AxibugEmuOnline/OtherCore/MyNes.Standard2/MyNes.Core/Eprom.cs

384 lines
7.4 KiB
C#

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;
private EpromMode nextmode;
private EpromDevice device;
private bool psda;
private bool pscl;
private int output;
private int cbit;
private int caddress;
private int cdata;
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();
}
}
}