From 9498206980b0ab6c3092947e4c395bade5291d7b Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Mon, 23 Oct 2017 17:15:08 -0400
Subject: [PATCH] NESHawk: FDS Timer IRQ's

---
 .../Consoles/Nintendo/NES/FDS/FDS.cs          | 38 +++++++++----------
 .../Consoles/Nintendo/NES/FDS/RamAdapter.cs   |  7 +++-
 2 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/FDS.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/FDS.cs
index 9f46fdf560..e649c730e5 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/FDS.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/FDS.cs
@@ -255,19 +255,29 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				case 0x0020:
 					timerlatch &= 0xff00;
 					timerlatch |= value;
-					//timerirq = false;
 					break;
 				case 0x0021:
 					timerlatch &= 0x00ff;
 					timerlatch |= value << 8;
-					//timerirq = false;
 					break;
 				case 0x0022:
-					timerreg = (byte)(value & 3);
-					timervalue = timerlatch;
+					if (diskenable)
+					{
+						timerreg = (byte)(value & 3);
+						if ((value & 0x02) == 0x02)
+						{
+							timervalue = timerlatch;
+						}
+						else
+						{
+							_timerirq = false;
+						}
+					}
+					
 					break;
 				case 0x0023:
 					diskenable = (value & 1) != 0;
+					if (!diskenable) { _timerirq = false; }
 					soundenable = (value & 2) != 0;
 					break;
 				case 0x0024:
@@ -344,7 +354,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 
 		public override void ClockCPU()
 		{
-			if ((timerreg & 2) != 0)// && timervalue > 0)
+			if ((timerreg & 2) != 0 && diskenable)
 			{
 				if (timervalue!=0)
 				{
@@ -352,22 +362,12 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				}
 				if (timervalue == 0)
 				{
-
-					/*
-					if ((timerreg & 1) != 0)
-					{
-						timervalue = timerlatch;
-						//timervalue = 0xFFFF;
-					}
-					else
-					{
-						timerreg &= unchecked((byte)~2);
-						timervalue = 0;
-						timerlatch = 0;
-					}
-					*/
 					timervalue = timerlatch;
 					timerirq = true;
+					if ((timerreg & 1) == 0)
+					{
+						timerreg -= 2;
+					}
 				}
 			}
 			audio.Clock();
diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/RamAdapter.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/RamAdapter.cs
index 4861d49708..9c86f953e7 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/RamAdapter.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/NES/FDS/RamAdapter.cs
@@ -67,14 +67,17 @@ namespace BizHawk.Emulation.Cores.Nintendo.NES
 				byte[] fileheader = br.ReadBytes(16);
 				if (fileheader[0] != 0x03)
 				{
-					throw new Exception("Corrupt FDS block 3");
+					// Instead of exceptions, display strong warnings
+					Console.WriteLine("WARNING: INVALID FILE, BLOCK 3 ERROR");
+					//throw new Exception("Corrupt FDS block 3");
 				}
 				int filesize = fileheader[13] + fileheader[14] * 256;
 
 				byte[] file = br.ReadBytes(filesize + 1);
 				if (file[0] != 0x04)
 				{
-					throw new Exception("Corrupt FDS block 4");
+					Console.WriteLine("WARNING: INVALID FILE, BLOCK 4 ERROR");
+					//throw new Exception("Corrupt FDS block 4");
 				}
 
 				WriteBlock(ret, fileheader, 122);