first tests now pass

2024-04-02 17:38:43 -07:00
parent 0f95c0da86
commit 5c573789c9
12 changed files with 557 additions and 230 deletions
--- a/src/addressSpace.cpp
+++ b/src/addressSpace.cpp
@@ -42,6 +42,6 @@ void AddressSpace::loadGame(const std::string& filename) {
 	            std::istream_iterator<Byte>(rom),
 	            std::istream_iterator<Byte>());

-	memcpy(memoryLayout.romBank0, game.data(), ROM_BANK_SIZE);
-	memcpy(memoryLayout.romBankSwitch, game.data() + ROM_BANK_SIZE, ROM_BANK_SIZE);
+	memoryLayout.romBank0 = game.data();
+	memoryLayout.romBankSwitch = game.data() + ROM_BANK_SIZE;
 }
--- a/src/addressSpace.hpp
+++ b/src/addressSpace.hpp
@@ -12,34 +12,76 @@
 class AddressSpace {
 	bool bootromLoaded = true;
 	Byte bootrom[BOOTROM_SIZE] = {0};
-
-public:
 	std::vector<Byte> game;

+public:
 	AddressSpace() {
 		// Initialize the memory to zero
 		memoryLayout = {};
-		std::memset(memoryLayout.memory, 0, sizeof(memoryLayout.memory));
 	}

-	// Nested union for the memory layout
-	union MemoryLayout {
-		Byte memory[0x10000];
+	Byte* cartridgeRam = nullptr;

-		struct {
-			Byte romBank0[ROM_BANK_SIZE]; // Mapped to 0x0000
-			Byte romBankSwitch[ROM_BANK_SIZE]; // Mapped to 0x4000
-			Byte vram[0x2000]; // Mapped to 0x8000
-			Byte externalRam[0x2000]; // Mapped to 0xA000
-			Byte memoryBank1[0x1000]; // Mapped to 0xC000
-			Byte memoryBank2[0x1000]; // Mapped to 0xD000
-			Byte echoRam[0x1E00]; // Mapped to 0xE000 (Echo RAM, mirrors 0xC000 to 0xDFFF)
-			Byte spriteAttributeTable[0xA0]; // Mapped to 0xFE00
-			Byte notUsable[0x60]; // Mapped to 0xFEA0
-			Byte io[0x80]; // Mapped to 0xFF00, 0xFF0F is interrupt flag
-			Byte specialRam[0x7F]; // Mapped to 0xFF80
-			Byte interuptEnableReg; // Mapped to 0xFFFF
-		};
+	struct {
+		Byte* romBank0; //[ROM_BANK_SIZE] Mapped to 0x0000
+		Byte* romBankSwitch; //[ROM_BANK_SIZE] Mapped to 0x4000
+		Byte vram[0x2000]; //Mapped to 0x8000
+		Byte* externalRam; //[0x2000]; Mapped to 0xA000
+		Byte memoryBank1[0x1000]; //Mapped to 0xC000
+		Byte memoryBank2[0x1000]; //Mapped to 0xD000
+		Byte oam[0xA0]; //Mapped to 0xFE00
+		Byte notUsable[0x60]; //Mapped to 0xFEA0
+		//General purpose hardware registers
+		Byte JOYP;
+		Byte SB;
+		Byte SC;
+		Byte DIV;
+		//Timer registers
+		Byte TIMA;
+		Byte TMA;
+		Byte TAC;
+		//interrupt flag and enable
+		Byte IF;
+		//Sound registers
+		Byte NR10;
+		Byte NR11;
+		Byte NR12;
+		Byte NR13;
+		Byte NR14;
+		Byte NR20; //not used
+		Byte NR21;
+		Byte NR22;
+		Byte NR23;
+		Byte NR24;
+		Byte NR30;
+		Byte NR31;
+		Byte NR32;
+		Byte NR33;
+		Byte NR34;
+		Byte NR40; //unused
+		Byte NR41;
+		Byte NR42;
+		Byte NR43;
+		Byte NR44;
+		Byte NR50;
+		Byte NR51;
+		Byte NR52;
+		Byte waveRam[0x10];
+		//PPU registers
+		Byte LCDC;
+		Byte STAT;
+		Byte SCY;
+		Byte SCX;
+		Byte LY;
+		Byte LYC;
+		Byte DMA;
+		Byte BGP;
+		Byte OBP0;
+		Byte OBP1;
+		Byte WY;
+		Byte WX;
+		Byte specialRam[0x7F]; //Mapped to 0xFF80
+		Byte IE; // Mapped to 0xFFFF
 	} memoryLayout{};

 	void unmapBootrom();
@@ -49,35 +91,281 @@ public:
 	void loadGame(const std::string& filename);

 	void determineMBCInfo();
+	static bool testMBCWrite(Word address);
+	Byte* MBCRead(Word address);
+	//prevents seg faults when programs with no MBC try to write to ROM
+	Byte dummyVal = 0;
+	void MBCUpdate();
+	void loadRomBank();
+	void createRamBank();
+	void loadRamBank();
 	MBCType MBC = {};
 	uint32_t romSize = 0;
 	uint32_t romBanks = 0;
 	uint32_t externalRamSize = 0;
 	uint32_t externalRamBanks = 0;
-	Byte romBankRegister = 0x01;
-	Byte ramBankRegister = 0x00;
+
+	//Selected ROM Bank = (Secondary Bank << 5) + ROM Bank
+	Byte selectedRomBank = 0;
+	Byte romBankRegister = 0x00;
+	//2 bit register acts as secondary rom bank register or ram bank number
+	Byte twoBitBankRegister = 0x0;
+	Byte selectedExternalRamBank = 0;
 	Byte romRamSelect = 0x00;
+	Byte ramEnable = 0x00;
 	//MBC3
 	Byte latchClockData = 0x00;
 	Byte ramBankRTCRegister = 0x00;

