TIA: Added blanking when HMOVE occurs.

Implemented playfield copying (fixes some Pacman display issues).
Added a document which discusses the inner workings of the TIA on a circuit level.
M6532: Added stubs for several registers, and changed the returns for some. Pitfall's first screen now renders correctly, and the copyright message scrolls.

BizHawk.Emulation/Consoles/Atari/2600/M6532.cs

@@ -58,6 +58,22 @@ namespace BizHawk.Emulation.Consoles.Atari
 				else
 				{
 					Console.WriteLine("6532 register read: " + maskedAddr.ToString("x"));
+					if (maskedAddr == 0x00) // SWCHA
+					{
+						return 0xFF;
+					}
+					else if (maskedAddr == 0x01) // SWACNT
+					{
+						
+					}
+					else if (maskedAddr == 0x02) // SWCHB
+					{
+						return 0x3F;
+					}
+					else if (maskedAddr == 0x03) // SWBCNT
+					{
+
+					}
 				}
 			}
 

BizHawk.Emulation/Consoles/Atari/2600/TIA.cs

@@ -13,6 +13,9 @@ namespace BizHawk.Emulation.Consoles.Atari
 		UInt32 PF; // PlayField data
 		byte BKcolor, PFcolor;
 		bool PFpriority = false;
+		bool PFreflect = false;
+
+		bool hmoveHappened = false;
 
 		struct playerData
 		{
@@ -127,12 +130,20 @@ namespace BizHawk.Emulation.Consoles.Atari
 			// Second half
 			else
 			{
-				PFmask = (UInt32)(1 << ((byte)((pixelPos % 80) / 4)));
+				if (PFreflect)
+				{
+					PFmask = (UInt32)(1 << ((byte)((pixelPos % 80) / 4)));
+				}
+				else
+				{
+					PFmask = (UInt32)(1 << ((20 - 1) - (byte)((pixelPos % 80) / 4)));
+				}
 			}
 
 			UInt32 color;
 			color = palette[BKcolor];
 
+
 			if ((PF & PFmask) != 0)
 			{
 				color = palette[PFcolor];
@@ -246,6 +257,15 @@ namespace BizHawk.Emulation.Consoles.Atari
 			{
 				color = 0x000000;
 			}
+
+			if (hmoveHappened && pixelPos >= 0 && pixelPos < 8)
+			{
+				color = 0x000000;
+			}
+			if (pixelPos >= 8)
+			{
+				hmoveHappened = false;
+			}
 			scanline[pixelPos]   = color;
 
 			scanlinePos++;
@@ -382,6 +402,7 @@ namespace BizHawk.Emulation.Consoles.Atari
 			else if (maskedAddr == 0x0A) // CTRLPF
 			{
 				PFpriority = (value & 0x04) != 0;
+				PFreflect = (value & 0x01) != 0;
 
 				ball.size = (byte)((value & 0x30) >> 4);
 			}
@@ -461,6 +482,7 @@ namespace BizHawk.Emulation.Consoles.Atari
 				player1.HM = 0;
 				ball.HM = 0;
 
+				hmoveHappened = true;
 			}
 		}