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MMC1 mapper

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This commit is contained in:
Selim Mustafaev 2025-08-06 13:23:17 +03:00
parent c0ac8bfb58
commit f114104e8e
12 changed files with 237 additions and 24 deletions
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3
CMakeLists.txt
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@ -32,7 +32,8 @@ add_executable(nes
src/Mapper/Mapper1.cpp
src/Mapper/Mapper1.h
src/Bus.cpp
src/Bus.h)
src/Bus.h
src/Utils.h)
find_package(SDL2 CONFIG REQUIRED)
find_package(fmt REQUIRED)

4
examples/sdl/main.cpp
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@ -11,7 +11,7 @@ int main() {
nes::System device;
nes::SdlWindow window(nes::Ppu::SCREEN_WIDTH, nes::Ppu::SCREEN_HEIGHT);
window.setSize(nes::Ppu::SCREEN_WIDTH, nes::Ppu::SCREEN_HEIGHT);
window.setSize(nes::Ppu::SCREEN_WIDTH*2, nes::Ppu::SCREEN_HEIGHT*2);
SDL_Event e;
bool frameRendered = false;
@ -22,7 +22,7 @@ int main() {
});
device.connect(std::make_shared<SdlKeyboardController>());
//device.insertCartridge("/home/selim/Downloads/dk.nes");
device.insertCartridge("/Users/selim/Documents/smb.nes");
device.insertCartridge("/Users/selim/Documents/drm.nes");
//device.insertCartridge("C:\\Users\\selim\\Documents\\nestest.nes");
auto frameStart = std::chrono::steady_clock::now();

25
src/Bus.cpp
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@ -5,6 +5,8 @@
#include "Bus.h"
#include <iostream>
#include "../../../../../../opt/homebrew/Cellar/fmt/11.2.0/include/fmt/format.h"
namespace nes {
Bus::Bus(uint8_t *ram,
@ -53,12 +55,6 @@ namespace nes {
else if(address >= 0x2000 && address < 0x4000) {
return _ppu->read(address & 0x0007);
}
else if (address >= 0x6000 && address < 0x8000) {
return _cartridge->readRam(address);
}
else if(address >= 0x8000) {
return _cartridge->readPrg(address);
}
else if(address == 0x4016) {
return _controller1->read();
}
@ -67,6 +63,12 @@ namespace nes {
return _controller2->read();
}
}
else if (address >= 0x6000 && address < 0x8000) {
return _cartridge->readRam(address);
}
else if(address >= 0x8000) {
return _cartridge->readPrg(address);
}
return 0;
}
@ -78,9 +80,6 @@ namespace nes {
else if(address >= 0x2000 && address < 0x4000) {
_ppu->write(address & 0x0007, value);
}
else if(address >= 0x8000) {
std::cout << "Cartridge (PRG) write at address: " << address << std::endl;
}
else if(address == 0x4014) {
_dma->start(value);
}
@ -92,6 +91,14 @@ namespace nes {
_controller2->poll();
}
}
else if (address >= 0x6000 && address < 0x8000) {
_cartridge->writeRam(address, value);
}
else if(address >= 0x8000) {
_cartridge->writePrg(address, value);
} else {
//fmt::println("unknown bus write at address: {:#06x}, value: {}", address, value);
}
}
}

32
src/Cartridge.cpp
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@ -19,9 +19,6 @@ namespace nes {
std::ifstream rom(path, std::ios::binary);
rom.read(reinterpret_cast<char*>(_romData.get()), static_cast<std::streamsize>(romSize));
// UB here
// Should be std::start_lifetime_as<RomHeader>(_romData);
// when it become available
_header = reinterpret_cast<RomHeader*>(_romData.get());
if (memcmp(_header->magic, ROM_MAGIC, sizeof(ROM_MAGIC)) != 0) {
@ -32,15 +29,25 @@ namespace nes {
const size_t chrSize = _header->chrChunks*CHR_CHUNK_SIZE;
_prgRom = std::span(_romData.get() + sizeof(RomHeader), prgSize);
_chrRom = std::span(_romData.get() + sizeof(RomHeader) + prgSize, chrSize);
switch (_header->flags.mapper) {
if (chrSize == 0) {
_chrRam = std::make_unique<uint8_t[]>(CHR_CHUNK_SIZE);
_chrRom = std::span(_chrRam.get(), CHR_CHUNK_SIZE);
} else {
_chrRom = std::span(_romData.get() + sizeof(RomHeader) + prgSize, chrSize);
}
uint8_t mapper = _header->flags.mapper | (_header->flags2.upperMapper << 4);
switch (mapper) {
case 0:
_mapper = std::make_unique<Mapper0>(_header->prgChunks, _header->chrChunks);
break;
case 1:
_mapper = std::make_unique<Mapper1>(_header->prgChunks, _header->chrChunks);
break;
default:
_mapper = std::make_unique<Mapper0>(_header->prgChunks, _header->chrChunks);
throw std::runtime_error("unknown mapper");
}
if (const auto ramSize = _mapper->ramSize(); ramSize > 0) {
@ -53,16 +60,29 @@ namespace nes {
return _prgRom[mappedAddress];
}
void Cartridge::writePrg(uint16_t address, uint8_t value) {
_mapper->write(address, value);
}
uint8_t Cartridge::readChr(uint16_t address) {
uint32_t mappedAddress = _mapper->mapChr(address);
return _chrRom[mappedAddress];
}
void Cartridge::writeChr(uint16_t address, uint8_t value) {
_chrRom[address] = value;
}
uint8_t Cartridge::readRam(uint16_t address) {
uint32_t mappedAddress = _mapper->mapRam(address);
return _ram[mappedAddress];
}
void Cartridge::writeRam(uint16_t address, uint8_t value) {
uint32_t mappedAddress = _mapper->mapRam(address);
_ram[mappedAddress] = value;
}
Cartridge::Mirroring Cartridge::mirroring() const {
return _header->flags.mirroring;
}