-	//overload [] for echo ram and bootrom support
-	Byte operator[](const uint32_t address) const {
-		if (address >= 0xE000 && address < 0xFE00)
-			return memoryLayout.echoRam[address - 0x2000];
+	//read
+	Byte operator[](const Word address) const {
 		if (address < 0x0100 && bootromLoaded)
 			return bootrom[address];
+		if (address < 0x4000)
+			return memoryLayout.romBank0[address];
+		if (address < 0x8000)
+			return memoryLayout.romBankSwitch[address - 0x4000];
+		if (address < 0xA000)
+			return memoryLayout.vram[address - 0x8000];
+		if (address < 0xC000) {
+			if (externalRamSize == 0)
+				return 0xFF;
+			return memoryLayout.externalRam[address - 0xA000];
+		}
+		if (address < 0xD000)
+			return memoryLayout.memoryBank1[address - 0xC000];
+		if (address < 0xE000)
+			return memoryLayout.memoryBank2[address - 0xD000];
+		if (address < 0xFE00)
+			return memoryLayout.memoryBank1[address - 0xE000];
+		if (address < 0xFEA0)
+			return memoryLayout.oam[address - 0xFE00];
+		if (address < 0xFF00) {
+			if ((memoryLayout.STAT & 0x03) == 2 || (memoryLayout.STAT & 0x03) == 3)
+				return 0xFF;
+			return 0x00;
+		}
+		if (address < 0xFF80)
+			switch (address) {
+			case 0xFF00:
+				return memoryLayout.JOYP;
+			case 0xFF01:
+				return memoryLayout.SB;
+			case 0xFF02:
+				return memoryLayout.SC;
+			// Timer registers
+			case 0xFF04:
+				return memoryLayout.DIV;
+			case 0xFF05:
+				return memoryLayout.TIMA;
+			case 0xFF06:
+				return memoryLayout.TMA;
+			case 0xFF07:
+				return memoryLayout.TAC;
+			// Interrupt flag
+			case 0xFF0F:
+				return memoryLayout.IF;
+			// Sound registers
+			case 0xFF10:
+				return memoryLayout.NR10;
+			case 0xFF11:
+				return memoryLayout.NR11;
+			case 0xFF12:
+				return memoryLayout.NR12;
+			case 0xFF13:
+				return memoryLayout.NR13;
+			case 0xFF14:
+				return memoryLayout.NR14;
+			case 0xFF16:
+				return memoryLayout.NR21;
+			case 0xFF17:
+				return memoryLayout.NR22;
+			case 0xFF18:
+				return memoryLayout.NR23;
+			case 0xFF19:
+				return memoryLayout.NR24;
+			case 0xFF1A:
+				return memoryLayout.NR30;
+			case 0xFF1B:
+				return memoryLayout.NR31;
+			case 0xFF1C:
+				return memoryLayout.NR32;
+			case 0xFF1D:
+				return memoryLayout.NR33;
+			case 0xFF1E:
+				return memoryLayout.NR34;
+			case 0xFF20:
+				return memoryLayout.NR41;
+			case 0xFF21:
+				return memoryLayout.NR42;
+			case 0xFF22:
+				return memoryLayout.NR43;
+			case 0xFF23:
+				return memoryLayout.NR44;
+			case 0xFF24:
+				return memoryLayout.NR50;
+			case 0xFF25:
+				return memoryLayout.NR51;
+			case 0xFF26:
+				return memoryLayout.NR52;
+			// PPU registers
+			case 0xFF40:
+				return memoryLayout.LCDC;
+			case 0xFF41:
+				return memoryLayout.STAT;
+			case 0xFF42:
+				return memoryLayout.SCY;
+			case 0xFF43:
+				return memoryLayout.SCX;
+			case 0xFF44:
+				return memoryLayout.LY;
+			case 0xFF45:
+				return memoryLayout.LYC;
+			case 0xFF46:
+				return memoryLayout.DMA;
+			case 0xFF47:
+				return memoryLayout.BGP;
+			case 0xFF48:
+				return memoryLayout.OBP0;
+			case 0xFF49:
+				return memoryLayout.OBP1;
+			case 0xFF4A:
+				return memoryLayout.WY;
+			case 0xFF4B:
+				return memoryLayout.WX;

-		return memoryLayout.memory[address];
+			default:
+				if (address >= 0xFF30 && address <= 0xFF3F) {
+					return memoryLayout.waveRam[address - 0xFF30];
+				}
+				return 0xFF;
+			}
+		if (address < 0xFFFF)
+			return memoryLayout.specialRam[address - 0xFF80];
+		//0xFFFF
+		return memoryLayout.IE;
 	}

-	Byte& operator[](const uint32_t address) {
-		if (address >= 0xE000 && address < 0xFE00)
-			return memoryLayout.echoRam[address - 0x2000];
+	//write
+	Byte& operator[](const Word address) {
 		if (address < 0x0100 && bootromLoaded)
 			return bootrom[address];
+		if (address < 0x8000)
+			return (*MBCRead(address));
+		if (address < 0xA000)
+			return memoryLayout.vram[address - 0x8000];
+		if (address < 0xC000)
+			return memoryLayout.externalRam[address - 0xA000];
+		if (address < 0xD000)
+			return memoryLayout.memoryBank1[address - 0xC000];
+		if (address < 0xE000)
+			return memoryLayout.memoryBank2[address - 0xD000];
+		if (address < 0xFE00)
+			return memoryLayout.memoryBank1[address - 0xE000];
+		if (address < 0xFEA0)
+			return memoryLayout.oam[address - 0xFE00];
+		if (address < 0xFF00)
+			return memoryLayout.notUsable[address - 0xFEA0];
+		if (address < 0xFF80)
+			switch (address) {
+			case 0xFF00:
+				return memoryLayout.JOYP;
+			case 0xFF01:
+				return memoryLayout.SB;
+			case 0xFF02:
+				return memoryLayout.SC;
+			case 0xFF04:
+				return memoryLayout.DIV;
+			// Timer registers
+			case 0xFF05:
+				return memoryLayout.TIMA;
+			// The address 0xFF15 is mentioned as unused, possibly a mistake? Original has TMA = 0xFF06 typically.
+			case 0xFF06:
+				return memoryLayout.TMA;
+			case 0xFF07:
+				return memoryLayout.TAC;
+			// Interrupt flag
+			case 0xFF0F:
+				return memoryLayout.IF;
+			// Sound registers
+			case 0xFF10:
+				return memoryLayout.NR10;
+			case 0xFF11:
+				return memoryLayout.NR11;
+			case 0xFF12:
+				return memoryLayout.NR12;
+			case 0xFF13:
+				return memoryLayout.NR13;
+			case 0xFF14:
+				return memoryLayout.NR14;
+			case 0xFF16:
+				return memoryLayout.NR21;
+			case 0xFF17:
+				return memoryLayout.NR22;
+			case 0xFF18:
+				return memoryLayout.NR23;
+			case 0xFF19:
+				return memoryLayout.NR24;
+			case 0xFF1A:
+				return memoryLayout.NR30;
+			case 0xFF1B:
+				return memoryLayout.NR31;
+			case 0xFF1C:
+				return memoryLayout.NR32;
+			case 0xFF1D:
+				return memoryLayout.NR33;
+			case 0xFF1E:
+				return memoryLayout.NR34;
+			case 0xFF20:
+				return memoryLayout.NR41;
+			case 0xFF21:
+				return memoryLayout.NR42;
+			case 0xFF22:
+				return memoryLayout.NR43;
+			case 0xFF23:
+				return memoryLayout.NR44;
+			case 0xFF24:
+				return memoryLayout.NR50;
+			case 0xFF25:
+				return memoryLayout.NR51;
+			case 0xFF26:
+				return memoryLayout.NR52;
+			// PPU registers
+			case 0xFF40:
+				return memoryLayout.LCDC;
+			case 0xFF41:
+				return memoryLayout.STAT;
+			case 0xFF42:
+				return memoryLayout.SCY;
+			case 0xFF43:
+				return memoryLayout.SCX;
+			case 0xFF44:
+				return memoryLayout.LY;
+			case 0xFF45:
+				return memoryLayout.LYC;
+			case 0xFF46:
+				return memoryLayout.DMA;
+			case 0xFF47:
+				return memoryLayout.BGP;
+			case 0xFF48:
+				return memoryLayout.OBP0;
+			case 0xFF49:
+				return memoryLayout.OBP1;
+			case 0xFF4A:
+				return memoryLayout.WY;
+			case 0xFF4B:
+				return memoryLayout.WX;

