Added Golden Axe Warrior. Added Debugger.

Core/Core.csproj

@@ -9,7 +9,6 @@
   <ItemGroup>
     <Folder Include="Audio\" />
     <Folder Include="Cpu\" />
-    <Folder Include="Io\" />
   </ItemGroup>
 
 </Project>

Core/Cpu/Z80.cs

@@ -53,12 +53,12 @@ namespace Core.Cpu
 
         // The Memory Bus
         private readonly IMemory _memory;
-        private readonly IO_Bus _simpleIoBus;
+        private readonly IIoBus _simpleIoBus;
 
         //External Timing interface
         public Func<ushort, long, int>? WaitStateCallback { get; set; }
 
-        public Z80(IMemory memory, IO_Bus ioBus)
+        public Z80(IMemory memory, IIoBus ioBus)
         {
             _memory = memory;
             _simpleIoBus = ioBus;

Core/Interfaces/IIoBus.cs

@@ -2,7 +2,7 @@
 {
     public interface IIoBus
     {
-        byte Read(ushort port);
-        void Write(ushort port, byte value);
+        byte ReadPort(ushort port);
+        void WritePort(ushort port, byte value);
     }
 }

Core/Io/SmsIoBus.cs

@@ -0,0 +1,62 @@
+using Core.Interfaces;
+
+namespace Core.Io
+{
+    public class SmsIoBus : IIoBus
+    {
+        // We will wire these up in the next phases!
+        // public Vdp VideoProcessor { get; set; }
+        // public Psg AudioProcessor { get; set; }
+
+        // Joypad State (0xFF means no buttons pressed - the SMS uses Active-Low logic!)
+        public byte Joypad1State { get; set; } = 0xFF;
+        public byte Joypad2State { get; set; } = 0xFF;
+
+        public byte ReadPort(ushort port)
+        {
+            // The Z80 can output 16-bit port addresses, but the Master System 
+            // hardware only physically wires up the bottom 8 bits.
+            byte lowerPort = (byte)(port & 0xFF);
+
+            if (lowerPort >= 0x80 && lowerPort <= 0xBF)
+            {
+                // VDP Read (Usually 0xBE for VRAM Data, 0xBF for Status Flags)
+                // return VideoProcessor.ReadPort(lowerPort);
+                return 0x00;
+            }
+            if (lowerPort == 0xDC)
+            {
+                // Port 0xDC: Player 1 (Up, Down, Left, Right, 1, 2) + Player 2 (Up, Down)
+                return Joypad1State;
+            }
+            if (lowerPort == 0xDD)
+            {
+                // Port 0xDD: Player 2 (Left, Right, 1, 2) + Reset Button
+                return Joypad2State;
+            }
+
+            return 0xFF; // Floating bus
+        }
+
+        public void WritePort(ushort port, byte value)
+        {
+            byte lowerPort = (byte)(port & 0xFF);
+
+            if (lowerPort >= 0x40 && lowerPort <= 0x7F)
+            {
+                // PSG Audio Write (Usually written exactly to 0x7F)
+                // AudioProcessor.WriteData(value);
+            }
+            else if (lowerPort >= 0x80 && lowerPort <= 0xBF)
+            {
+                // VDP Write (Usually 0xBE for VRAM Data, 0xBF for Control Registers)
+                // VideoProcessor.WritePort(lowerPort, value);
+            }
+            else if (lowerPort <= 0x3F)
+            {
+                // Port 0x3E is used by the BIOS to enable/disable the cartridge slot
+                // We can usually ignore this if we are just directly booting game ROMs!
+            }
+        }
+    }
+}

Core/SmsMachine.cs

@@ -0,0 +1,61 @@
+using Core.Cpu;
+using Core.Io;
+using Core.Memory;
+
+namespace Core
+{
+    public class SmsMachine
+    {
+        public Z80 Cpu { get; private set; }
+        public SmsMemoryBus MemoryBus { get; private set; }
+        public SmsIoBus IoBus { get; private set; }
+        public ushort? Breakpoint { get; set; } = null;
+
+        // NTSC SMS T-States per frame
+        public const int TStatesPerFrame = 59736;
+        public long TotalFrameCount { get; private set; } = 0;
+        public double FramesPerSecond { get; private set; } = 0;
+        public double FrameTime { get; private set; } = 0;
+
+        public SmsMachine()
+        {
+            MemoryBus = new SmsMemoryBus();
+            IoBus = new SmsIoBus();
+            Cpu = new Z80(MemoryBus, IoBus);
+        }
+
+        public void LoadCartridge(byte[] romData)
+        {
+            MemoryBus.LoadCartridge(romData);
+            Reset();
+        }
+
+        public void Reset()
+        {
+            MemoryBus.CleanRAMData();
+            Cpu.Reset();
+
+            // We will reset the VDP and PSG here later!
+        }
+
+        public void RunFrame()
+        {
+            long currentFrameTStates = 0;
+
+            while (currentFrameTStates < TStatesPerFrame)
+            {
+                int tStates = Cpu.Step();
+                currentFrameTStates += tStates;
+
+                // --- FUTURE EXPANSION ---
+                // VideoProcessor.Update(tStates);
+                // AudioProcessor.Update(tStates);
+
+                // if (VideoProcessor.IsVBlanking && VideoProcessor.InterruptsEnabled)
+                // {
+                //     Cpu.RequestInterrupt();
+                // }
+            }
+        }
+    }
+}