Added Master System Memory Bus

Core/Core.csproj

@@ -9,9 +9,7 @@
   <ItemGroup>
     <Folder Include="Audio\" />
     <Folder Include="Cpu\" />
-    <Folder Include="Interfaces\" />
     <Folder Include="Io\" />
-    <Folder Include="Memory\" />
   </ItemGroup>
 
 </Project>

Core/Interfaces/IAudioDevice.cs

@@ -0,0 +1,8 @@
+namespace Core.Interfaces
+{
+    public interface IAudioDevice
+    {
+        // Now accepts the Beeper state + 3 AY frequencies + 3 AY volumes
+        void AddSample(bool isHigh, float freqA, float volA, float freqB, float volB, float freqC, float volC);
+    }
+}

Core/Interfaces/IIoBus.cs

@@ -0,0 +1,8 @@
+namespace Core.Interfaces
+{
+    public interface IIoBus
+    {
+        byte Read(ushort port);
+        void Write(ushort port, byte value);
+    }
+}

Core/Interfaces/IMemory.cs

@@ -0,0 +1,9 @@
+namespace Core.Interfaces
+{
+    public interface IMemory
+    {
+        byte Read(ushort address);
+        void Write(ushort address, byte value);
+        void CleanRAMData();
+    }
+}

Core/Memory/SmsMemoryBus.cs

@@ -0,0 +1,109 @@
+using Core.Interfaces;
+using System;
+
+namespace Core.Memory
+{
+    public class SmsMemoryBus : IMemory
+    {
+        // SMS has 8KB of internal Work RAM
+        private readonly byte[] _workRam = new byte[0x2000];
+
+        // The entire game cartridge loaded into one big array
+        private byte[] _cartridgeRom = Array.Empty<byte>();
+
+        // The Paging Registers (Which 16KB chunk is in which slot?)
+        // Default startup state: Bank 0, 1, and 2 in order.
+        private int _romBank0 = 0;
+        private int _romBank1 = 1;
+        private int _romBank2 = 2;
+
+        // A flag to handle cartridges that don't use paging (like early 32KB games)
+        private bool _isCartridgeLoaded = false;
+
+        public void LoadCartridge(byte[] romData)
+        {
+            _cartridgeRom = romData;
+            _isCartridgeLoaded = true;
+
+            // Reset the mapper on boot
+            _romBank0 = 0;
+            _romBank1 = 1;
+            _romBank2 = 2;
+
+            // Clean the RAM
+            CleanRAMData();
+        }
+
+        public byte Read(ushort address)
+        {
+            if (address < 0x4000) // ROM Slot 0 (0x0000 - 0x3FFF)
+            {
+                // SMS Hardware Quirk: The first 1KB (0x0000 - 0x03FF) is NEVER paged. 
+                // It is hardwired to Bank 0 so the interrupt handlers don't crash.
+                if (address < 0x0400) return ReadFromCartridge(0, address);
+
+                return ReadFromCartridge(_romBank0, address);
+            }
+            if (address < 0x8000) // ROM Slot 1 (0x4000 - 0x7FFF)
+            {
+                return ReadFromCartridge(_romBank1, address & 0x3FFF);
+            }
+            if (address < 0xC000) // ROM Slot 2 (0x8000 - 0xBFFF)
+            {
+                return ReadFromCartridge(_romBank2, address & 0x3FFF);
+            }
+
+            // If we are here, we are in System RAM (0xC000 - 0xFFFF)
+            // The & 0x1FFF handles the 8KB mirroring automatically!
+            return _workRam[address & 0x1FFF];
+        }
+
+        public void Write(ushort address, byte value)
+        {
+            if (address < 0xC000)
+            {
+                // You cannot write to a ROM cartridge!
+                return;
+            }
+
+            // Write to System RAM
+            _workRam[address & 0x1FFF] = value;
+
+            // --- THE SEGA MAPPER ---
+            // If the CPU wrote to the very top of memory, it is commanding a bank swap!
+            if (address == 0xFFFD)
+            {
+                _romBank0 = value;
+            }
+            else if (address == 0xFFFE)
+            {
+                _romBank1 = value;
+            }
+            else if (address == 0xFFFF)
+            {
+                _romBank2 = value;
+            }
+        }
+
+        private byte ReadFromCartridge(int bankIndex, int offset)
+        {
+            if (!_isCartridgeLoaded) return 0xFF; // Floating bus if no game
+
+            int absoluteAddress = (bankIndex * 0x4000) + offset;
+
+            // Safety check in case a game asks for a bank outside its file size
+            if (absoluteAddress >= _cartridgeRom.Length)
+            {
+                // Wrap around (mirrors the ROM if it's smaller than the requested bank)
+                absoluteAddress %= _cartridgeRom.Length;
+            }
+
+            return _cartridgeRom[absoluteAddress];
+        }
+
+        public void CleanRAMData()
+        {
+            Array.Clear(_workRam, 0, _workRam.Length);
+        }
+    }
+}