-		return memoryLayout.memory[address];
+			default:
+				if (address >= 0xFF30 && address <= 0xFF3F) {
+					return memoryLayout.waveRam[address - 0xFF30];
+				}
+				return dummyVal;
+			}
+		if (address < 0xFFFF)
+			return memoryLayout.specialRam[address - 0xFF80];
+		//0xFFFF
+		return memoryLayout.IE;
 	}
 };

--- a/src/defines.hpp
+++ b/src/defines.hpp
@@ -32,6 +32,7 @@
 #define SCREEN_BPP 3

 #define ROM_BANK_SIZE 0x4000
+#define RAM_BANK_SIZE 0x2000

 #define SCANLINES_PER_FRAME 154
 #define SCANLINE_DURATION 456
--- a/src/extendedOpcodeResolver.cpp
+++ b/src/extendedOpcodeResolver.cpp
@@ -3,7 +3,7 @@
 void GameBoy::extendedOpcodeResolver() {
 	PC += 1;

-	switch (addressSpace[PC]) {
+	switch (readOnlyAddressSpace[PC]) {
 	case 0x00:
 		rlc(BC.hi);
 		PC += 1;
@@ -425,7 +425,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x46:
-		bit(0, addressSpace[HL.reg]);
+		bit(0, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -473,7 +473,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x4E:
-		bit(1, addressSpace[HL.reg]);
+		bit(1, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -521,7 +521,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x56:
-		bit(2, addressSpace[HL.reg]);
+		bit(2, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -569,7 +569,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x5E:
-		bit(3, addressSpace[HL.reg]);
+		bit(3, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -617,7 +617,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x66:
-		bit(4, addressSpace[HL.reg]);
+		bit(4, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -665,7 +665,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x6E:
-		bit(5, addressSpace[HL.reg]);
+		bit(5, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -713,7 +713,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x76:
-		bit(6, addressSpace[HL.reg]);
+		bit(6, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
@@ -761,7 +761,7 @@ void GameBoy::extendedOpcodeResolver() {
 		break;

 	case 0x7E:
-		bit(7, addressSpace[HL.reg]);
+		bit(7, readOnlyAddressSpace[HL.reg]);
 		PC += 1;
 		addCycles(12);
 		break;
--- a/src/gameboy.cpp
+++ b/src/gameboy.cpp
@@ -13,10 +13,11 @@ void GameBoy::start(std::string bootrom, std::string game) {
 	addressSpace.loadBootrom(bootrom);
 	addressSpace.loadGame(game);
 	addressSpace.determineMBCInfo();
+	addressSpace.createRamBank();

 	//init some registers that won't otherwise by set
-	(*JOYP) = 0xCF;
-	(*SC) = 0x7E;
+	addressSpace.memoryLayout.JOYP = 0xCF;
+	addressSpace.memoryLayout.SC = 0x7E;

 	bool quit = false;

@@ -28,29 +29,34 @@ void GameBoy::start(std::string bootrom, std::string game) {
 			if (event.type == SDL_QUIT) {
 				quit = true;
 			}
+			if (event.type == SDL_KEYUP) {
+				display = true;
+			}
 		}

 		while (!rendered) {
 			if (PC > 0xFF && addressSpace.getBootromState()) {
 				addressSpace.unmapBootrom();
 			}
-			ppuEnabled = (*LCDC) & 0x80;
+			ppuEnabled = addressSpace.memoryLayout.LCDC & 0x80;

-			if (PC >= 0xe0)
-				display = true;
-			if (display) {
-				printf("Cycles: %lu, Opcode: 0x%.2x PPU cycles: %lu, PPMode: %d\n", cycles, addressSpace[PC],
-				       cyclesSinceLastScanline(), currentMode);
-				printf("PC:0x%.2x, SP:0x%.2x\n", PC, SP);
-				printf("AF:0x%.4x, BC:0x%.4x\n", AF.reg, BC.reg);
-				printf("DE:0x%.4x, HL:0x%.4x\n", DE.reg, HL.reg);
-				printf("IME:%d IF:0x%.2x IE:0x%.2x\n", IME, (*IF), (*IE));
-				printf("LCDC:%.2x STAT:0x%.2x LY:%d LYC:%d\n", (*LCDC), (*STAT), (*LY), (*LYC));
-				printf("Cart type: 0x%.2x\n", addressSpace.game[0x147]);
-				printf("\n");
-			}
+			// if (PC == 0x100)
+			// 	display = true;
+			// if (display) {
+			// 	printf("Cycles: %lu, Opcode: 0x%.2x PPU cycles: %lu, PPMode: %d\n", cycles, readOnlyAddressSpace[PC],
+			// 	       cyclesSinceLastScanline(), currentMode);
+			// 	printf("AF:0x%.4x, BC:0x%.4x\n", AF.reg, BC.reg);
+			// 	printf("DE:0x%.4x, HL:0x%.4x\n", DE.reg, HL.reg);
+			// 	printf("IME:%d IF:0x%.2x IE:0x%.2x\n", IME, (*IF), (*IE));
+			// 	printf("PC:0x%.4x, SP:0x%.4x\n", PC, SP);
+			// 	printf("LCDC:%.2x STAT:0x%.2x LY:%d LYC:%d\n", (*LCDC), (*STAT), (*LY), (*LYC));
+			// 	printf("\n");
+			// }
+			// if (PC >= 0xf000)
+			// 	exit(1);

 			opcodeResolver();
+			addressSpace.MBCUpdate();
 			interruptHandler();
 			timingHandler();
 			if (ppuEnabled) {
@@ -60,8 +66,8 @@ void GameBoy::start(std::string bootrom, std::string game) {
 				ppuCycles = 2;
 				lastScanline = 0;
 				lastRefresh = 0;
-				(*LY) = 0x00;
-				(*STAT) &= 0xfc;
+				addressSpace.memoryLayout.LY = 0x00;
+				addressSpace.memoryLayout.STAT &= 0xfc;
 			}
 		}
 		rendered = false;
--- a/src/gameboy.hpp
+++ b/src/gameboy.hpp
@@ -46,61 +46,7 @@ class GameBoy {
 	Word PC = 0x0000; //program counter

