From 0e34e5f72813f80f488bb441033601a40d6f079c Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Tue, 31 May 2016 09:15:59 -0400
Subject: [PATCH] Fixes compumate mapper

Still WIP
Needs keyboard peripheral for further testing, but boots for now
---
 .../Consoles/Atari/2600/Mappers/mCM.cs        | 111 +++++++++++++++---
 1 file changed, 92 insertions(+), 19 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mCM.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mCM.cs
index aeca989106..4bcd71697b 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mCM.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Mappers/mCM.cs
@@ -1,5 +1,6 @@
 using BizHawk.Common;
 using BizHawk.Common.NumberExtensions;
+using System;
 
 namespace BizHawk.Emulation.Cores.Atari.Atari2600
 {
@@ -183,6 +184,8 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 		private bool _disableRam = true;
 		private bool _writeMode = false;
 		private int _column = 0;
+        public bool _func_key = false;
+        public bool _shift_key = false;
 
 		public override void Dispose()
 		{
@@ -197,8 +200,12 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			_disableRam = true;
 			_writeMode = true;
 			_column = 0;
+            _func_key = false;
+            _shift_key = false;
 
 			base.HardReset();
+
+
 		}
 
 		public override void SyncState(Serializer ser)
@@ -209,16 +216,62 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			ser.Sync("column", ref _column);
 			ser.Sync("disableRam", ref _disableRam);
 			ser.Sync("writeMode", ref _writeMode);
+            ser.Sync("FuncKey", ref _func_key);
+            ser.Sync("ShiftKey", ref _shift_key);
 
-			base.SyncState(ser);
+            base.SyncState(ser);
 		}
 
-		public override byte ReadMemory(ushort addr)
+
+
+		private byte ReadMem(ushort addr, bool peek)
 		{
-			if (addr < 0x1000)
+
+            // A unique feature of the keyboard is that it changes the operation of inputs 0-3 
+            // by holding them high in the no-button-pressed state.
+            // However exposing this behaviour to the rest of the system would be overly cunmbersome
+            // so instead we bypass these cases here
+
+
+            if ((addr & 0x000F) == 8 && (addr & 0x1080)==0 && addr<1000)
+            {
+                // if func key pressed
+                if (_func_key == true)
+                {
+                    return 0x80;
+                }
+                else
+                {
+                    return 0;
+                }
+
+            }
+            else if ((addr & 0x000F) == 9 && (addr & 0x1080) == 0 && addr < 1000)
+            {
+                return 0x80;
+            }
+            else if ((addr & 0x000F) == 0xA && (addr & 0x1080) == 0 && addr < 1000)
+            {
+                return 0x80;
+            }
+            else if ((addr & 0x000F) == 0xB && (addr & 0x1080) == 0 && addr < 1000)
+            {
+                // if shift key pressed
+                if (_shift_key == true)
+                {
+                    return 0x80;
+                }
+                else
+                {
+                    return 0;
+                }
+            }
+            else if (addr < 0x1000)
 			{
-				return base.ReadMemory(addr);
-			}
+                return base.ReadMemory(addr);
+            }
+                
+
 
 			// Lower 2K is always the first 2K of the ROM bank
 			// Upper 2K is also Rom if ram is enabled
@@ -233,16 +286,24 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				return _ram[addr & 0x7FF];
 			}
 
-			// Attempting to read while in write mode
-			throw new NotTestedException();
+            // Attempting to read while in write mode
+            //throw new NotTestedException();
+
+            return 0;
 		}
 
-		public override byte PeekMemory(ushort addr)
+        public override byte ReadMemory(ushort addr)
+        {
+            return ReadMem(addr, false);
+        }
+
+
+        public override byte PeekMemory(ushort addr)
 		{
-			return ReadMemory(addr);
+			return ReadMem(addr,true);
 		}
 
-		public override void WriteMemory(ushort addr, byte value)
+        private void WriteMem(ushort addr, byte value, bool poke)
 		{
 			//Mimicking the 6532 logic for accesing port A, for testing
 			var isPortA = false;
@@ -267,7 +328,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 					if (registerAddr == 0x00)
 					{
-						if (addr != 640)
+						if (addr != 640 && addr>=0x280) // register addresses are only above 0x280
 						{
 							// Write Output reg A
 							isPortA = true;
@@ -277,8 +338,8 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			}
 
 
-			//if (addr == 0x280) //Stella uses only 280
-			if (isPortA)
+			if (addr == 0x280 && !poke) //Stella uses only 280
+			//if (isPortA && !poke)
 			{
 				var bit5 = value.Bit(5);
 				var bit4 = value.Bit(4);
@@ -292,9 +353,9 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 
 				_bank4K = value & 0x03;
 
-				//D6 = 1 -> increase key column (0 to 9)
-				//D5 = 1 -> reset key column to 0 (if D4 = 0)
-				if (bit5  && !bit4)
+                //D6 = 1 -> increase key column (0 to 9)
+                //D5 = 1 -> reset key column to 0 (if D4 = 0)
+                if (bit5  && !bit4)
 				{
 					_column = 0;
 				}
@@ -312,8 +373,20 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 					_ram[addr & 0x7FF] = value;
 				}
 			}
-
-			base.WriteMemory(addr, value);
+            if (addr<0x1000) {
+                base.WriteMemory(addr, value);
+            }
+			
 		}
-	}
+
+        public override void WriteMemory(ushort addr, byte value)
+        {
+            WriteMem(addr, value, false);          
+        }
+
+        public override void PokeMemory(ushort addr, byte value)
+        {
+            WriteMem(addr, value, true);
+        }
+    }
 }