From 6a773ac272bfd84038e74a3eaea973bb4a77ff67 Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Sat, 20 Jul 2019 14:47:36 -0400
Subject: [PATCH] Atari 2600: more bug fixes

---
 .../Consoles/Atari/2600/Tia/TIA.cs            | 46 ++++++++++++++++---
 .../Consoles/Atari/2600/Tia/Tia.MissleData.cs |  6 ++-
 .../Consoles/Atari/2600/Tia/Tia.PlayerData.cs | 17 ++++++-
 .../Consoles/Atari/2600/Tia/Tia.SyncState.cs  |  5 ++
 4 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
index 5140726551..4b9353f085 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/TIA.cs
@@ -104,6 +104,11 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 		private int _hmbDelay;
 		private byte _hmbVal;
 
+		private int _nusiz0Delay;
+		private byte _nusiz0Val;
+		private int _nusiz1Delay;
+		private byte _nusiz1Val;
+
 		private int _hmClrDelay;
 
 		private int _prg0Delay;
@@ -223,6 +228,11 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			_hmbDelay = 0;
 			_hmbVal = 0;
 
+			_nusiz0Delay = 0;
+			_nusiz0Val = 0;
+			_nusiz1Delay = 0;
+			_nusiz1Val = 0;
+
 			_prg0Delay = 0;
 			_prg1Delay = 0;
 			_prg0Val = 0;
@@ -404,6 +414,32 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				}
 			}
 
+			if (_nusiz0Delay > 0)
+			{
+				_nusiz0Delay++;
+				if (_nusiz0Delay == 4)
+				{
+					_nusiz0Delay = 0;
+
+					_player0.Nusiz = (byte)(_nusiz0Val & 0x37);
+					_player0.Missile.Size = (byte)((_nusiz0Val & 0x30) >> 4);
+					_player0.Missile.Number = (byte)(_nusiz0Val & 0x07);
+				}
+			}
+
+			if (_nusiz1Delay > 0)
+			{
+				_nusiz1Delay++;
+				if (_nusiz1Delay == 4)
+				{
+					_nusiz1Delay = 0;
+
+					_player1.Nusiz = (byte)(_nusiz1Val & 0x37);
+					_player1.Missile.Size = (byte)((_nusiz1Val & 0x30) >> 4);
+					_player1.Missile.Number = (byte)(_nusiz1Val & 0x07);
+				}
+			}
+
 			// Reset the RDY flag when we reach hblank
 			if (_hsyncCnt <= 0)
 			{
@@ -1054,15 +1090,13 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			}
 			else if (maskedAddr == 0x04) // NUSIZ0
 			{
-				_player0.Nusiz = (byte)(value & 0x37);
-				_player0.Missile.Size = (byte)((value & 0x30) >> 4);
-				_player0.Missile.Number = (byte)(value & 0x07);
+				_nusiz0Delay = 1;
+				_nusiz0Val = value;
 			}
 			else if (maskedAddr == 0x05) // NUSIZ1
 			{
-				_player1.Nusiz = (byte)(value & 0x37);
-				_player1.Missile.Size = (byte)((value & 0x30) >> 4);
-				_player1.Missile.Number = (byte)(value & 0x07);
+				_nusiz1Delay = 1;
+				_nusiz1Val = value;
 			}
 			else if (maskedAddr == 0x06) // COLUP0
 			{
diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.MissleData.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.MissleData.cs
index f6bab5dc25..38c579712b 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.MissleData.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.MissleData.cs
@@ -82,7 +82,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				{
 					_startSignal = HPosCnt;
 					_signalReached = HPosCnt + 5;
-					if (HPosCnt != 156) { _draw_signaled = true; }
+					_draw_signaled = true;
 				}
 
 				if (_startSignal < _signalReached)
@@ -111,6 +111,10 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 					{
 						_startSignal -= _startSignal - 60;
 					}
+					else if (_startSignal < 161)
+					{
+						_startSignal -= _startSignal - 156;
+					}
 				}
 			}
 
diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.PlayerData.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.PlayerData.cs
index 56773a173b..3d33f1426e 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.PlayerData.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.PlayerData.cs
@@ -1,5 +1,9 @@
 using BizHawk.Common;
 
+// TODO: Some of the values that are being latched (like Nusiz) are being latched based on the internal player ticks, not the external hsync ticks.
+// This can be seen for example in the player32_hblank test ROM. 
+// Which values these are exactly needs to be more carefully studied.
+
 namespace BizHawk.Emulation.Cores.Atari.Atari2600
 {
 	public partial class TIA
@@ -104,9 +108,13 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 							}
 						}
 					}
-					else
+					else if (ScanCntInit)
 					{
 						ScanCntInit = false;
+						//ScanCnt++;
+					}
+					else
+					{
 						ScanCnt++;
 					}
 				}
@@ -164,7 +172,7 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 				{
 					_startSignal = HPosCnt - 1;
 					_signalReached = HPosCnt + 5;
-					if (HPosCnt != 156) { _draw_signaled = true; }
+					_draw_signaled = true;
 				}
 
 				if (_startSignal < _signalReached)
@@ -193,6 +201,11 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 					{
 						_startSignal -= _startSignal - 60;
 					}
+
+					else if (_startSignal < 161)
+					{
+						_startSignal -= _startSignal - 156;
+					}
 				}
 			}
 
diff --git a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.SyncState.cs b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.SyncState.cs
index 8881944917..deb62d3a7b 100644
--- a/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.SyncState.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Atari/2600/Tia/Tia.SyncState.cs
@@ -51,6 +51,11 @@ namespace BizHawk.Emulation.Cores.Atari.Atari2600
 			ser.Sync("hmb_delay", ref _hmbDelay);
 			ser.Sync("hmb_val", ref _hmbVal);
 
+			ser.Sync("_nusiz0Delay", ref _nusiz0Delay);
+			ser.Sync("_nusiz0Val", ref _nusiz0Val);
+			ser.Sync("_nusiz1Delay", ref _nusiz1Delay);
+			ser.Sync("_nusiz1Val", ref _nusiz1Val);
+
 			ser.Sync("_hmClrDelay", ref _hmClrDelay);
 
 			ser.Sync("PRG0_delay", ref _prg0Delay);