 	AddressSpace addressSpace;
-
-	//General purpose hardware registers
-	Byte* const JOYP = &addressSpace[0xFF00];
-	Byte* const SB = &addressSpace[0xFF01];
-	Byte* const SC = &addressSpace[0xFF02];
-	Byte* const DIV = &addressSpace[0xFF04];
-
-	//Timer registers
-	Byte* const TIMA = &addressSpace[0xFF05];
-	Byte* const TMA = &addressSpace[0xFF15]; //unused
-	Byte* const TAC = &addressSpace[0xFF16];
-
-	//interrupt flag and enable
-	Byte* const IF = &addressSpace[0xFF0F];
-	Byte* const IE = &addressSpace[0xFFFF];
-
-	//Sound registers
-	Byte* const NR10 = &addressSpace[0xFF10];
-	Byte* const NR11 = &addressSpace[0xFF11];
-	Byte* const NR12 = &addressSpace[0xFF12];
-	Byte* const NR13 = &addressSpace[0xFF13];
-	Byte* const NR14 = &addressSpace[0xFF14];
-	Byte* const NR20 = &addressSpace[0xFF15]; //unused
-	Byte* const NR21 = &addressSpace[0xFF16];
-	Byte* const NR22 = &addressSpace[0xFF17];
-	Byte* const NR23 = &addressSpace[0xFF18];
-	Byte* const NR24 = &addressSpace[0xFF19];
-	Byte* const NR30 = &addressSpace[0xFF1A];
-	Byte* const NR31 = &addressSpace[0xFF1B];
-	Byte* const NR32 = &addressSpace[0xFF1C];
-	Byte* const NR33 = &addressSpace[0xFF1D];
-	Byte* const NR34 = &addressSpace[0xFF1E];
-	Byte* const NR40 = &addressSpace[0xFF1F]; //unused
-	Byte* const NR41 = &addressSpace[0xFF20];
-	Byte* const NR42 = &addressSpace[0xFF21];
-	Byte* const NR43 = &addressSpace[0xFF22];
-	Byte* const NR44 = &addressSpace[0xFF23];
-	Byte* const NR50 = &addressSpace[0xFF24];
-	Byte* const NR51 = &addressSpace[0xFF25];
-	Byte* const NR52 = &addressSpace[0xFF26];
-	Byte* const waveRam = &addressSpace[0xFF30]; //WaveRam[0x10]
-
-	//PPU registers
-	Byte* const LCDC = &addressSpace[0xFF40];
-	Byte* const STAT = &addressSpace[0xFF41];
-	Byte* const SCY = &addressSpace[0xFF42];
-	Byte* const SCX = &addressSpace[0xFF43];
-	Byte* const LY = &addressSpace[0xFF44];
-	Byte* const LYC = &addressSpace[0xFF45];
-	Byte* const DMA = &addressSpace[0xFF46];
-	Byte* const BGP = &addressSpace[0xFF47];
-	Byte* const OBP0 = &addressSpace[0xFF48];
-	Byte* const OBP1 = &addressSpace[0xFF49];
-	Byte* const WY = &addressSpace[0xFF4A];
-	Byte* const WX = &addressSpace[0xFF4B];
+	const AddressSpace& readOnlyAddressSpace = addressSpace;

 	PPUMode currentMode = PPUMode::mode0;

@@ -114,8 +60,6 @@ class GameBoy {
 	uint32_t frameTime = 0;
 	const int frameDelay = 1000 / V_SYNC;

-	bool testMBCWrite(const Byte& address);
-
 	void opcodeResolver();
 	void incLY();
 	void ppuUpdate();
@@ -131,7 +75,7 @@ class GameBoy {

 	void interruptHandler();
 	bool testInterruptEnabled(Byte interrupt) const;
-	void resetInterrupt(Byte interrupt) const;
+	void resetInterrupt(Byte interrupt);

 	void VBlankHandle();
 	void LCDStatHandle();
@@ -162,8 +106,8 @@ class GameBoy {
 	void xorBitwise(T& dest, T src);
 	void bit(Byte testBit, Byte reg);
 	void extendedOpcodeResolver();
-	static void set(const uint8_t testBit, uint8_t& reg);
-	static void res(const uint8_t testBit, uint8_t& reg);
+	static void set(uint8_t testBit, uint8_t& reg);
+	static void res(uint8_t testBit, uint8_t& reg);
 	template <typename T>
 	void jp(T address);
 	template <typename T>
--- a/src/interupts.cpp
+++ b/src/interupts.cpp
@@ -2,27 +2,32 @@
 #include "gameboy.hpp"

 bool GameBoy::testInterruptEnabled(const Byte interrupt) const {
-	return (*IE) & static_cast<Byte>(1 << interrupt);
+	return readOnlyAddressSpace.memoryLayout.IE & static_cast<Byte>(1 << interrupt);
 }

-void GameBoy::resetInterrupt(const Byte interrupt) const {
-	*IF &= ~(1 << interrupt);
-	*IF |= 0xE0;
+void GameBoy::resetInterrupt(const Byte interrupt) {
+	addressSpace.memoryLayout.IF &= ~(1 << interrupt);
+	addressSpace.memoryLayout.IF |= 0xE0;
 }

 void GameBoy::interruptHandler() {
 	if (!IME)
 		return;

-	if (*IF & static_cast<Byte>(1 << VBLANK_INTERRUPT) && testInterruptEnabled(VBLANK_INTERRUPT))
+	if (readOnlyAddressSpace.memoryLayout.IF & static_cast<Byte>(1 << VBLANK_INTERRUPT) && testInterruptEnabled(
+		VBLANK_INTERRUPT))
 		VBlankHandle();
-	if (*IF & static_cast<Byte>(1 << LCD_STAT_INTERRUPT) && testInterruptEnabled(LCD_STAT_INTERRUPT))
+	if (readOnlyAddressSpace.memoryLayout.IF & static_cast<Byte>(1 << LCD_STAT_INTERRUPT) && testInterruptEnabled(
+		LCD_STAT_INTERRUPT))
 		LCDStatHandle();
-	if (*IF & static_cast<Byte>(1 << TIMER_INTERRUPT) && testInterruptEnabled(TIMER_INTERRUPT))
+	if (readOnlyAddressSpace.memoryLayout.IF & static_cast<Byte>(1 << TIMER_INTERRUPT) && testInterruptEnabled(
+		TIMER_INTERRUPT))
 		timerHandle();
-	if (*IF & static_cast<Byte>(1 << SERIAL_INTERRUPT) && testInterruptEnabled(SERIAL_INTERRUPT))
+	if (readOnlyAddressSpace.memoryLayout.IF & static_cast<Byte>(1 << SERIAL_INTERRUPT) && testInterruptEnabled(
+		SERIAL_INTERRUPT))
 		serialHandle();
-	if (*IF & static_cast<Byte>(1 << JOYPAD_INTERRUPT) && testInterruptEnabled(JOYPAD_INTERRUPT))
+	if (readOnlyAddressSpace.memoryLayout.IF & static_cast<Byte>(1 << JOYPAD_INTERRUPT) && testInterruptEnabled(
+		JOYPAD_INTERRUPT))
 		joypadHandle();
 }