14
src/Cartridge.h
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@ -34,12 +34,20 @@ namespace nes {
uint8_t mapper: 4;
};
struct Flags2 {
uint8_t reserved: 2;
uint8_t version: 2;
uint8_t upperMapper: 4;
};
struct RomHeader {
uint8_t magic[4];
uint8_t prgChunks;
uint8_t chrChunks;
Flags flags;
uint8_t reserved[9];
Flags2 flags2;
uint8_t prgRamSize;
uint8_t reserved[7];
};
public:
@ -47,8 +55,11 @@ namespace nes {
public:
uint8_t readPrg(uint16_t address);
void writePrg(uint16_t address, uint8_t value);
uint8_t readChr(uint16_t address);
void writeChr(uint16_t address, uint8_t value);
uint8_t readRam(uint16_t address);
void writeRam(uint16_t address, uint8_t value);
Mirroring mirroring() const;
private:
@ -58,6 +69,7 @@ namespace nes {
std::span<uint8_t> _prgRom;
std::span<uint8_t> _chrRom;
std::unique_ptr<uint8_t[]> _ram;
std::unique_ptr<uint8_t[]> _chrRam;
};
}

1
src/Mapper/Mapper.h
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@ -20,6 +20,7 @@ namespace nes {
virtual uint32_t mapChr(uint16_t address) = 0;
virtual uint32_t mapRam(uint16_t address) = 0;
virtual size_t ramSize() = 0;
virtual void write(uint16_t address, uint8_t value) = 0;
protected:
uint8_t _prgBanks;

4
src/Mapper/Mapper0.cpp
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@ -21,4 +21,8 @@ namespace nes {
size_t Mapper0::ramSize() {
return 0;
}
void Mapper0::write(uint16_t address, uint8_t value) {
// not used
}
}

1
src/Mapper/Mapper0.h
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@ -19,6 +19,7 @@ namespace nes {
uint32_t mapChr(uint16_t address) override;
uint32_t mapRam(uint16_t address) override;
size_t ramSize() override;
void write(uint16_t address, uint8_t value) override;
};
}

87
src/Mapper/Mapper1.cpp
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@ -2,25 +2,52 @@
// Created by Selim Mustafaev on 27.06.2025.
//
#include "../Utils.h"
#include "Mapper1.h"
namespace nes {
Mapper1::Mapper1(uint8_t prgBanks, uint8_t chrBanks): Mapper(prgBanks, chrBanks) {
_controlReg.prgBankMode = FixLast16;
_controlReg.chrBankMode = Double4;
_prgBank16Hi = _prgBanks - 1;
}
uint32_t Mapper1::mapPrg(uint16_t address) {
if(_controlReg.prgBankMode == FixFirst16 || _controlReg.prgBankMode == FixLast16) {
if (address >= PRG_FIRST_BANK && address < PRG_SECOND_BANK) {
return _prgBank16Lo*PRG_BANK16_SIZE + clampBits<14>(address);
} else if (address >= PRG_SECOND_BANK && address < PRG_END) {
return _prgBank16Hi*PRG_BANK16_SIZE + clampBits<14>(address);
}
} else {
return _prgBank32*PRG_BANK32_SIZE + clampBits<15>(address);
}
return address;
}
uint32_t Mapper1::mapChr(uint16_t address) {
if (_chrBanks == 0) {
return address;
}
switch (_controlReg.chrBankMode) {
case Single8:
return _chrBank8*CHR_BANK8_SIZE + clampBits<13>(address);
case Double4:
if (address >= CHR_FIRST_BANK && address < CHR_SECOND_BANK) {
return _chrBank4Lo*CHR_BANK4_SIZE + clampBits<12>(address);
} else if (address < CHR_END) {
return _chrBank4Hi*CHR_BANK4_SIZE + clampBits<12>(address);
}
default:
return address;
}
}
uint32_t Mapper1::mapRam(uint16_t address) {
return address & 0x1FFF;
}
@ -28,4 +55,60 @@ namespace nes {
size_t Mapper1::ramSize() {
return 32*1024;
}
void Mapper1::write(uint16_t address, uint8_t value) {
// Reset shift register
if (bitIsSet<7>(value)) {
_shiftReg = 0;
_controlReg.prgBankMode = FixLast16;
_prgBank16Hi = _prgBanks - 1;
_writes = 0;
return;
}
_writes++;
_shiftReg = (_shiftReg >> 1) | ((value & 0x1) << 4);
if (_writes == 5) {
auto command = static_cast<Command>(getBits<13,2>(address));
switch (command) {
case SetControlRegister:
_controlReg.value = clampBits<5>(_shiftReg);
break;
case SetChrBankLo:
if (_controlReg.chrBankMode == Double4) {
_chrBank4Lo = clampBits<5>(_shiftReg);
} else {
_chrBank8 = maskBits<1,4>(_shiftReg);
}
break;
case SetChrBankHi:
if (_controlReg.chrBankMode == Double4) {
_chrBank4Hi = clampBits<5>(_shiftReg);
}
break;
case ConfigurePrgBanks:
switch (_controlReg.prgBankMode) {
case FixFirst32:
case FixLast32:
_prgBank32 = getBits<1,3>(_shiftReg);
break;
case FixFirst16:
_prgBank16Lo = 0;
_prgBank16Hi = clampBits<4>(_shiftReg);
break;
case FixLast16:
_prgBank16Lo = clampBits<4>(_shiftReg);
_prgBank16Hi = _prgBanks - 1;
break;
}
break;
}
_writes = 0;
_shiftReg = 0;
}
}
}

