4,3,2 of Coarse Y Scroll are Bits 5,4,3 of attribute table address
// Bits 4,3,2 of Coarse X Scroll are Bits 2,1,0 of attribute table address
uint16_t address = ATTRIBUTE_TABLE_START
| ((currentAddress.scrollCoarseY & 0x1Cu) << 1u)
| ((currentAddress.scrollCoarseX & 0x1Cu) >> 2u);
// Bit 1 of Coarse Y Scroll is Block Row (0 or 1)
// Bit 1 of Coarse X Scroll is Block Col (0 or 1)
// Y determines if top or bottom
// X determines if left or right
uint8_t at = ReadMemory(address);
uint8_t location = ((currentAddress.scrollCoarseY & 0x2u))
| ((currentAddress.scrollCoarseX & 0x2u) >> 1u);
switch (location)
{
// Top Left
case 0:
{
attributeTableLatch = at & 0x03u;
break;
}
// Top Right
case 1:
{
attributeTableLatch = (at & 0x0Cu) >> 2u;
break;
}
// Bottom Left
case 2:
{
attributeTableLatch = (at & 0x30u) >> 4u;
break;
}
// Bottom Right
case 3:
{
attributeTableLatch = (at & 0xC0u) >> 6u;
break;
}
default: break;
}
}
void PPU::FetchPTLow()
{
if (!regPPUMASK.showBackground)
{return;}
uint16_t address = regPPUCTRL.bgPatternTableAddr ? PATTERN_TABLE_1_START : PATTERN_TABLE_0_START;
address += (nametableLatch * 16u) + currentAddress.scrollFineY;
patternTableLowLatch = ReadMemory(address);
}
void PPU::FetchPTHigh()
{
if (!regPPUMASK.showBackground)
{return;}
uint16_t address = regPPUCTRL.bgPatternTableAddr ? PATTERN_TABLE_1_START : PATTERN_TABLE_0_START;
address += (nametableLatch * 16u) + 8u + currentAddress.scrollFineY;
patternTableHighLatch = ReadMemory(address);
}
void PPU::SetVBlank()
{
regPPUSTATUS.vblankStarted = 1u;
if (regPPUCTRL.nmiEnable)
{
nes->nmi = true;
}
}
void PPU::SetTileX()
{
if (!regPPUMASK.showBackground)
{return;}
// yyy NNYY YYYX XXXX
// v: --- -F-- ---E DCBA = t: --- -F-- ---E DCBA
currentAddress.nametableX = tempAddress.nametableX;
currentAddress.scrollCoarseX = tempAddress.scrollCoarseX;
}
void PPU::SetTileY()
{
if (!regPPUMASK.showBackground)
{return;}
// yyy NNYY YYYX XXXX
// v: IHG F-ED CBA- ---- = t: IHG F-ED CBA- ----
currentAddress.scrollCoarseY = tempAddress.scrollCoarseY;
currentAddress.nametableY = tempAddress.nametableY;
currentAddress.scrollFineY = tempAddress.scrollFineY;
}
void PPU::Draw()
{
if (!regPPUMASK.showBackground)
{return;}
// Draw occurs on cycle 2
uint8_t x = currentCycle - 2;
uint8_t h = (patternTableHighShift & 0x8000u) >> (15u - scrollFineX);
uint8_t l = (patternTableLowShift & 0x8000u) >> (15u - scrollFineX);
uint8_t bgColor = (h << 1u) | l;
uint8_t paletteIndexHigh = (atShiftHigh & 0x80u) >> (7u - scrollFineX);
uint8_t paletteIndexLow = (atShiftLow & 0x80u) >> (7u - scrollFineX);
uint8_t pIndex = (paletteIndexHigh << 1u) | paletteIndexLow;
uint8_t paletteIndex = palette[pIndex][bgColor];
uint32_t color = nes->palette[paletteIndex].GetValue();
video[currentScanline * VIDEO_WIDTH + x] = color;