--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4,7 +4,7 @@
 int main(int argc, char** argv) {
 	auto* gb = new GameBoy();
 	gb->SDL2setup();
-	gb->start("../dmg_boot.bin", "../roms/cpu_instrs.gb");
+	gb->start("../dmg_boot.bin", "../roms/03-op_sp,hl.gb");
 	gb->SDL2destroy();
 	delete gb;

--- a/src/mbc.cpp
+++ b/src/mbc.cpp
@@ -1,10 +1,9 @@
 #include "addressSpace.hpp"
-#include "gameboy.hpp"

 void AddressSpace::determineMBCInfo() {
 	MBC = static_cast<MBCType>(memoryLayout.romBank0[0x147]);
 	romSize = 32768 * (1 << memoryLayout.romBank0[0x147]);
-	romBanks = (1 << (memoryLayout.romBank0[0x147] + 1));
+	romBanks = 1 << (memoryLayout.romBank0[0x147] + 1);

 	switch (memoryLayout.romBank0[0x0149]) {
 	case 0x02:
@@ -29,16 +28,90 @@ void AddressSpace::determineMBCInfo() {
 		break;
 	}

-	if (MBC == MBC2 || MBC2Battery) {
+	if (MBC == MBC2 || MBC == MBC2Battery) {
 		//only the lower 4 bits are usable
 		externalRamSize = 512;
 	}
 }

-bool GameBoy::testMBCWrite(const Byte& address) {
-	const Byte* ptr = &address;
-	if (ptr >= &addressSpace[0x0] && ptr <= &addressSpace[0x7FFF])
+bool AddressSpace::testMBCWrite(const Word address) {
+	if (address <= 0x7FFF)
 		return true;
 	return false;
 }

+Byte* AddressSpace::MBCRead(const Word address) {
+	if (MBC == MBC1) {
+		if (address <= 0x1FFF)
+			return &ramEnable;
+		if (address <= 0x3FFF)
+			return &romBankRegister;
+		if (address <= 0x5FFF)
+			return &twoBitBankRegister;
+		if (address <= 0x7FFF)
+			return &romRamSelect;
+	}
+	if (MBC == MBC1Ram || MBC == MBC1RamBattery) {
+		if (address <= 0x1FFF)
+			return &ramEnable;
+		//bits 0-4
+		if (address <= 0x3FFF)
+			return &romBankRegister;
+		if (address <= 0x5FFF) {
+			return &twoBitBankRegister;
+		}
+		if (address <= 0x7FFF)
+			return &romRamSelect;
+	}
+	return &dummyVal;
+}
+
+void AddressSpace::MBCUpdate() {
+	if (MBC == MBC1) {
+		//TODO: multicart roms need to be able to switch the first rom bank as well
+		//see: https://gbdev.io/pandocs/MBC1.html
+
+		//Selected ROM Bank = (Secondary Bank << 5) + ROM Bank
+		romBankRegister &= 0x1F;
+		twoBitBankRegister &= 0x3;
+
+		//512 KiB can only have 8KiB of ram
+		if (romSize > 524288) {
+			if (romBankRegister == 0)
+				selectedRomBank = (twoBitBankRegister << 5) + 1;
+			selectedRomBank = (twoBitBankRegister << 5) + romBankRegister;
+			selectedExternalRamBank = 0;
+		}
+		else {
+			if (romBankRegister == 0)
+				selectedRomBank = 1;
+			else
+				selectedRomBank = romBankRegister;
+			selectedExternalRamBank = twoBitBankRegister;
+		}
+		loadRomBank();
+		loadRamBank();
+	}
+	if (MBC == MBC1Ram || MBC == MBC1RamBattery) {}
+}
+
+void AddressSpace::loadRomBank() {
+	Byte* old = memoryLayout.romBankSwitch;
+	memoryLayout.romBankSwitch = game.data() + (ROM_BANK_SIZE * selectedRomBank);
+	if (old != memoryLayout.romBankSwitch)
+		printf("\n");
+}
+
+void AddressSpace::createRamBank() {
+	if (externalRamSize)
+		cartridgeRam = new Byte[externalRamSize];
+}
+
+void AddressSpace::loadRamBank() {
+	Byte* old = memoryLayout.externalRam;
+	if (cartridgeRam != nullptr)
+		memoryLayout.externalRam = cartridgeRam + (RAM_BANK_SIZE * selectedExternalRamBank);
+	if (old != memoryLayout.externalRam)
+		printf("\n");
+}
+
--- a/src/opcodeResolver.cpp
+++ b/src/opcodeResolver.cpp
@@ -16,28 +16,28 @@ Word GameBoy::getWordPC() {
 	RegisterPair word = {0};

 	//remember little endianness
-	word.lo = addressSpace[PC + 1];
-	word.hi = addressSpace[PC + 2];
+	word.lo = readOnlyAddressSpace[PC + 1];
+	word.hi = readOnlyAddressSpace[PC + 2];

 	return word.reg;
 }

 Byte GameBoy::getBytePC() {
-	return addressSpace[PC + 1];
+	return readOnlyAddressSpace[PC + 1];
 }

 Word GameBoy::getWordSP() {
 	RegisterPair word = {0};