39
src/Mapper/Mapper1.h
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@ -11,6 +11,19 @@ namespace nes {
class Mapper1 final : public Mapper {
public:
const uint16_t PRG_FIRST_BANK = 0x8000;
const uint16_t PRG_SECOND_BANK = 0xBFFF;
const uint16_t PRG_END = 0xFFFF;
const uint16_t CHR_FIRST_BANK = 0x0000;
const uint16_t CHR_SECOND_BANK = 0x0FFF;
const uint16_t CHR_END = 0x1FFF;
const size_t PRG_BANK16_SIZE = 16*1024;
const size_t PRG_BANK32_SIZE = 32*1024;
const size_t CHR_BANK4_SIZE = 4*1024;
const size_t CHR_BANK8_SIZE = 8*1024;
enum PrgBankMode: uint8_t {
FixFirst32 = 0,
FixLast32 = 1,
@ -23,9 +36,23 @@ namespace nes {
Double4 = 1
};
enum Command: uint8_t {
SetControlRegister = 0,
SetChrBankLo = 1,
SetChrBankHi = 2,
ConfigurePrgBanks = 3
};
enum Mirroring: uint8_t {
OneScreenLowerBank = 0,
OneScreenUpperBank = 1,
Vertical = 2,
Horizontal = 3
};
union ControlRegister {
struct {
uint8_t reserved: 2;
Mirroring mirroring: 2;
PrgBankMode prgBankMode: 2;
ChrBankMode chrBankMode: 1;
};
@ -34,6 +61,7 @@ namespace nes {
public:
using Mapper::Mapper;
Mapper1(uint8_t prgBanks, uint8_t chrBanks);
~Mapper1() override = default;
public:
@ -41,11 +69,20 @@ namespace nes {
uint32_t mapChr(uint16_t address) override;
uint32_t mapRam(uint16_t address) override;
size_t ramSize() override;
void write(uint16_t address, uint8_t value) override;
private:
ControlRegister _controlReg = {};
uint8_t _shiftReg = 0;
uint8_t _writes = 0;
uint8_t _chrBank4Lo = 0;
uint8_t _chrBank4Hi = 0;
uint8_t _chrBank8 = 0;
uint8_t _prgBank16Lo = 0;
uint8_t _prgBank16Hi = 0;
uint8_t _prgBank32 = 0;
};
}

3
src/Ppu.cpp
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@ -4,6 +4,8 @@
#include "Ppu.h"
#include "../../../../../../opt/homebrew/Cellar/fmt/11.2.0/include/fmt/base.h"
#ifdef NES_LOGGING
#include <fmt/format.h>
#endif
@ -228,6 +230,7 @@ namespace nes {
_oam->write(value);
break;
default:
fmt::println("unknown ppu write");
break;
}
}

44
src/Utils.h Normal file
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@ -0,0 +1,44 @@
//
// Created by Selim Mustafaev on 02.07.2025.
//
#ifndef UTILS_H
#define UTILS_H
#include <concepts>
namespace nes {
template<size_t pos, size_t len, std::integral T>
consteval T createBitMask() {
T hi = (1 << (pos + len)) - 1;
T lo = (1 << pos) - 1;
return hi - lo;
}
template<size_t N, std::integral T>
bool bitIsSet(T value) {
return value & (1 << N);
}
template<size_t pos, size_t len, std::integral T>
T getBits(T value) {
static_assert(sizeof(T)*8 >= (pos + len - 1));
return (value >> pos) & ((1 << len) - 1);
}
template<size_t pos, size_t len, std::integral T>
T maskBits(T value) {
static_assert(sizeof(T)*8 >= (pos + len - 1));
return value & createBitMask<pos, len, T>();
}
template<size_t N, std::integral T>
T clampBits(T value) {
static_assert(sizeof(T)*8 >= N);
return value & ((1 << N) - 1);
}
}
#endif //UTILS_H