From 9566c875328b58b28dd68c3a68eda2e425b0ccd1 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 5 Jun 2016 12:11:12 -0400
Subject: [PATCH] Added enough to the machine that the 6560 can now produce
 output if it wishes.

---
 Components/6560/6560.cpp  | 14 ++++++++++++++
 Components/6560/6560.hpp  |  5 +++++
 Machines/Vic-20/Vic20.cpp | 28 +++++++++++-----------------
 Machines/Vic-20/Vic20.hpp |  8 ++++++++
 4 files changed, 38 insertions(+), 17 deletions(-)

diff --git a/Components/6560/6560.cpp b/Components/6560/6560.cpp
index 7573de2d9..f1fa17ce4 100644
--- a/Components/6560/6560.cpp
+++ b/Components/6560/6560.cpp
@@ -19,3 +19,17 @@ MOS6560::MOS6560() :
 			"return vec3(1.0);"
 		"}");
 }
+
+void MOS6560::set_register(int address, uint8_t value)
+{
+	printf("%02x -> %d\n", value, address);
+}
+
+uint16_t MOS6560::get_address()
+{
+	return 0;
+}
+
+void MOS6560::set_graphics_value(uint8_t value)
+{
+}
diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 60d71395e..027e69bfd 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -18,6 +18,11 @@ class MOS6560 {
 		MOS6560();
 		Outputs::CRT::CRT *get_crt() { return _crt.get(); }
 
+		uint16_t get_address();
+		void set_graphics_value(uint8_t value);
+
+		void set_register(int address, uint8_t value);
+
 	private:
 		std::unique_ptr<Outputs::CRT::CRT> _crt;
 };
diff --git a/Machines/Vic-20/Vic20.cpp b/Machines/Vic-20/Vic20.cpp
index 74d0fa12c..38217047f 100644
--- a/Machines/Vic-20/Vic20.cpp
+++ b/Machines/Vic-20/Vic20.cpp
@@ -21,28 +21,22 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 {
 	set_reset_line(false);
 
+	// run the phase-1 part of this cycle, in which the VIC accesses memory
+	_mos6560->set_graphics_value(read_memory(_mos6560->get_address()));
+
+	// run the phase-2 part of the cycle, which is whatever the 6502 said it should be
 	if(isReadOperation(operation))
 	{
-		uint8_t returnValue = 0xff;
-
-		if(address < sizeof(_ram))
-			returnValue &= _ram[address];
-
-		if(address >= 0x8000 && address < 0x9000)
-			returnValue &= _characterROM[address&0x0fff];
-
-		if(address >= 0xc000 && address < 0xe000)
-			returnValue &= _basicROM[address&0x1fff];
-
-		if(address >= 0xe000)
-			returnValue &= _kernelROM[address&0x1fff];
-
-		*value = returnValue;
+		*value = read_memory(address);
 	}
 	else
 	{
-		if(address < sizeof(_ram))
-			_ram[address] = *value;
+		if(address < sizeof(_ram)) _ram[address] = *value;
+		else if((address&0xfff0) == 0x9000)
+		{
+			_mos6560->set_register(address - 0x9000, *value);
+		}
+		// TODO: the 6522
 	}
 
 	return 1;
diff --git a/Machines/Vic-20/Vic20.hpp b/Machines/Vic-20/Vic20.hpp
index 4c6f81416..1d528977f 100644
--- a/Machines/Vic-20/Vic20.hpp
+++ b/Machines/Vic-20/Vic20.hpp
@@ -45,6 +45,14 @@ class Machine: public CPU6502::Processor<Machine>, public CRTMachine::Machine {
 		uint8_t _kernelROM[0x2000];
 		uint8_t _ram[0x2000];
 
+		inline uint8_t read_memory(uint16_t address) {
+			if(address < sizeof(_ram)) return _ram[address];
+			else if(address >= 0x8000 && address < 0x9000) return _characterROM[address&0x0fff];
+			else if(address >= 0xc000 && address < 0xe000) return _basicROM[address&0x1fff];
+			else if(address >= 0xe000) return _kernelROM[address&0x1fff];
+			return 0xff;
+		}
+
 		std::unique_ptr<MOS::MOS6560> _mos6560;
 };