NES - implement board MLT-ACTION52 (Mapper 228) for both Action-52 and Cheetahmen II

BizHawk.Emulation/BizHawk.Emulation.csproj

@@ -178,6 +178,7 @@
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper60.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper61.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\Mapper62.cs" />
+    <Compile Include="Consoles\Nintendo\NES\Boards\MLT-ACTION52.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\HKROM.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper012.cs" />
     <Compile Include="Consoles\Nintendo\NES\Boards\MMC3_family\Mapper044.cs" />

BizHawk.Emulation/Consoles/Nintendo/NES/Boards/MLT-ACTION52.cs

@@ -0,0 +1,209 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace BizHawk.Emulation.Consoles.Nintendo
+{
+	class MLT_ACTION52 : NES.NESBoardBase
+	{
+		/*
+		 Here are Disch's original notes:
+		========================
+		=  Mapper 228          =
+		========================
+
+
+		Example Games:
+		--------------------------
+		Action 52
+		Cheetah Men II
+
+
+		Notes:
+		---------------------------
+		Cheetah Men II is infamous for how freaking terrible it is.  Action 52 is none better.  These games are SO
+		bad, it's hilarious.
+ 
+		Action 52's PRG size is weird (not a power of 2 value).  This is because there are 3 seperate 512k PRG chips.
+		PRG Setup section will cover details.
+
+
+		Powerup and Reset:
+		---------------------------
+		Apparently the games expect $00 to be written to $8000 on powerup/reset.
+
+
+		Registers:
+		---------------------------
+
+		$4020-4023:  [.... RRRR]  RAM  (readable/writable)
+		(16 bits of RAM -- 4 bits in each of the 4 regs)
+		$4024-5FFF:    mirrors $4020-4023
+
+		$8000-FFFF:    [.... ..CC]   Low 2 bits of CHR
+		A~[..MH HPPP PPO. CCCC]
+
+		M = Mirroring (0=Vert, 1=Horz)
+		H = PRG Chip Select
+		P = PRG Page Select
+		O = PRG Mode
+		C = High 4 bits of CHR
+
+		CHR Setup:
+		---------------------------
+
+		$0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
+		+---------------------------------------------------------------+
+		|                             $8000                             |
+		+---------------------------------------------------------------+
+
+
+		PRG Setup:
+		---------------------------
+
+		'H' bits select the PRG chip.  Each chip is 512k in size.  Chip 2 does not exist, and when selected, will
+		result in open bus.  The Action 52 .nes ROM file contains chips 0, 1, and 3:
+
+		chip 0:  offset 0x000010
+		chip 1:  offset 0x080010
+		chip 2:  -- non existant --
+		chip 3:  offset 0x100010
+
+		'P' selects the PRG page on the currently selected chip.
+
+		$8000   $A000   $C000   $E000  
+					+-------------------------------+
+		PRG Mode 0: |            <$8000>            |
+					+-------------------------------+
+		PRG Mode 1: |     $8000     |     $8000     |
+					+---------------+---------------+
+		*/
+		public bool prg_mode;
+		public int prg_reg;
+		public int chr_reg;
+		public int chip_offset;
+		public bool cheetahmen = false;
+		ByteBuffer eRAM = new ByteBuffer(4);
+		int chr_bank_mask_8k, prg_bank_mask_16k, prg_bank_mask_32k;
+
+		public override bool Configure(NES.EDetectionOrigin origin)
+		{
+			switch (Cart.board_type)
+			{
+				case "MAPPER228":
+				case "MLT-ACTION52":
+					break;
+				default:
+					return false;
+			}
+
+			chr_bank_mask_8k = Cart.chr_size / 8 - 1;
+			prg_bank_mask_16k = Cart.prg_size / 16 - 1;
+			prg_bank_mask_32k = Cart.prg_size / 32 - 1;
+
+			if (Cart.prg_size == 256)
+			{
+				cheetahmen = true;
+			}
+
+			prg_mode = false;
+			return true;
+		}
+
+		public override void SyncState(Serializer ser)
+		{
+			ser.Sync("prg_reg", ref prg_reg);
+			ser.Sync("chr_reg", ref chr_reg);
+			ser.Sync("prg_mode", ref prg_mode);
+			ser.Sync("chip", ref chip_offset);
+			ser.Sync("eRAM", ref eRAM);
+			base.SyncState(ser);
+		}
+
+		public override void Dispose()
+		{
+			eRAM.Dispose();
+			base.Dispose();
+		}
+
+		public override void WriteEXP(int addr, byte value)
+		{
+			if (addr >= 0x1800)
+			{
+				eRAM[(addr & 0x07)] = (byte)(value & 0x0F);
+			}
+		}
+
+		public override byte ReadEXP(int addr)
+		{
+			if (addr >= 0x1800)
+			{
+				return eRAM[(addr & 0x07)];
+			}
+			else
+			{
+				return base.ReadEXP(addr);
+			}
+		}
+
+		public override void WritePRG(int addr, byte value)
+		{
+			//$8000-FFFF:    [.... ..CC]   Low 2 bits of CHR
+			//A~[..MH HPPP PPO. CCCC]
+
+			if (addr.Bit(13))
+			{
+				SetMirrorType(EMirrorType.Horizontal);
+			}
+			else
+			{
+				SetMirrorType(EMirrorType.Vertical);
+			}
+
+			prg_mode = addr.Bit(5);
+			prg_reg = (addr >> 6) & 0x1F;
+			chr_reg = ((addr & 0x0F) << 2) | (value & 0x03);
+			if (!cheetahmen)
+			{
+				int chip = ((addr >> 11) & 0x03);
+				switch (chip)
+				{
+					case 0:
+						chip_offset = 0;
+						break;
+					case 1:
+						chip_offset = 0x80000;
+						break;
+					case 2:
+						break; //TODO: this chip doesn't exist and should access open bus
+					case 3:
+						chip_offset = 0x100000;
+						break;
+				}
+			}
+		}
+
+		public override byte ReadPPU(int addr)
+		{
+			if (addr < 0x2000)
+			{
+				return VROM[((chr_reg & chr_bank_mask_8k) * 0x2000) + addr];
+			}
+			return base.ReadPPU(addr);
+		}
+
+		public override byte ReadPRG(int addr)
+		{
+			if (prg_mode == false)
+			{
+				int bank = (prg_reg >> 1) & prg_bank_mask_32k;
+				return ROM[(bank * 0x8000) + addr + chip_offset];
+			}
+			else
+			{
+				return ROM[((prg_reg & prg_bank_mask_16k) * 0x4000) + (addr & 0x3FFF) + chip_offset];
+			}
+		}
+	}
+}