 	//remember little endianness
-	word.lo = addressSpace[SP++];
-	word.hi = addressSpace[SP++];
+	word.lo = readOnlyAddressSpace[SP++];
+	word.hi = readOnlyAddressSpace[SP++];

 	return word.reg;
 }

 Byte GameBoy::getByteSP() {
-	return addressSpace[SP++];
+	return readOnlyAddressSpace[SP++];
 }

 void GameBoy::ret() {
@@ -47,8 +47,8 @@ void GameBoy::ret() {
 template <typename T>
 void GameBoy::ld(T& dest, T src) {
 	if constexpr (std::is_same_v<T, Byte>) {
-		if (&dest == DIV) {
-			*DIV = 0x00;
+		if (&dest == &addressSpace.memoryLayout.DIV) {
+			addressSpace.memoryLayout.DIV = 0x00;
 			lastDivUpdate = cycles;
 		}
 		else {
@@ -90,7 +90,7 @@ void GameBoy::add(T& reg, T value) {
 		else
 			resetFlag(HALFCARRY_FLAG);
 		//halfcarry test https://robdor.com/2016/08/10/gameboy-emulator-half-carry-flag/
-		if ((((value & 0xFFFF) + (reg & 0xFFFF)) & 0x10000) == 0x10000)
+		if ((static_cast<unsigned>(value) + static_cast<unsigned>(reg)) & 0x10000)
 			setFlag(CARRY_FLAG);
 		else
 			resetFlag(CARRY_FLAG);
@@ -98,10 +98,12 @@ void GameBoy::add(T& reg, T value) {

 	reg += value;

-	if (reg == 0)
-		setFlag(ZERO_FLAG);
-	else
-		resetFlag(ZERO_FLAG);
+	if (sizeof(reg) == sizeof(Byte)) {
+		if (reg == 0)
+			setFlag(ZERO_FLAG);
+		else
+			resetFlag(ZERO_FLAG);
+	}

 	resetFlag(SUBTRACT_FLAG);
 }
@@ -225,6 +227,8 @@ void GameBoy::orBitwise(T& dest, T src) {

 	if (dest == 0)
 		setFlag(ZERO_FLAG);
+	else
+		resetFlag(ZERO_FLAG);

 	resetFlag(SUBTRACT_FLAG);
 	resetFlag(HALFCARRY_FLAG);
@@ -237,6 +241,8 @@ void GameBoy::andBitwise(T& dest, T src) {

 	if (dest == 0)
 		setFlag(ZERO_FLAG);
+	else
+		resetFlag(ZERO_FLAG);

 	resetFlag(SUBTRACT_FLAG);
 	setFlag(HALFCARRY_FLAG);
@@ -249,6 +255,8 @@ void GameBoy::xorBitwise(T& dest, T src) {

 	if (dest == 0)
 		setFlag(ZERO_FLAG);
+	else
+		resetFlag(ZERO_FLAG);

 	resetFlag(SUBTRACT_FLAG);
 	resetFlag(CARRY_FLAG);
@@ -473,7 +481,7 @@ void GameBoy::rr(Byte& reg) {
 	reg >>= 1;

 	if (getFlag(CARRY_FLAG))
-		AF.hi |= 0x80;
+		reg |= 0x80;

 	if (lsb)
 		setFlag(CARRY_FLAG);
@@ -628,6 +636,7 @@ void GameBoy::srl(Byte& reg) {
 template <typename T>
 void GameBoy::pop(T& reg) {
 	reg = getWordSP();
+	AF.reg &= 0xFFF0;
 }

 template <typename T>
@@ -636,9 +645,9 @@ void GameBoy::push(T reg) {
 	RegisterPair temp = {0};
 	temp.lo = reg & 0xFF;
 	temp.hi = reg >> 8;
-	SP--;
+	SP -= 1;
 	addressSpace[SP] = temp.hi;
-	SP--;
+	SP -= 1;
 	addressSpace[SP] = temp.lo;
 }

@@ -678,9 +687,9 @@ void GameBoy::ccf() {
 void GameBoy::stop() {}

 void GameBoy::opcodeResolver() {
-	if (addressSpace[PC] != 0xCB) {
+	if (readOnlyAddressSpace[PC] != 0xCB) {
 		bool jumped;
-		switch (addressSpace[PC]) {
+		switch (readOnlyAddressSpace[PC]) {
 		case 0x00:
 			//NOP
 			PC += 1;
@@ -742,7 +751,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x0A:
-			ld(AF.hi, addressSpace[BC.reg]);
+			ld(AF.hi, readOnlyAddressSpace[BC.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -790,13 +799,13 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x12:
-			ld(addressSpace[BC.reg], AF.hi);
+			ld(addressSpace[DE.reg], AF.hi);
 			PC += 1;
 			addCycles(8);
 			break;

 		case 0x13:
-			DE.reg++; //no flags change no just inc it manually
+			DE.reg += 1; //no flags change no just inc it manually
 			PC += 1;
 			addCycles(8);
 			break;
@@ -837,7 +846,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x1A:
-			ld(AF.hi, addressSpace[DE.reg]);
+			ld(AF.hi, readOnlyAddressSpace[DE.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -891,7 +900,7 @@ void GameBoy::opcodeResolver() {

 		case 0x22:
 			ld(addressSpace[HL.reg], AF.hi);
-			HL.reg++;
+			HL.reg += 1;
 			PC += 1;
 			addCycles(8);
 			break;
@@ -944,7 +953,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x2A:
-			ld(AF.hi, addressSpace[HL.reg]);
+			ld(AF.hi, readOnlyAddressSpace[HL.reg]);
 			HL.reg += 1;
 			PC += 1;
 			addCycles(8);
@@ -963,7 +972,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x2D:
-			dec(HL.hi);
+			dec(HL.lo);
 			PC += 1;
 			addCycles(4);
 			break;
@@ -999,7 +1008,7 @@ void GameBoy::opcodeResolver() {

 		case 0x32:
 			ld(addressSpace[HL.reg], AF.hi);
-			HL.reg--;
+			HL.reg -= 1;
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1052,14 +1061,14 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x3A:
-			ld(AF.hi, addressSpace[HL.reg]);
+			ld(AF.hi, readOnlyAddressSpace[HL.reg]);
 			HL.reg -= 1;
 			PC += 1;
 			addCycles(8);
 			break;

 		case 0x3B:
-			SP--;
+			SP -= 1;
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1125,7 +1134,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x46:
-			ld(BC.hi, addressSpace[HL.reg]);
+			ld(BC.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1173,7 +1182,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x4E:
-			ld(BC.lo, addressSpace[HL.reg]);
+			ld(BC.lo, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1221,7 +1230,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x56:
-			ld(DE.hi, addressSpace[HL.reg]);
+			ld(DE.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1269,7 +1278,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x5E:
-			ld(DE.lo, addressSpace[HL.reg]);
+			ld(DE.lo, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1317,7 +1326,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x66:
-			ld(HL.hi, addressSpace[HL.reg]);
+			ld(HL.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1365,7 +1374,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x6E:
-			ld(HL.lo, addressSpace[HL.reg]);
+			ld(HL.lo, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1461,7 +1470,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x7E:
-			ld(AF.hi, addressSpace[HL.reg]);
+			ld(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1509,7 +1518,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x86:
-			add(AF.hi, addressSpace[HL.reg]);
+			add(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1557,7 +1566,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x8E:
-			adc(AF.hi, addressSpace[HL.reg]);
+			adc(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1605,7 +1614,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x96:
-			sub(addressSpace[HL.reg]);
+			sub(readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1653,7 +1662,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0x9E:
-			sbc(addressSpace[HL.reg]);
+			sbc(readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1701,7 +1710,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xA6:
-			andBitwise(AF.hi, addressSpace[HL.reg]);
+			andBitwise(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1749,7 +1758,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xAE:
-			xorBitwise(AF.hi, addressSpace[HL.reg]);
+			xorBitwise(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1797,7 +1806,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xB6:
-			orBitwise(AF.hi, addressSpace[HL.reg]);
+			orBitwise(AF.hi, readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -1845,7 +1854,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xBE:
-			cp(addressSpace[HL.reg]);
+			cp(readOnlyAddressSpace[HL.reg]);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -2091,7 +2100,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xE2:
-			ld(addressSpace[BC.lo + 0xFF00], AF.hi);
+			ld(addressSpace[0xFF00 + BC.lo], AF.hi);
 			PC += 1;
 			addCycles(8);
 			break;
@@ -2115,20 +2124,19 @@ void GameBoy::opcodeResolver() {

