From 1d39da242786e53c12b5eeda7d02a5de5c4360c3 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@zeromus.org>
Date: Sun, 13 Mar 2011 02:58:29 +0000
Subject: [PATCH] [NES] decided how to implement EXP bus infrastructure, even
 though nothing uses it yet

---
 BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs | 4 ++++
 BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs        | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs
index 7038ceb52f..edd47b0d48 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/BoardSystem.cs
@@ -16,9 +16,11 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			byte ReadPRG(int addr);
 			byte ReadPPU(int addr); byte PeekPPU(int addr);
 			byte ReadPRAM(int addr);
+			byte ReadEXP(int addr);
 			void WritePRG(int addr, byte value);
 			void WritePPU(int addr, byte value);
 			void WritePRAM(int addr, byte value);
+			void WriteEXP(int addr, byte value);
 			byte[] SaveRam { get; }
 			byte[] WRAM { get; set; }
 			byte[] VRAM { get; set; }
@@ -109,6 +111,8 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			public virtual void WritePRAM(int addr, byte value) { }
 			public virtual byte ReadPRAM(int addr) { return 0xFF; }
 
+			public virtual void WriteEXP(int addr, byte value) { }
+			public virtual byte ReadEXP(int addr) { return 0xFF; }
 
 			public virtual void WritePPU(int addr, byte value)
 			{
diff --git a/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs b/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
index ce63714596..73e7e73ff3 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
@@ -202,7 +202,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			else if (addr < 0x2000) return ram[addr - 0x1800];
 			else if (addr < 0x4000) return ReadPPUReg(addr & 7);
 			else if (addr < 0x4020) return ReadReg(addr); //we're not rebasing the register just to keep register names canonical
-			else if (addr < 0x6000) return 0xFF; //exp rom
+			else if (addr < 0x6000) return board.ReadEXP(addr);
 			else if (addr < 0x8000) return board.ReadPRAM(addr);
 			else return board.ReadPRG(addr - 0x8000);
 		}
@@ -215,7 +215,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			else if (addr < 0x2000) ram[addr - 0x1800] = value;
 			else if (addr < 0x4000) WritePPUReg(addr & 7, value);
 			else if (addr < 0x4020) WriteReg(addr, value);  //we're not rebasing the register just to keep register names canonical
-			else if (addr < 0x6000) { } //exp rom
+			else if (addr < 0x6000) board.WriteEXP(addr, value); 
 			else if (addr < 0x8000) board.WritePRAM(addr, value);
 			else board.WritePRG(addr - 0x8000, value);
 		}