Atari 2600 - implement mapper FE

BizHawk.Emulation.Cores/Consoles/Atari/2600/Atari2600.Core.cs

@@ -68,8 +68,8 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 		public byte ReadMemory(ushort addr)
 		{
+			_mapper.Bit13 = addr.Bit(13);
 			var temp = _mapper.ReadMemory((ushort)(addr & 0x1FFF));
-
 			CoreComm.MemoryCallbackSystem.CallRead(addr);
 
 			return temp;

BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/MapperBase.cs

@@ -39,5 +39,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 		public virtual void HardReset() { }
 
+		// THis is here purely for mapper 3E because it needs the 13th bit to determine bankswitching (but only receives the first 12 on read memory)
+		public bool Bit13 { get; set; }
 	}
 }

BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mFE.cs

@@ -1,4 +1,4 @@
-using System;
+using BizHawk.Common;
 
 namespace BizHawk.Emulation.Cores.Atari.Atari2600
 {
@@ -56,12 +56,16 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 	Using emulators or similar there is a large cheat that can be used.  A13 can be used
 	to simply select which 8K bank to be in.
 	*/
-	
 	internal class mFE : MapperBase 
 	{
-		public mFE()
+		public override byte ReadMemory(ushort addr)
 		{
-			throw new NotImplementedException();
+			if (addr < 0x1000)
+			{
+				return base.ReadMemory(addr);
+			}
+
+			return Core.Rom[(addr & 0x0FFF) + (Bit13 ? 0 : 4096)];
 		}
 	}
 }