 		case 0xE8:
 			{
-				const auto immediate = static_cast<int8_t>(getBytePC());
-				const Word result = SP + static_cast<int16_t>(immediate);
+				const int16_t immediate = static_cast<int8_t>(getBytePC());

-				if (((SP ^ immediate ^ result) & 0x10) != 0)
+				if ((SP & 0xF) + (immediate & 0xF) > 0xF)
 					setFlag(HALFCARRY_FLAG);
 				else
 					resetFlag(HALFCARRY_FLAG);

-				if (((SP ^ immediate ^ result) & 0x100) != 0)
+				if ((SP & 0xFF) + (immediate & 0xFF) > 0xFF)
 					setFlag(CARRY_FLAG);
 				else
 					resetFlag(CARRY_FLAG);

-				SP = result;
+				SP += immediate;

 				resetFlag(ZERO_FLAG);
 				resetFlag(SUBTRACT_FLAG);
@@ -2161,7 +2169,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xF0:
-			ld(AF.hi, addressSpace[0xFF00 + getBytePC()]);
+			ld(AF.hi, readOnlyAddressSpace[0xFF00 + getBytePC()]);
 			PC += 2;
 			addCycles(12);
 			break;
@@ -2173,7 +2181,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xF2:
-			ld(AF.hi, addressSpace[0xFF00 + BC.lo]);
+			ld(AF.hi, readOnlyAddressSpace[0xFF00 + BC.lo]);
 			PC += 1;
 			addCycles(12);
 			break;
@@ -2203,20 +2211,20 @@ void GameBoy::opcodeResolver() {

 		case 0xF8:
 			{
-				const auto n = static_cast<int8_t>(getBytePC());
-				const Word result = SP + n;
+				const int16_t immediate = static_cast<int8_t>(getBytePC());
+				HL.reg = SP + immediate;

-				//halfcarry test https://robdor.com/2016/08/10/gameboy-emulator-half-carry-flag/
-				if ((((result & 0xF) + (HL.reg & 0xF)) & 0x10) == 0x10)
+				if ((SP & 0xF) + (immediate & 0xF) > 0xF)
 					setFlag(HALFCARRY_FLAG);
 				else
 					resetFlag(HALFCARRY_FLAG);
-				//halfcarry test https://robdor.com/2016/08/10/gameboy-emulator-half-carry-flag/
-				if ((((result & 0xFF) + (HL.reg & 0xFF)) & 0x100) == 0x100)
+
+
+				if ((SP & 0xFF) + (immediate & 0xFF) > 0xFF)
 					setFlag(CARRY_FLAG);
 				else
 					resetFlag(CARRY_FLAG);
-				HL.reg = result; // Load the result into HL
+

 				resetFlag(ZERO_FLAG);
 				resetFlag(SUBTRACT_FLAG);
@@ -2233,7 +2241,7 @@ void GameBoy::opcodeResolver() {
 			break;

 		case 0xFA:
-			ld(AF.hi, addressSpace[getWordPC()]);
+			ld(AF.hi, readOnlyAddressSpace[getWordPC()]);
 			PC += 3;
 			addCycles(16);
 			break;
--- a/src/ppu.cpp
+++ b/src/ppu.cpp
@@ -8,25 +8,28 @@ void GameBoy::ppuUpdate() {
 	//test for HBlank
 	checkPPUMode();

-	if ((*LY) == (*LYC) || (*STAT) & (1 << 6)) {
+	if (readOnlyAddressSpace.memoryLayout.LY == readOnlyAddressSpace.memoryLayout.LYC || readOnlyAddressSpace.
+		memoryLayout.STAT & (1 << 6)) {
 		// Request STAT interrupt if LY matches LYC
 		// bug on DMG models triggers a STAT interrupt anytime the STAT register is written
 		// Road Rage and Zerd no Denetsu rely on this
-		(*STAT) |= (1 << 2);
+		addressSpace.memoryLayout.STAT |= (1 << 2);
 	}
 	else {
-		(*STAT) &= ~(1 << 2);
+		addressSpace.memoryLayout.STAT &= ~(1 << 2);
 	}

 	// Check for STAT interrupts and request if needed (e.g., when entering specific modes)
-	bool hBlankInterruptEnabled = (*STAT) & (1 << 3);
-	bool vBlankInterruptEnabled = (*STAT) & (1 << 4); /* Determine if VBlank interrupt is enabled */
-	bool oamInterruptEnabled = (*STAT) & (1 << 5); /* Determine if OAM Search interrupt is enabled */
+	bool hBlankInterruptEnabled = readOnlyAddressSpace.memoryLayout.STAT & (1 << 3);
+	bool vBlankInterruptEnabled = readOnlyAddressSpace.memoryLayout.STAT & (1 << 4);
+	/* Determine if VBlank interrupt is enabled */
+	bool oamInterruptEnabled = readOnlyAddressSpace.memoryLayout.STAT & (1 << 5);
+	/* Determine if OAM Search interrupt is enabled */

 	if (currentMode == PPUMode::mode0 && hBlankInterruptEnabled ||
 		currentMode == PPUMode::mode1 && vBlankInterruptEnabled ||
 		currentMode == PPUMode::mode2 && oamInterruptEnabled) {
-		*IF |= 0x2;
+		addressSpace.memoryLayout.IF |= 0x2;
 	}
 }