}
void PPU::LoadBackground()
{
if (!regPPUMASK.showBackground)
{return;}
patternTableHighShift &= ~(0xFFu);
patternTableHighShift |= (patternTableHighLatch);
patternTableLowShift &= ~(0xFFu);
patternTableLowShift |= (patternTableLowLatch);
attribute = attributeTableLatch;
}
void PPU::IncrementTileX()
{
if (!regPPUMASK.showBackground)
{return;}
// Increment coarse X scroll and wrap if needed
if (currentAddress.scrollCoarseX == 31)
{
currentAddress.scrollCoarseX = 0;
currentAddress.nametableX = currentAddress.nametableX ? 0u : 1u;
}
else
{
++currentAddress.scrollCoarseX;
}
}
void PPU::IncrementTileY()
{
if (!regPPUMASK.showBackground)
{return;}
// Increment Y scroll and wrap if needed
if (currentAddress.scrollFineY < 7)
{
++currentAddress.scrollFineY;
}
else
{
currentAddress.scrollFineY = 0;
if (currentAddress.scrollCoarseY == 29)
{
currentAddress.scrollCoarseY = 0;
currentAddress.nametableY = currentAddress.nametableY ? 0u : 1u;
}
else if (currentAddress.scrollCoarseY == 31)
{
currentAddress.scrollCoarseY = 0;
}
else
{
++currentAddress.scrollCoarseY;
}
}
}
void PPU::ClearFlags()
{
regPPUSTATUS.vblankStarted = 0u;
regPPUSTATUS.spriteOverflow = 0u;
regPPUSTATUS.sprite0Hit = 0u;
}
void PPU::ShiftBG()
{
if (!regPPUMASK.showBackground)
{return;}
patternTableHighShift <<= 1u;
patternTableLowShift <<= 1u;
atShiftLow <<= 1u;
atShiftHigh <<= 1u;
atShiftLow |= attribute & 0x1u;
atShiftHigh |= (attribute & 0x2u) >> 1u;
}
uint8_t PPU::PpuStatus::GetByte()
{
uint8_t byte = vblankStarted << 7u | sprite0Hit << 6u | spriteOverflow << 5u | previousLsb;
return byte;
}
void PPU::PpuMask::SetByte(uint8_t byte)
{
blueEmphasis = (byte & 0x80u) >> 7u;
greenEmphasis = (byte & 0x40u) >> 6u;
redEmphasis = (byte & 0x20u) >> 5u;
showSprites = (byte & 0x10u) >> 4u;
showBackground = (byte & 0x08u) >> 3u;
showSpritesLeft = (byte & 0x04u) >> 2u;
showBackgroundLeft = (byte & 0x02u) >> 1u;
grayscale = byte & 0x01u;
}
void PPU::PpuCtrl::SetByte(uint8_t byte)
{
nmiEnable = (byte & 0x80u) >> 7u;
masterSlaveSelect = (byte & 0x40u) >> 6u;
spriteSize = (byte & 0x20u) >> 5u;
bgPatternTableAddr = (byte & 0x10u) >> 4u;
spritePatternTableAddr = (byte & 0x08u) >> 3u;
vramAddrIncrement = (byte & 0x04u) >> 2u;
nametableBaseAddr = ((byte & 0x02u) >> 1u | (byte & 0x01u));
}
void PPU::Address::SetValue(uint16_t value)
{
// yyy NNYY YYYX XXXX
scrollFineY = (value & 0x7000u) >> 12u;
nametableX = (value & 0x0800u) >> 11u;
nametableY = (value & 0x0400u) >> 10u;
scrollCoarseY = (value & 0x03E0u) >> 5u;
scrollCoarseX = value & 0x0001Fu;
}
uint16_t PPU::Address::GetValue()
{
// yyy NNYY YYYX XXXX
return (scrollFineY << 12u) | (nametableY << 11u) | (nametableX << 10u) | (scrollCoarseY << 5u) | scrollCoarseX;
}

164
Source/PPU/PPU.hpp
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@ -1,164 +0,0 @@
