AxibugEmuOnline/AxibugEmuOnline.Client/Assets/MyNes.Core/Eprom.cs

using System;
using System.IO;

namespace MyNes.Core
{
    internal class Eprom
    {
    	private enum EpromDevice
    	{
    		X24C01,
    		X24C02
    	}

    	private enum EpromMode
    	{
    		Data,
    		Addressing,
    		Idle,
    		Read,
    		Write,
    		Ack,
    		NotAck,
    		AckWait
    	}

    	private byte[] data;

    	private EpromMode mode = EpromMode.Data;

    	private EpromMode nextmode = EpromMode.Data;

    	private EpromDevice device = EpromDevice.X24C01;

    	private bool psda;

    	private bool pscl;

    	private int output = 0;

    	private int cbit = 0;

    	private int caddress = 0;

    	private int cdata = 0;

    	private bool isRead;

    	private bool cSCL;

    	private bool cSDA;

    	public Eprom(int memorySize)
    	{
    		Console.WriteLine("Initializing Eprom ...");
    		data = new byte[memorySize];
    		device = ((memorySize == 256) ? EpromDevice.X24C02 : EpromDevice.X24C01);
    		Console.WriteLine("Eprom memory size = " + memorySize);
    		Console.WriteLine("Eprom device = " + device);
    	}

    	public void HardReset()
    	{
    		pscl = false;
    		psda = false;
    		mode = EpromMode.Idle;
    		nextmode = EpromMode.Idle;
    		cbit = 0;
    		caddress = 0;
    		cdata = 0;
    		isRead = false;
    		output = 16;
    	}

    	public void Write(int address, byte data)
    	{
    		cSCL = (data & 0x20) == 32;
    		cSDA = (data & 0x40) == 64;
    		if (pscl && (!cSDA & psda))
    		{
    			Start();
    		}
    		else if (pscl && (cSDA & !psda))
    		{
    			Stop();
    		}
    		else if (cSCL & !pscl)
    		{
    			switch (device)
    			{
    			case EpromDevice.X24C01:
    				RiseX24C01((data >> 6) & 1);
    				break;
    			case EpromDevice.X24C02:
    				RiseX24C02((data >> 6) & 1);
    				break;
    			}
    		}
    		else if (!cSCL & pscl)
    		{
    			switch (device)
    			{
    			case EpromDevice.X24C01:
    				FallX24C01();
    				break;
    			case EpromDevice.X24C02:
    				FallX24C02();
    				break;
    			}
    		}
    		pscl = cSCL;
    		psda = cSDA;
    	}

    	public byte Read(int address)
    	{
    		return (byte)output;
    	}

    	private void Start()
    	{
    		switch (device)
    		{
    		case EpromDevice.X24C01:
    			mode = EpromMode.Addressing;
    			cbit = 0;
    			caddress = 0;
    			output = 16;
    			break;
    		case EpromDevice.X24C02:
    			mode = EpromMode.Data;
    			cbit = 0;
    			output = 16;
    			break;
    		}
    	}

    	private void Stop()
    	{
    		mode = EpromMode.Idle;
    		output = 16;
    	}

    	private void RiseX24C01(int bit)
    	{
    		switch (mode)
    		{
    		case EpromMode.Addressing:
    			if (cbit < 7)
    			{
    				caddress &= ~(1 << cbit);
    				caddress |= bit << cbit++;
    			}
    			else if (cbit < 8)
    			{
    				cbit = 8;
    				if (bit != 0)
    				{
    					nextmode = EpromMode.Read;
    					cdata = data[caddress];
    				}
    				else
    				{
    					nextmode = EpromMode.Write;
    				}
    			}
    			break;
    		case EpromMode.Ack:
    			output = 0;
    			break;
    		case EpromMode.Read:
    			if (cbit < 8)
    			{
    				output = (((cdata & (1 << cbit++)) != 0) ? 16 : 0);
    			}
    			break;
    		case EpromMode.Write:
    			if (cbit < 8)
    			{
    				cdata &= ~(1 << cbit);
    				cdata |= bit << cbit++;
    			}
    			break;
    		case EpromMode.AckWait:
    			if (bit == 0)
    			{
    				nextmode = EpromMode.Idle;
    			}
    			break;
    		case EpromMode.Idle:
    		case EpromMode.NotAck:
    			break;
    		}
    	}

