From 5d28f8727a1d8c1fd0d8b572ca8d6b0706b21748 Mon Sep 17 00:00:00 2001
From: "andres.delikat" <andres.delikat@4bbf4f03-6f44-549e-7e59-35d4b0962838>
Date: Mon, 2 Apr 2012 16:58:04 +0000
Subject: [PATCH] Atari - implement UA mapper (untested)

---
 .../Consoles/Atari/2600/Mappers/mUA.cs        | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/BizHawk.Emulation/Consoles/Atari/2600/Mappers/mUA.cs b/BizHawk.Emulation/Consoles/Atari/2600/Mappers/mUA.cs
index f3165195e6..d479b80f85 100644
--- a/BizHawk.Emulation/Consoles/Atari/2600/Mappers/mUA.cs
+++ b/BizHawk.Emulation/Consoles/Atari/2600/Mappers/mUA.cs
@@ -5,8 +5,42 @@ using System.Text;
 
 namespace BizHawk.Emulation.Consoles.Atari._2600
 {
+	/*
+	UA (UA Ltd)
+	-----
+
+	This one was found out later on, lurking on a proto of Pleaides.  It works with 8K of ROM
+	and banks it in 4K at a time.
+
+	Accessing 0220 will select the first bank, and accessing 0240 will select the second.
+	*/
+
 	class mUA : MapperBase 
 	{
+		int toggle = 0;
 
+		public override byte ReadMemory(ushort addr)
+		{
+			Address(addr);
+			if (addr < 0x1000) return base.ReadMemory(addr);
+			return core.rom[toggle * 4 * 1024 + (addr & 0xFFF)];
+		}
+		public override void WriteMemory(ushort addr, byte value)
+		{
+			Address(addr);
+			if (addr < 0x1000) base.WriteMemory(addr, value);
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			base.SyncState(ser);
+			ser.Sync("toggle", ref toggle);
+		}
+
+		void Address(ushort addr)
+		{
+			if (addr == 0x0220) toggle = 0;
+			else if (addr == 0x0240) toggle = 1;
+		}
 	}
 }