BizHawk/BizHawk.Emulation/Computers/Commodore64/MOS/MOS6510.cs

using BizHawk.Emulation.CPUs.M6502;
using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

using BizHawk.Common;

namespace BizHawk.Emulation.Computers.Commodore64.MOS
{
	// an extension of the 6502 processor

	sealed public class MOS6510
	{
		// ------------------------------------

		MOS6502X cpu;
		bool pinNMILast;
		LatchedPort port;
		bool thisNMI;

		public Func<int, byte> PeekMemory;
		public Action<int, byte> PokeMemory;
		public Func<bool> ReadAEC;
		public Func<bool> ReadIRQ;
		public Func<bool> ReadNMI;
		public Func<bool> ReadRDY;
		public Func<int, byte> ReadMemory;
		public Func<byte> ReadPort;
		public Action<int, byte> WriteMemory;

		// ------------------------------------

		public MOS6510()
		{
			cpu = new MOS6502X();

			// configure cpu r/w
			cpu.DummyReadMemory = Read;
			cpu.ReadMemory = Read;
			cpu.WriteMemory = Write;

			// perform hard reset
			HardReset();
		}

		public void HardReset()
		{
			// configure CPU defaults
			cpu.Reset();
			cpu.FlagI = true;
			cpu.BCD_Enabled = true;
			if (ReadMemory != null)
				cpu.PC = (ushort)(ReadMemory(0x0FFFC) | (ReadMemory(0x0FFFD) << 8));

			// configure data port defaults
			port = new LatchedPort();
			port.Direction = 0x00;
			port.Latch = 0xFF;

			// NMI is high on startup (todo: verify)
			pinNMILast = true;
		}

		// ------------------------------------

		public void ExecutePhase1()
		{
			cpu.IRQ = !ReadIRQ();
		}

		public void ExecutePhase2()
		{
			cpu.RDY = ReadRDY();

			// the 6502 core expects active high
			// so we reverse the polarity here
			thisNMI = ReadNMI();
			if (!thisNMI && pinNMILast)
				cpu.NMI = true;

			if (ReadAEC())
			{
				cpu.ExecuteOne();
				pinNMILast = thisNMI;
			}
		}

		// ------------------------------------

		public ushort PC
		{
			get
			{
				return cpu.PC;
			}
			set
			{
				cpu.PC = value;
			}
		}

		public byte Peek(int addr)
		{
			if (addr == 0x0000)
				return port.Direction;
			else if (addr == 0x0001)
				return PortData;
			else
				return PeekMemory(addr);
		}

		public void Poke(int addr, byte val)
		{
			if (addr == 0x0000)
				port.Direction = val;
			else if (addr == 0x0001)
				port.Latch = val;
			else
				PokeMemory(addr, val);
		}

		public byte PortData
		{
			get
			{
				return port.ReadInput(ReadPort());
			}
			set
			{
				port.Latch = value;
			}
		}

		public byte Read(ushort addr)
		{
			if (addr == 0x0000)
				return port.Direction;
			else if (addr == 0x0001)
				return PortData;
			else
				return ReadMemory(addr);
		}

		public void SyncState(Serializer ser)
		{
			cpu.SyncState(ser);
			SaveState.SyncObject(ser, this);
		}

		public void Write(ushort addr, byte val)
		{
			if (addr == 0x0000)
				port.Direction = val;
			else if (addr == 0x0001)
				port.Latch = val;
			WriteMemory(addr, val);
		}
	}
}