feat(memory): add MMU memory map and OAM DMA

src/GameBoy.Core/Memory/Mmu.cs

@@ -0,0 +1,142 @@
+using System;
+using System.IO;
+using GameBoy.Audio;
+using GameBoy.Cpu;
+using GameBoy.Input;
+using GameBoy.Serial;
+using GameBoy.Timing;
+using GameBoy.Video;
+
+namespace GameBoy.Memory
+{
+    public sealed class Mmu
+    {
+        private readonly Cartridge.Cartridge cartridge;
+        private readonly Ppu ppu;
+        private readonly Timer timer;
+        private readonly Joypad joypad;
+        private readonly SerialPort serial;
+        private readonly Apu apu;
+        private readonly InterruptController interrupts;
+
+        private readonly byte[] wram = new byte[0x2000];
+        private readonly byte[] hram = new byte[0x7F];
+
+        public OamDma? Dma;
+
+        public Mmu(
+            Cartridge.Cartridge cartridge,
+            Ppu ppu,
+            Timer timer,
+            Joypad joypad,
+            SerialPort serial,
+            Apu apu,
+            InterruptController interrupts)
+        {
+            this.cartridge = cartridge;
+            this.ppu = ppu;
+            this.timer = timer;
+            this.joypad = joypad;
+            this.serial = serial;
+            this.apu = apu;
+            this.interrupts = interrupts;
+        }
+
+        public byte Read(ushort address)
+        {
+            if (address < 0x8000)
+                return cartridge.Read(address);
+            if (address < 0xA000)
+                return ppu.ReadVram(address);
+            if (address < 0xC000)
+                return cartridge.Read(address);
+            if (address < 0xE000)
+                return wram[address - 0xC000];
+            if (address < 0xFE00)
+                return wram[address - 0xE000];
+            if (address < 0xFEA0)
+                return ppu.ReadOam(address);
+            if (address < 0xFF00)
+                return 0xFF;
+            if (address < 0xFF80)
+                return ReadIo(address);
+            if (address < 0xFFFF)
+                return hram[address - 0xFF80];
+            return interrupts.Enable;
+        }
+
+        public void Write(ushort address, byte value)
+        {
+            if (address < 0x8000)
+                cartridge.Write(address, value);
+            else if (address < 0xA000)
+                ppu.WriteVram(address, value);
+            else if (address < 0xC000)
+                cartridge.Write(address, value);
+            else if (address < 0xE000)
+                wram[address - 0xC000] = value;
+            else if (address < 0xFE00)
+                wram[address - 0xE000] = value;
+            else if (address < 0xFEA0)
+                ppu.WriteOam(address, value);
+            else if (address < 0xFF00)
+            {
+            }
+            else if (address < 0xFF80)
+                WriteIo(address, value);
+            else if (address < 0xFFFF)
+                hram[address - 0xFF80] = value;
+            else
+                interrupts.Enable = value;
+        }
+
+        private byte ReadIo(ushort address)
+        {
+            if (address == 0xFF00)
+                return joypad.Read();
+            if (address == 0xFF01 || address == 0xFF02)
+                return serial.Read(address);
+            if (address >= 0xFF04 && address <= 0xFF07)
+                return timer.Read(address);
+            if (address == 0xFF0F)
+                return interrupts.ReadFlag();
+            if (address >= 0xFF10 && address <= 0xFF3F)
+                return apu.Read(address);
+            if (address == 0xFF46)
+                return Dma!.Page;
+            if (address >= 0xFF40 && address <= 0xFF4B)
+                return ppu.ReadRegister(address);
+            return 0xFF;
+        }
+
+        private void WriteIo(ushort address, byte value)
+        {
+            if (address == 0xFF00)
+                joypad.Write(value);
+            else if (address == 0xFF01 || address == 0xFF02)
+                serial.Write(address, value);
+            else if (address >= 0xFF04 && address <= 0xFF07)
+                timer.Write(address, value);
+            else if (address == 0xFF0F)
+                interrupts.WriteFlag(value);
+            else if (address >= 0xFF10 && address <= 0xFF3F)
+                apu.Write(address, value);
+            else if (address == 0xFF46)
+                Dma!.Start(value);
+            else if (address >= 0xFF40 && address <= 0xFF4B)
+                ppu.WriteRegister(address, value);
+        }
+
+        public void SaveState(BinaryWriter writer)
+        {
+            writer.Write(wram);
+            writer.Write(hram);
+        }
+
+        public void LoadState(BinaryReader reader)
+        {
+            Array.Copy(reader.ReadBytes(wram.Length), wram, wram.Length);
+            Array.Copy(reader.ReadBytes(hram.Length), hram, hram.Length);
+        }
+    }
+}

src/GameBoy.Core/Memory/OamDma.cs

@@ -0,0 +1,64 @@
+using System.IO;
+using GameBoy.Video;
+
+namespace GameBoy.Memory
+{
+    public sealed class OamDma
+    {
+        private readonly Mmu mmu;
+        private readonly Ppu ppu;
+
+        private bool active;
+        private int index;
+        private int subDot;
+
+        public byte Page { get; private set; }
+
+        public OamDma(Mmu mmu, Ppu ppu)
+        {
+            this.mmu = mmu;
+            this.ppu = ppu;
+        }
+
+        public void Start(byte page)
+        {
+            Page = page;
+            active = true;
+            index = 0;
+            subDot = 0;
+        }
+
+        public void Step()
+        {
+            if (!active)
+                return;
+
+            subDot++;
+            if (subDot < 4)
+                return;
+
+            subDot = 0;
+            ushort source = (ushort)((Page << 8) | index);
+            ppu.WriteOamDma(index, mmu.Read(source));
+            index++;
+            if (index == 0xA0)
+                active = false;
+        }
+
+        public void SaveState(BinaryWriter writer)
+        {
+            writer.Write(active);
+            writer.Write(index);
+            writer.Write(subDot);
+            writer.Write(Page);
+        }
+
+        public void LoadState(BinaryReader reader)
+        {
+            active = reader.ReadBoolean();
+            index = reader.ReadInt32();
+            subDot = reader.ReadInt32();
+            Page = reader.ReadByte();
+        }
+    }
+}