#pragma once
#include <cstdint>
#include <queue>
class NES;
const unsigned int VRAM_SIZE = 2048u;
const unsigned int PALETTE_SIZE = 8u;
const unsigned int OAM_SIZE = 256u;
const unsigned int VIDEO_WIDTH = 256u;
const unsigned int VIDEO_HEIGHT = 240u;
const unsigned int TOTAL_SCANLINES = 262u;
const unsigned int TOTAL_DOTS = 341u;
class PPU
{
public:
PPU();
enum Register
{
PPUCTRL = 0x00,
PPUMASK = 0x01,
PPUSTATUS = 0x02,
OAMADDR = 0x03,
OAMDATA = 0x04,
PPUSCROLL = 0x05,
PPUADDR = 0x06,
PPUDATA = 0x07,
};
void Tick();
void WriteRegister(Register reg, uint8_t value);
uint8_t ReadRegister(Register reg);
void WriteMemory(uint16_t address, uint8_t value);
uint8_t ReadMemory(uint16_t address);
private:
friend class NES;
void FetchNT();
void FetchAT();
void FetchPTLow();
void FetchPTHigh();
void SetVBlank();
void SetTileX();
void SetTileY();
void LoadBackground();
void Draw();
void IncrementTileX();
void IncrementTileY();
void ClearFlags();
enum Event
{
FETCH_NT = 0x1,
FETCH_AT = 0x2,
FETCH_PT_LOW = 0x4,
FETCH_PT_HIGH = 0x8,
LOAD_BACKGROUND = 0x10,
SHIFT_BACKGROUND = 0x20,
SET_VBLANK = 0x40,
SET_TILE_X = 0x80,
SET_TILE_Y = 0x100,
DRAW = 0x200,
INCREMENT_TILE_X = 0x400,
INCREMENT_TILE_Y = 0x800,
CLEAR_FLAGS = 0x1000
};
struct PpuCtrl
{
void SetByte(uint8_t byte);
uint16_t nametableBaseAddr;
uint8_t vramAddrIncrement;
uint8_t spritePatternTableAddr;
uint8_t bgPatternTableAddr;
uint8_t spriteSize;
uint8_t masterSlaveSelect;
uint8_t nmiEnable;
};
struct PpuMask
{
void SetByte(uint8_t byte);
uint8_t grayscale;
uint8_t showBackgroundLeft;
uint8_t showSpritesLeft;
uint8_t showBackground;
uint8_t showSprites;
uint8_t redEmphasis;
uint8_t greenEmphasis;
uint8_t blueEmphasis;
};
struct PpuStatus
{
uint8_t GetByte();
uint8_t vblankStarted;
uint8_t sprite0Hit;
uint8_t spriteOverflow;
uint8_t previousLsb;
};
struct Address
{
uint16_t GetValue();
void SetValue(uint16_t value);
uint8_t scrollFineY;
uint8_t nametableX;
uint8_t nametableY;
uint8_t scrollCoarseX;
uint8_t scrollCoarseY;
};
// External Registersgg
PpuCtrl regPPUCTRL{}; // $2000, W
PpuMask regPPUMASK{}; // $2001, W
PpuStatus regPPUSTATUS{}; // $2002, R
uint8_t regOAMADDR{}; // $2003, W
uint8_t oldByte{};
// Internal Registers
Address currentAddress{};
Address tempAddress{};
uint8_t scrollFineX{};
bool firstWrite{true};
// Timing tracking
uint32_t events[TOTAL_SCANLINES][TOTAL_DOTS]{};
uint16_t currentCycle{};
uint16_t currentScanline{};
// Memory
uint8_t ram[VRAM_SIZE]{};
uint8_t palette[PALETTE_SIZE][4]{};
uint8_t oam[OAM_SIZE]{};
uint32_t video[VIDEO_WIDTH * VIDEO_HEIGHT]{};
uint64_t frameNumber{};
// Shift registers and latches
uint16_t patternTableHighShift{};
uint16_t patternTableLowShift{};
uint8_t atShiftLow{};
uint8_t atShiftHigh{};
uint8_t nametableLatch{};
