Gameboy/MMU.c at master · sacert/Gameboy · GitHub

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#include <string.h>
#include "rom.h"
#include "MMU.h"
#include "interrupt.h"
#include "lcd.h"
#include "timer.h"
#include "sdl.h"

int joypadButtons;
int joypadDirections;

void copyToOAM(unsigned short OAM, unsigned short DMA, size_t length) {
	unsigned int i;
	for(i = 0; i < length; i++)
        writeByte(OAM + i, readByte(DMA + i));
}

unsigned char readByte(unsigned short address) {

    unsigned char mask = 0;

    if (0x0000 <= address && address <= 0x7FFF)
        return cart[address];
    else if (0x8000 <= address && address <= 0x9FFF)
        return vram[address - 0x8000];
    else if (0xA000 <= address && address <= 0xBFFF)
        return sram[address - 0xA000];
    else if (0xC000 <= address && address <= 0xDFFF)
        return wram[address - 0xC000];
    else if (0xE000 <= address && address <= 0xFDFF) // echo of wram
        return wram[address - 0xE000];
    else if (0xFE00 <= address && address <= 0xFEFF)
        return oam[address - 0xFE00];
    else if (address == 0xFF00) {
        if (!joypadButtons)
            mask = getButton();
        if (!joypadDirections)
            mask = getDirection();
        return (0xC0 | (0xF ^ mask) | ((joypadButtons) | (joypadDirections)));
    }
    else if (address == 0xFF04)
        return getDiv();
    else if (address == 0xFF05)
        return getTima();
    else if (address == 0xFF06)
        return getTma();
    else if (address == 0xFF04)
        return getTac();
    else if (address == 0xFF0F)
        return interrupt.flags;
    else if (address == 0xFF40)
        return getLCDC();
    else if (address == 0xFF41)
        return getLCDS();
    else if (address == 0xFF42)
        return getScrollY();
    else if (address == 0xFF43)
        return getScrollX();
    else if (address == 0xFF44)
        return getLine();
    else if(0xFF00 <= address && address <= 0xFF7F) // maybe only up to 0xFF4F
    	return io[address - 0xFF00];
    else if (0xFF80 <= address && address <= 0xFFFE)
        return hram[address - 0xFF80];
    else if (address == 0xFFFF)
        return interrupt.enable;

    return 0;
}

unsigned short readShort(unsigned short address) {
    return (readByte(address) | (readByte(address+1) << 8));
}

void writeByte(unsigned short address, unsigned char value) {

    // cant write to ROM
    if (0x8000 <= address && address <= 0x9FFF)
        vram[address - 0x8000] = value;
    else if (0xA000 <= address && address <= 0xBFFF)
        sram[address - 0xA000] = value;
    else if (0xC000 <= address && address <= 0xDFFF)
        wram[address - 0xC000] = value;
    else if (0xE000 <= address && address <= 0xFDFF)
        wram[address - 0xE000] = value;
    else if (0xFE00 <= address && address <= 0xFEFF)
        oam[address - 0xFE00] = value;
    else if (address == 0xFF04)
        setDiv(value);
    else if (address == 0xFF05)
        setTima(value);
    else if (address == 0xFF06)
        setTma(value);
    else if (address == 0xFF04)
        setTac(value);
    else if (address == 0xFF40)
        setLCDC(value);
    else if (address == 0xFF41)
        setLCDS(value);
    else if (address == 0xFF42)
        setScrollY(value);
    else if (address == 0xFF43)
        setScrollX(value);
    else if (address == 0xFF45)
        setLyCompare(value);
    else if(address == 0xff46)
        copyToOAM(0xfe00, value << 8, 160); // OAM DMA
    else if (address == 0xFF47)
        setBGPalette(value);
    else if (address == 0xFF48)
        setSpritePalette1(value);
    else if (address == 0xFF49)
        setSpritePalette2(value);
    else if (address == 0xFF4A)
        setWindowY(value);
    else if (address == 0xFF4B)
        setWindowX(value);
    else if (address == 0xFF00) {
        joypadDirections = value & 0x10;
        joypadButtons = value & 0x20;
    }
    else if(0xFF00 <= address && address <= 0xFF7F)
    	io[address - 0xFF00] = value;
    else if (0xFF80 <= address && address <= 0xFFFE)
        hram[address - 0xFF80] = value;
    else if (address == 0xFF0F)
        interrupt.flags = value;
    else if (address == 0xFFFF)
        interrupt.enable = value;

}

void writeShort(unsigned short address, unsigned short value) {
    writeByte(address,(value & 0x00FF));
    writeByte(address+1,(value & 0xFF00) >> 8);
}

void changeMemoryBank(int bankNum) {
    memcpy(&cart[0x4000],&rom.romBytes[bankNum * 0x4000],0x4000);
}

void memInit(void) {
    writeByte(0xFF10, 0x80);
    writeByte(0xFF11, 0xBF);
    writeByte(0xFF12, 0xF3);
    writeByte(0xFF14, 0xBF);
    writeByte(0xFF16, 0x3F);
    writeByte(0xFF19, 0xBF);
    writeByte(0xFF1A, 0x7F);
    writeByte(0xFF1B, 0xFF);
    writeByte(0xFF1C, 0x9F);
    writeByte(0xFF1E, 0xBF);
    writeByte(0xFF20, 0xFF);
    writeByte(0xFF23, 0xBF);
    writeByte(0xFF24, 0x77);
    writeByte(0xFF25, 0xF3);
    writeByte(0xFF26, 0xF1);
    writeByte(0xFF40, 0x91);
    writeByte(0xFF47, 0xFC);
    writeByte(0xFF48, 0xFF);
    writeByte(0xFF49, 0xFF);
}