Added AY38912 support

Core/Cpu/Z80.cs

@@ -547,7 +547,7 @@ namespace Core.Cpu
             return (ushort)((high << 8) | low);
         }
 
-        private int ExecuteOpcode(byte opcode)
+        internal int ExecuteOpcode(byte opcode)
         {
             sbyte offset = 0;
             byte oldCarry = 0;
@@ -1588,6 +1588,32 @@ namespace Core.Cpu
                         AF.Low = flags;
                         return 16;
                     }
+                case 0xAB: // OUTD
+                    {
+                        // 1. Read the byte from memory at the HL address (Applying Wait States!)
+                        byte outdVal = ReadMemory(HL.Word);
+
+                        // 2. Decrement the B register
+                        BC.High--;
+
+                        // 3. Output that byte to the hardware port stored in BC
+                        _simpleIoBus.WritePort(BC.Word, outdVal);
+
+                        // 4. Decrement HL
+                        HL.Word--;
+
+                        // 5. Update Flags
+                        // The N flag (Bit 1) is always set.
+                        AF.Low |= 0x02;
+
+                        // The Z flag (Bit 6) is set if B reaches 0, otherwise cleared.
+                        if (BC.High == 0)
+                            AF.Low |= 0x40;
+                        else
+                            AF.Low &= 0xBF;
+
+                        return 16; // Takes 16 T-States
+                    }
                 case 0xB9: // CPDR
                     {
                         byte memVal = ReadMemory(HL.Word);