uint8_t attributeTableLatch{};
uint8_t attribute;
uint8_t patternTableLowLatch{};
uint8_t patternTableHighLatch{};
NES* nes;
void ShiftBG();
};

157
Source/Platform.cpp
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@ -1,157 +0,0 @@
#include "Platform.hpp"
#include "Input.hpp"
#include <SDL2/SDL.h>
Platform::Platform(char const* title, int windowWidth, int windowHeight, int textureWidth, int textureHeight)
{
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow(title, 0, 0, windowWidth, windowHeight, SDL_WINDOW_SHOWN);
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
texture = SDL_CreateTexture(
renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, textureWidth, textureHeight);
}
Platform::~Platform()
{
SDL_DestroyTexture(texture);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
}
void Platform::Update(void const* buffer, int pitch)
{
SDL_UpdateTexture(texture, nullptr, buffer, pitch);
SDL_RenderClear(renderer);
SDL_RenderCopy(renderer, texture, nullptr, nullptr);
SDL_RenderPresent(renderer);
}
bool Platform::ProcessInput(uint8_t* buttons)
{
bool quit = false;
SDL_Event event{};
while (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
{
quit = true;
break;
}
case SDL_KEYDOWN:
{
switch (event.key.keysym.sym)
{
case SDLK_ESCAPE:
{
quit = true;
break;
}
case SDLK_UP:
{
{buttons[Buttons::Up] = 1u;}
break;
}
case SDLK_DOWN:
{
{buttons[Buttons::Down] = 1u;}
break;
}
case SDLK_LEFT:
{
{buttons[Buttons::Left] = 1u;}
break;
}
case SDLK_RIGHT:
{
{buttons[Buttons::Right] = 1u;}
break;
}
case SDLK_LSHIFT:
{
buttons[Buttons::Select] = 1u;
break;
}
case SDLK_RETURN:
{
{buttons[Buttons::Start] = 1u;}
break;
}
case SDLK_z:
{
{buttons[Buttons::A] = 1u;}
break;
}
case SDLK_x:
{
{buttons[Buttons::B] = 1u;}
break;
}
}
break;
}
case SDL_KEYUP:
{
switch (event.key.keysym.sym)
{
case SDLK_UP:
{
{buttons[Buttons::Up] = 0u;}
break;
}
case SDLK_DOWN:
{
{buttons[Buttons::Down] = 0u;}
break;
}
case SDLK_LEFT:
{
{buttons[Buttons::Left] = 0u;}
break;
}
case SDLK_RIGHT:
{
{buttons[Buttons::Right] = 0u;}
break;
}
case SDLK_LSHIFT:
{
{buttons[Buttons::Select] = 0u;}
break;
}
case SDLK_RETURN:
{
{buttons[Buttons::Start] = 0u;}
break;
}
case SDLK_z:
{
{buttons[Buttons::A] = 0u;}
break;
}
case SDLK_x:
{
{buttons[Buttons::B] = 0u;}
break;
}
}
break;
}
}
}
return quit;
}

23
Source/Platform.hpp
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@ -1,23 +0,0 @@
#pragma once
#include <cstdint>
#include "Input.hpp"
class SDL_Window;
class SDL_Renderer;
class SDL_Texture;
class Platform
{
public:
Platform(char const* title, int windowWidth, int windowHeight, int textureWidth, int textureHeight);
~Platform();
void Update(void const* buffer, int pitch);
bool ProcessInput(uint8_t* buttons);
SDL_Window* window{};
SDL_Renderer* renderer{};
SDL_Texture* texture{};
};