From bd20b355f07093d912e9ec03d7f71f10fbf7aa62 Mon Sep 17 00:00:00 2001
From: SaxxonPike <saxxonpike@gmail.com>
Date: Sat, 13 Jul 2019 14:06:23 -0500
Subject: [PATCH] C64: Writing to CPU port writes open bus data to 00/01

---
 .../Computers/Commodore64/C64.Motherboard.cs    | 17 +++++++++--------
 .../Commodore64/C64.MotherboardInterface.cs     |  6 +++---
 .../Computers/Commodore64/MOS/Chip6510.cs       |  6 +++---
 3 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Computers/Commodore64/C64.Motherboard.cs b/BizHawk.Emulation.Cores/Computers/Commodore64/C64.Motherboard.cs
index 15e05954b7..9151154a5a 100644
--- a/BizHawk.Emulation.Cores/Computers/Commodore64/C64.Motherboard.cs
+++ b/BizHawk.Emulation.Cores/Computers/Commodore64/C64.Motherboard.cs
@@ -38,8 +38,6 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 		public readonly Drive1541 DiskDrive;
 
 		// state
-		//public int address;
-		public int Bus;
 		public bool InputRead;
 		public bool Irq;
 		public bool Nmi;
@@ -79,9 +77,6 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 			Pla = new Chip90611401();
 			Ram = new Chip4864();
 			Serial = new SerialPort();
-			
-			Cpu.DebuggerStep = Execute;
-			DiskDrive.DebuggerStep = Execute;
 
 			switch (sidType)
 			{
@@ -149,6 +144,11 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 			BasicRom = new Chip23128();
 			CharRom = new Chip23128();
 			KernalRom = new Chip23128();
+			
+			if (Cpu != null)
+				Cpu.DebuggerStep = Execute;
+			if (DiskDrive != null)
+				DiskDrive.DebuggerStep = Execute;
 		}
 
 		public int ClockNumerator { get; }
@@ -178,7 +178,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 		// -----------------------------------------
 		public void HardReset()
 		{
-			Bus = 0xFF;
+			_lastReadVicAddress = 0x3FFF;
+			_lastReadVicData = 0xFF;
 			InputRead = false;
 
 			Cia0.HardReset();
@@ -198,7 +199,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 		public void SoftReset()
 		{
 			// equivalent to a hard reset EXCEPT cpu, color ram, memory
-			Bus = 0xFF;
+			_lastReadVicAddress = 0x3FFF;
+			_lastReadVicData = 0xFF;
 			InputRead = false;
 
 			Cia0.HardReset();
@@ -365,7 +367,6 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 				ser.EndSection();
 			}
 
-			ser.Sync(nameof(Bus), ref Bus);
 			ser.Sync(nameof(InputRead), ref InputRead);
 			ser.Sync(nameof(Irq), ref Irq);
 			ser.Sync(nameof(Nmi), ref Nmi);
diff --git a/BizHawk.Emulation.Cores/Computers/Commodore64/C64.MotherboardInterface.cs b/BizHawk.Emulation.Cores/Computers/Commodore64/C64.MotherboardInterface.cs
index 6ea70757ac..cfb9b5534d 100644
--- a/BizHawk.Emulation.Cores/Computers/Commodore64/C64.MotherboardInterface.cs
+++ b/BizHawk.Emulation.Cores/Computers/Commodore64/C64.MotherboardInterface.cs
@@ -43,9 +43,9 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 			return data;
 		}
 
-		private void Cpu_WriteMemoryPort(int addr, int val)
+		private void Cpu_WriteMemoryPort(int addr)
 		{
-			Pla.WriteMemory(addr, Bus);
+			Pla.WriteMemory(addr, ReadOpenBus());
 		}
 
 		private bool Glue_ReadIRQ()
@@ -84,7 +84,7 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64
 
 		private int Pla_ReadColorRam(int addr)
 		{
-			var result = Bus;
+			var result = ReadOpenBus();
 			result &= 0xF0;
 			result |= ColorRam.Read(addr);
 			return result;
diff --git a/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Chip6510.cs b/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Chip6510.cs
index e5bd61ff76..a79632d865 100644
--- a/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Chip6510.cs
+++ b/BizHawk.Emulation.Cores/Computers/Commodore64/MOS/Chip6510.cs
@@ -44,7 +44,7 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 		public Func<int, int> ReadMemory;
 		public Func<int> ReadPort;
 		public Action<int, int> WriteMemory;
-		public Action<int, int> WriteMemoryPort;
+		public Action<int> WriteMemoryPort;
 
 		public Action DebuggerStep;
 
@@ -161,11 +161,11 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.MOS
 			{
 				case 0x0000:
 					_port.Direction = val;
-					WriteMemoryPort(addr, val);
+					WriteMemoryPort(addr);
 					break;
 				case 0x0001:
 					_port.Latch = val;
-					WriteMemoryPort(addr, val);
+					WriteMemoryPort(addr);
 					break;
 				default:
 					if (ReadAec())