NES - start mapper 245 prg mapping working (possibly)

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -191,6 +191,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper191.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper192.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper205.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper245.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\MMC3.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\NES-QJ.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\TQROM.cs" />

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MMC3_family/MMC3.cs

@@ -30,7 +30,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 		int irq_countdown;
 
 		//volatile state
-		ByteBuffer chr_regs_1k = new ByteBuffer(8);
+		public ByteBuffer chr_regs_1k = new ByteBuffer(8);
 		ByteBuffer prg_regs_8k = new ByteBuffer(4);
 
 		//configuration

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MMC3_family/Mapper245.cs

@@ -0,0 +1,105 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	class Mapper245 : MMC3Board_Base
+	{
+		/*
+		Here are Disch's original notes:  
+		========================
+		=  Mapper 245          =
+		========================
+
+
+		Example Games:
+		--------------------------
+		Chu Han Zheng Ba - The War Between Chu & Han
+		Xing Ji Wu Shi - Super Fighter
+		Yin He Shi Dai
+		Yong Zhe Dou e Long - Dragon Quest VII (As)
+		Dong Fang de Chuan Shuo - The Hyrule Fantasy
+
+
+		Notes:
+		---------------------------
+		Another ?Chinese? MMC3 clone.  Very similar to your typical MMC3.  For MMC3 info, see mapper 004.
+
+		Register layout is identical to a typical MMC3.
+
+
+
+		CHR Setup:
+		---------------------------
+
+		CHR-RAM is not swappable.  When there is no CHR-ROM present, 8k CHR-RAM is fixed.  However the CHR Mode bit
+		($8000.7) can still "flip" the left/right pattern tables.
+
+		Example:
+
+							$0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
+						+-------------------------------+-------------------------------+
+		CHR-RAM, Mode 0:  |             { 0 }             |             { 1 }             |
+						+-------------------------------+-------------------------------+
+		CHR-RAM, Mode 1:  |             { 1 }             |             { 0 }             |
+						+---------------------------------------------------------------+
+		CHR-ROM:          |                          Typical MMC3                         |
+						+---------------------------------------------------------------+
+
+
+		PRG Setup:
+		---------------------------
+
+		PRG Setup is the same as a normal MMC3, although there's a PRG-AND of $3F, and games select a 512k Block with
+		bit 1 of R:0.  Pretty simple really:
+
+		R:0:  [.... ..P.]
+
+		'P'    PRG-AND    PRG-OR
+		--------------------------
+		0       $3F        $00
+		1       $3F        $40
+
+ 
+		R:0 remains the normal MMC3 CHR reg, as well.  Although the game that uses it as a PRG block selector ("DQ7")
+		uses CHR-RAM, so it is normally ignored.
+		*/
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			//analyze board type
+			switch (Cart.board_type)
+			{
+				case "MAPPER245":
+					break;
+				default:
+					return false;
+			}
+
+			BaseSetup();
+			return true;
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			int bank_8k = Get_PRGBank_8K(addr);
+			bank_8k &= 0x3F;
+			bank_8k &= prg_mask;
+
+			int reg0 = ((base.mmc3.chr_regs_1k[0] >> 1) & 0x01);
+			if (reg0 == 1)
+			{
+				addr |= 0x40;
+			}
+			else
+			{
+				addr |= 0x00;
+			}
+
+			addr = (bank_8k << 13) | (addr & 0x1FFF);
+			return ROM[addr];
+		}
+	}
+}