Genesis.IO.cs

using BizHawk.Common;

namespace BizHawk.Emulation.Cores.Sega.Genesis
{
	partial class Genesis
	{
		bool SegaCD = false;

		class IOPort
		{
			public byte Data;
			public byte Control;
			public byte TxData;
			public byte RxData;
			public byte SCtrl;
			// TODO- a reference to connected device? That gets into the issue of configuring different types of controllers. :|

			public bool TH { get { return (Data & 0x40) != 0; } }
		}

		IOPort[] IOPorts = new IOPort[] 
		{ 
			new IOPort { Data = 0x7F, TxData = 0xFF, RxData = 0xFF, SCtrl = 0xFF }, 
			new IOPort { Data = 0x7F, TxData = 0xFF, RxData = 0xFF, SCtrl = 0xFF }, 
			new IOPort { Data = 0x7F, TxData = 0xFF, RxData = 0xFF, SCtrl = 0xFF } 
		};

		byte ReadIO(int offset)
		{
			offset >>= 1;
			offset &= 0x0F;
			if (offset > 1)
				Log.Note("CPU", "^^^ IO Read {0}: 00", offset);
			switch (offset)
			{
				case 0: // version
					byte value = (byte)(SegaCD ? 0x00 : 0x20);
					switch ((char)RomData[0x01F0])
					{
						case 'J': value |= 0x00; break;
						case 'U': value |= 0x80; break;
						case 'E': value |= 0xC0; break;
						case 'A': value |= 0xC0; break;
						case '4': value |= 0x80; break;
						default: value |= 0x80; break;
					}
					//value |= 1; // US
					Log.Note("CPU", "^^^ IO Read 0: {0:X2}", value);
					return value;
				case 1: // Port A 
					lagged = false;
					ReadController(ref IOPorts[0].Data);
					Log.Note("CPU", "^^^ IO Read 1: {0:X2}", IOPorts[0].Data);
					return IOPorts[0].Data;
				case 2: return 0xFF;
				case 3: return 0xFF;

				case 0x04: return IOPorts[0].Control;
				case 0x05: return IOPorts[1].Control;
				case 0x06: return IOPorts[2].Control;

				case 0x07: return IOPorts[0].TxData;
				case 0x08: return IOPorts[0].RxData;
				case 0x09: return IOPorts[0].SCtrl;

				case 0x0A: return IOPorts[1].TxData;
				case 0x0B: return IOPorts[1].RxData;
				case 0x0C: return IOPorts[1].SCtrl;

				case 0x0D: return IOPorts[2].TxData;
				case 0x0E: return IOPorts[2].RxData;
				case 0x0F: return IOPorts[2].SCtrl;
			}
			Log.Note("CPU", "^^^ IO Read {0}: {1:X2}", offset, 0xFF);
			return 0xFF;
		}

		void WriteIO(int offset, int value)
		{
			offset >>= 1;
			offset &= 0x0F;

			switch (offset)
			{
				case 0x00: break;

				case 0x01: IOPorts[0].Data = (byte)value; break;
				case 0x02: IOPorts[1].Data = (byte)value; break;
				case 0x03: IOPorts[2].Data = (byte)value; break;

				case 0x04: IOPorts[0].Control = (byte)value; break;
				case 0x05: IOPorts[1].Control = (byte)value; break;
				case 0x06: IOPorts[2].Control = (byte)value; break;

				case 0x07: IOPorts[0].TxData = (byte)value; break;
				case 0x08: IOPorts[0].RxData = (byte)value; break;
				case 0x09: IOPorts[0].SCtrl = (byte)value; break;

				case 0x0A: IOPorts[1].TxData = (byte)value; break;
				case 0x0B: IOPorts[1].RxData = (byte)value; break;
				case 0x0C: IOPorts[1].SCtrl = (byte)value; break;

				case 0x0D: IOPorts[2].TxData = (byte)value; break;
				case 0x0E: IOPorts[2].RxData = (byte)value; break;
				case 0x0F: IOPorts[2].SCtrl = (byte)value; break;
			}
		}

		void ReadController(ref byte data)
		{
			InputCallbacks.Call();
			data &= 0xC0;
			if ((data & 0x40) != 0) // TH high
			{
				if (Controller.IsPressed("P1 Up") == false) data |= 0x01;
				if (Controller.IsPressed("P1 Down") == false) data |= 0x02;
				if (Controller.IsPressed("P1 Left") == false) data |= 0x04;
				if (Controller.IsPressed("P1 Right") == false) data |= 0x08;
				if (Controller.IsPressed("P1 B") == false) data |= 0x10;
				if (Controller.IsPressed("P1 C") == false) data |= 0x20;
			}
			else
			{ // TH low
				if (Controller.IsPressed("P1 Up") == false) data |= 0x01;
				if (Controller.IsPressed("P1 Down") == false) data |= 0x02;
				if (Controller.IsPressed("P1 A") == false) data |= 0x10;
				if (Controller.IsPressed("P1 Start") == false) data |= 0x20;
			}

		}
	}
}