From 3d1e6ca83004fd576da3a18e6136f8d22c521bc5 Mon Sep 17 00:00:00 2001
From: adelikat <adelikat@tasvideos.org>
Date: Fri, 4 Apr 2014 23:49:03 +0000
Subject: [PATCH] Atari 2600 - implement mapper F6SC, and slight fix to F8SC
 (uncomment read of write port emulation)

---
 .../Consoles/Atari/2600/Mappers/mF6SC.cs      | 72 +++++++++++++++++--
 .../Consoles/Atari/2600/Mappers/mF8SC.cs      | 13 ++--
 2 files changed, 73 insertions(+), 12 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF6SC.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF6SC.cs
index de61e9a55f..010c9130dd 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF6SC.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF6SC.cs
@@ -1,16 +1,78 @@
-using System;
+using BizHawk.Common;
 
 namespace BizHawk.Emulation.Cores.Atari.Atari2600
 {
 	/**
-	Cartridge class used for Atari's 32K bankswitched games with
-	128 bytes of RAM.  There are eight 4K banks.
+	Cartridge class used for Atari's 16K bankswitched games with
+	128 bytes of RAM.  There are four 4K banks.
 	*/
 	internal class mF6SC : MapperBase
 	{
-		public mF6SC()
+		private int _bank4k;
+		private ByteBuffer _ram = new ByteBuffer(128);
+
+		private byte ReadMem(ushort addr, bool peek)
 		{
-			throw new NotImplementedException();
+			if (!peek)
+			{
+				Address(addr);
+			}
+
+			if (addr < 0x1000)
+			{
+				return base.ReadMemory(addr);
+			}
+
+			if (addr < 0x1080)
+			{
+				_ram[(addr & 0x7F)] = 0xFF; // Reading from the write port triggers an unwanted write of open bus
+				return 0xFF; // 0xFF is used for deterministic emulation, in reality it would be a random value based on pins being high or low
+			}
+			else if (addr < 0x1100)
+			{
+				return _ram[(addr & 0x7F)];
+			}
+
+			return core.rom[(_bank4k << 12) + (addr & 0xFFF)];
+		}
+
+		public override byte ReadMemory(ushort addr)
+		{
+			return ReadMem(addr, false);
+		}
+
+		public override byte PeekMemory(ushort addr)
+		{
+			return ReadMem(addr, true);
+		}
+
+		public override void WriteMemory(ushort addr, byte value)
+		{
+			Address(addr);
+
+			if (addr < 0x1000)
+			{
+				base.WriteMemory(addr, value);
+			}
+			else if ((addr & 0x0FFF) < 0x80)
+			{
+				_ram[addr & 0x7F] = value;
+			}
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("bank_4k", ref _bank4k);
+			ser.Sync("auxRam", ref _ram);
+		}
+
+		private void Address(ushort addr)
+		{
+			if (addr == 0x1FF6) _bank4k = 0;
+			if (addr == 0x1FF7) _bank4k = 1;
+			if (addr == 0x1FF8) _bank4k = 2;
+			if (addr == 0x1FF9) _bank4k = 3;
 		}
 	}
 }
\ No newline at end of file
diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF8SC.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF8SC.cs
index 517dfd6820..81bbec6be7 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF8SC.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mF8SC.cs
@@ -23,13 +23,12 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				return base.ReadMemory(addr);
 			}
 
-			//if (addr < 0x1080)
-			//{
-			//	_ram[(addr & 0x7F)] = 0xFF; // Reading from the write port triggers an unwanted write of open bus
-			//	return 0xFF; // 0xFF is used for deterministic emulation, in reality it would be a random value based on pins being high or low
-			//}
-			//else 
-				if (addr < 0x1100)
+			if (addr < 0x1080)
+			{
+				_ram[(addr & 0x7F)] = 0xFF; // Reading from the write port triggers an unwanted write of open bus
+				return 0xFF; // 0xFF is used for deterministic emulation, in reality it would be a random value based on pins being high or low
+			}
+			else if (addr < 0x1100)
 			{
 				return _ram[(addr & 0x7F)];
 			}