    	private void RiseX24C02(int bit)
    	{
    		switch (mode)
    		{
    		case EpromMode.Data:
    			if (cbit < 8)
    			{
    				cdata &= ~(1 << 7 - cbit);
    				cdata |= bit << 7 - cbit++;
    			}
    			break;
    		case EpromMode.Addressing:
    			if (cbit < 8)
    			{
    				caddress &= ~(1 << 7 - cbit);
    				caddress |= bit << 7 - cbit++;
    			}
    			break;
    		case EpromMode.Read:
    			if (cbit < 8)
    			{
    				output = (((cdata & (1 << 7 - cbit++)) != 0) ? 16 : 0);
    			}
    			break;
    		case EpromMode.Write:
    			if (cbit < 8)
    			{
    				cdata &= ~(1 << 7 - cbit);
    				cdata |= bit << 7 - cbit++;
    			}
    			break;
    		case EpromMode.NotAck:
    			output = 16;
    			break;
    		case EpromMode.Ack:
    			output = 0;
    			break;
    		case EpromMode.AckWait:
    			if (bit == 0)
    			{
    				nextmode = EpromMode.Read;
    				cdata = data[caddress];
    			}
    			break;
    		case EpromMode.Idle:
    			break;
    		}
    	}

    	private void FallX24C01()
    	{
    		switch (mode)
    		{
    		case EpromMode.Addressing:
    			if (cbit == 8)
    			{
    				mode = EpromMode.Ack;
    				output = 16;
    			}
    			break;
    		case EpromMode.Ack:
    			mode = nextmode;
    			cbit = 0;
    			output = 16;
    			break;
    		case EpromMode.Read:
    			if (cbit == 8)
    			{
    				mode = EpromMode.AckWait;
    				caddress = (caddress + 1) & 0x7F;
    			}
    			break;
    		case EpromMode.Write:
    			if (cbit == 8)
    			{
    				mode = EpromMode.Ack;
    				nextmode = EpromMode.Idle;
    				data[caddress] = (byte)cdata;
    				caddress = (caddress + 1) & 0x7F;
    			}
    			break;
    		case EpromMode.Idle:
    			break;
    		}
    	}

    	private void FallX24C02()
    	{
    		switch (mode)
    		{
    		case EpromMode.Data:
    			if (cbit != 8)
    			{
    				break;
    			}
    			if ((cdata & 0xA0) == 160)
    			{
    				cbit = 0;
    				mode = EpromMode.Ack;
    				isRead = (cdata & 1) == 1;
    				output = 16;
    				if (isRead)
    				{
    					nextmode = EpromMode.Read;
    					cdata = data[caddress];
    				}
    				else
    				{
    					nextmode = EpromMode.Addressing;
    				}
    			}
    			else
    			{
    				mode = EpromMode.NotAck;
    				nextmode = EpromMode.Idle;
    				output = 16;
    			}
    			break;
    		case EpromMode.Addressing:
    			if (cbit == 8)
    			{
    				cbit = 0;
    				mode = EpromMode.Ack;
    				nextmode = (isRead ? EpromMode.Idle : EpromMode.Write);
    				output = 16;
    			}
    			break;
    		case EpromMode.Read:
    			if (cbit == 8)
    			{
    				mode = EpromMode.AckWait;
    				caddress = (caddress + 1) & 0xFF;
    			}
    			break;
    		case EpromMode.Write:
    			if (cbit == 8)
    			{
    				cbit = 0;
    				mode = EpromMode.Ack;
    				nextmode = EpromMode.Write;
    				data[caddress] = (byte)cdata;
    				caddress = (caddress + 1) & 0xFF;
    			}
    			break;
    		case EpromMode.NotAck:
    			mode = EpromMode.Idle;
    			cbit = 0;
    			output = 16;
    			break;
    		case EpromMode.Ack:
    		case EpromMode.AckWait:
    			mode = nextmode;
    			cbit = 0;
    			output = 16;
    			break;
    		case EpromMode.Idle:
    			break;
    		}
    	}

    	public void SaveState(BinaryWriter stream)
    	{
    		stream.Write(data);
    		stream.Write((int)mode);
    		stream.Write((int)nextmode);
    		stream.Write(psda);
    		stream.Write(pscl);
    		stream.Write(output);
    		stream.Write(cbit);
    		stream.Write(caddress);
    		stream.Write(cdata);
    		stream.Write(isRead);
    	}

    	public void LoadState(BinaryReader stream)
    	{
    		stream.Read(data, 0, data.Length);
    		mode = (EpromMode)stream.ReadInt32();
    		nextmode = (EpromMode)stream.ReadInt32();
    		psda = stream.ReadBoolean();
    		pscl = stream.ReadBoolean();
    		output = stream.ReadInt32();
    		cbit = stream.ReadInt32();
    		caddress = stream.ReadInt32();
    		cdata = stream.ReadInt32();
    		isRead = stream.ReadBoolean();
    	}
    }
}