From a1cdd5dbfda6572c4f87f08855904959a072b416 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@zeromus.org>
Date: Thu, 5 Apr 2012 18:55:34 +0000
Subject: [PATCH] nes-fix mapper 242

---
 .../Consoles/Nintendo/NES/Boards/Mapper242.cs | 69 +++++++++----------
 1 file changed, 33 insertions(+), 36 deletions(-)

diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper242.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper242.cs
index e529095224..aac792257b 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper242.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Boards/Mapper242.cs
@@ -4,9 +4,7 @@ using System.Diagnostics;
 
 namespace BizHawk.Emulation.Consoles.Nintendo
 {
-	//(doesnt work in neshawk; works in fceux)
-
-    /*
+	/*
 PCB Class: Unknown
 iNES Mapper 242
 PRG-ROM: 32KB
@@ -15,18 +13,18 @@ CHR-ROM: 16KB
 CHR-RAM: None
 Battery is not available
 mirroring - both
-     * 
-     * Games:
-     * Wai Xing Zhan Shi (Ch)
-     */
+	 * 
+	 * Games:
+	 * Wai Xing Zhan Shi (Ch)
+	 */
 
-    class Mapper242 : NES.NESBoardBase
-    {
-        int prg, mirror;
-        
-        public override bool Configure(NES.EDetectionOrigin origin)
-        {
-            //configure
+	class Mapper242 : NES.NESBoardBase
+	{
+		int prg;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			//configure
 			switch (Cart.board_type)
 			{
 				case "MAPPER242":
@@ -34,32 +32,31 @@ mirroring - both
 				default:
 					return false;
 			}
-            return true;
-        }
+			SetMirrorType(NES.NESBoardBase.EMirrorType.Vertical); 
+			return true;
+		}
 
-        public override byte ReadPRG(int addr)
-        {
-            return ROM[addr + (prg * 0x8000)];
-        }
+		public override byte ReadPRG(int addr)
+		{
+			return ROM[addr + (prg * 0x8000)];
+		}
 
-        public override void WritePRG(int addr, byte value)
-        {
-			mirror = (value & 0x03);
+		public override void WritePRG(int addr, byte value)
+		{
 			prg = (addr >> 3) & 15;
-			switch (mirror)
-			{
-				case 0: SetMirrorType(NES.NESBoardBase.EMirrorType.Vertical); break;
-				case 1: SetMirrorType(NES.NESBoardBase.EMirrorType.Horizontal); break;
-				case 2: SetMirrorType(NES.NESBoardBase.EMirrorType.OneScreenA); break;
-				case 3: SetMirrorType(NES.NESBoardBase.EMirrorType.OneScreenB); break;
-			}
-        }
+			//fceux had different logic here for the mirroring, but that didnt match with experiments on dragon quest 8 nor disch's docs
+			//i changed it at the same time
+			bool mirror = addr.Bit(1);
+			if (mirror)
+				SetMirrorType(NES.NESBoardBase.EMirrorType.Horizontal);
+			else
+				SetMirrorType(NES.NESBoardBase.EMirrorType.Vertical);
+		}
 
 		public override void SyncState(Serializer ser)
-        {
+		{
 			base.SyncState(ser);
-            ser.Sync("prg", ref prg);
-            ser.Sync("mirror", ref mirror);
-        }
-    }
+			ser.Sync("prg", ref prg);
+		}
+	}
 }