@@ -58,16 +61,16 @@ void GameBoy::checkPPUMode() {
 }

 void GameBoy::incLY() {
-	(*LY)++;
+	addressSpace.memoryLayout.LY += 1;
 	setPPUMode(PPUMode::mode2);
-	if ((*LY) > SCANLINES_PER_FRAME - 1) {
-		(*LY) = 0;
+	if (addressSpace.memoryLayout.LY > SCANLINES_PER_FRAME - 1) {
+		addressSpace.memoryLayout.LY = 0;
 	}
-	else if ((*LY) == 144) {
+	else if (addressSpace.memoryLayout.LY == 144) {
 		// VBlank Period
 		SDL2present();
 		setPPUMode(PPUMode::mode1);
-		*IF |= 0x1;
+		addressSpace.memoryLayout.IF |= 0x1;
 	}
 }

@@ -84,31 +87,31 @@ uint64_t GameBoy::cyclesSinceLastRefresh() const {
 void GameBoy::setPPUMode(const PPUMode mode) {
 	switch (mode) {
 	case PPUMode::mode0:
-		(*STAT) &= ~0x03;
+		addressSpace.memoryLayout.STAT &= ~0x03;
 		currentMode = PPUMode::mode0;
 		break;
 	case PPUMode::mode1:
-		(*STAT) &= ~0x03;
-		(*STAT) |= 0x01;
+		addressSpace.memoryLayout.STAT &= ~0x03;
+		addressSpace.memoryLayout.STAT |= 0x01;
 		currentMode = PPUMode::mode1;
 		break;
 	case PPUMode::mode2:
-		(*STAT) &= ~0x03;
-		(*STAT) |= 0x02;
+		addressSpace.memoryLayout.STAT &= ~0x03;
+		addressSpace.memoryLayout.STAT |= 0x02;
 		currentMode = PPUMode::mode2;
 		break;
 	case PPUMode::mode3:
-		(*STAT) &= ~0x03;
-		(*STAT) |= 0x03;
+		addressSpace.memoryLayout.STAT &= ~0x03;
+		addressSpace.memoryLayout.STAT |= 0x03;
 		currentMode = PPUMode::mode3;
 		break;
 	}
 	//7th bit is unused but always set
-	(*STAT) |= 0x80;
+	addressSpace.memoryLayout.STAT |= 0x80;
 }

 void GameBoy::drawLine() {
-	const uint8_t line = (*LY);
+	const uint8_t line = readOnlyAddressSpace.memoryLayout.LY;

 	// Calculate the starting index of the current scanline in the framebuffer
 	const uint32_t lineStartIndex = line * RESOLUTION_X;
@@ -116,25 +119,27 @@ void GameBoy::drawLine() {
 	// Pointer to the current line's pixel data in the framebuffer
 	uint32_t* currentLinePixels = framebuffer + lineStartIndex;

-	if (!(*LCDC & 0x1)) {
+	if (!(readOnlyAddressSpace.memoryLayout.LCDC & 0x1)) {
 		std::fill_n(currentLinePixels, RESOLUTION_X, 0xFFFFFFFF); // Fill line with white if BG display is off.
 		return;
 	}

-	const uint16_t backgroundMapAddr = (*LCDC & 0x08) ? 0x9C00 : 0x9800;
-	const uint16_t tileDataTableAddr = (*LCDC & 0x10) ? 0x8000 : 0x8800;
-	const bool signedIndex = !(*LCDC & 0x10);
+	const uint16_t backgroundMapAddr = (readOnlyAddressSpace.memoryLayout.LCDC & 0x08) ? 0x9C00 : 0x9800;
+	const uint16_t tileDataTableAddr = (readOnlyAddressSpace.memoryLayout.LCDC & 0x10) ? 0x8000 : 0x8800;
+	const bool signedIndex = !(readOnlyAddressSpace.memoryLayout.LCDC & 0x10);

 	for (int pixel = 0; pixel < RESOLUTION_X; pixel++) {
-		const uint8_t xPos = (pixel + (*SCX)) % 256; // 256 pixels in total BG width
-		const uint8_t yPos = (line + (*SCY)) % 256; // 256 pixels in total BG height
+		const uint8_t xPos = (pixel + readOnlyAddressSpace.memoryLayout.SCX) % 256; // 256 pixels in total BG width
+		const uint8_t yPos = (line + readOnlyAddressSpace.memoryLayout.SCY) % 256; // 256 pixels in total BG height

 		const uint16_t tileRow = (yPos / 8) * 32;
 		const uint16_t tileCol = xPos / 8;
 		const uint16_t tileIndex = tileRow + tileCol;

 		const uint16_t tileAddr = backgroundMapAddr + tileIndex;
-		const int8_t tileID = signedIndex ? static_cast<int8_t>(addressSpace[tileAddr]) : addressSpace[tileAddr];
+		const int8_t tileID = signedIndex
+			                      ? static_cast<int8_t>(readOnlyAddressSpace[tileAddr])
+			                      : addressSpace[tileAddr];

 		uint16_t tileDataAddr;
 		if (signedIndex) {
@@ -145,14 +150,14 @@ void GameBoy::drawLine() {
 		}

 		const uint8_t lineOffset = yPos % 8;
-		const uint8_t tileRowData1 = addressSpace[tileDataAddr + (lineOffset * 2)];
-		const uint8_t tileRowData2 = addressSpace[tileDataAddr + (lineOffset * 2) + 1];
+		const uint8_t tileRowData1 = readOnlyAddressSpace[tileDataAddr + (lineOffset * 2)];
+		const uint8_t tileRowData2 = readOnlyAddressSpace[tileDataAddr + (lineOffset * 2) + 1];

 		const uint8_t colourBit = 7 - (xPos % 8);
 		const uint8_t colourNum = ((tileRowData2 >> colourBit) & 0x1) << 1 | ((tileRowData1 >> colourBit) & 0x1);

 		// Apply the BGP register for palette mapping
-		uint8_t palette = (*BGP >> (colourNum * 2)) & 0x3;
+		uint8_t palette = (readOnlyAddressSpace.memoryLayout.BGP >> (colourNum * 2)) & 0x3;
 		if (xPos == 0)
 			palette = 0x3;
 		switch (palette) {
@@ -198,7 +203,6 @@ void GameBoy::SDL2present() {


 	frameTime = SDL_GetTicks() - frameStart;
-	std::cout << SDL_GetTicks() << " " << frameTime << std::endl;

 	if (frameDelay > frameTime) {
 		SDL_Delay(frameDelay - frameTime);
--- a/src/timing.cpp
+++ b/src/timing.cpp
@@ -4,9 +4,7 @@
 void GameBoy::timingHandler() {
 	if (cycles - lastDivUpdate >= DIVIDER_REGISTER_FREQ) {
 		const uint8_t increments = (cycles - lastDivUpdate) / DIVIDER_REGISTER_FREQ;
-
-		(*DIV) += increments;
-
+		addressSpace.memoryLayout.DIV += increments;
 		lastDivUpdate += increments * DIVIDER_REGISTER_FREQ;
 	}
 }