From 0945049cd32f259bbbb6f125d6661cfe4e5db98c Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 31 Jul 2016 18:29:44 -0400
Subject: [PATCH] Made attempt to connect sync detect and then apply
 appropriate windowing, posting bytes to the appropriate place.

---
 Machines/Commodore/1540/C1540.cpp |  8 ++++++++
 Machines/Commodore/1540/C1540.hpp | 24 +++++++++++++++++-------
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/Machines/Commodore/1540/C1540.cpp b/Machines/Commodore/1540/C1540.cpp
index a8c916c32..b3287c9ec 100644
--- a/Machines/Commodore/1540/C1540.cpp
+++ b/Machines/Commodore/1540/C1540.cpp
@@ -116,6 +116,14 @@ void Machine::mos6522_did_change_interrupt_status(void *mos6522)
 void Machine::process_input_bit(int value, unsigned int cycles_since_index_hole)
 {
 	_shift_register = (_shift_register << 1) | value;
+	_driveVIA.set_sync_detected((_shift_register & 0x3ff) == 0x3ff);
+	if((_shift_register & 0x7ff) == 0x7fe) _bit_window_offset = 0;
+	_bit_window_offset++;
+	if(_bit_window_offset == 8)
+	{
+		_driveVIA.set_data_input((uint8_t)_shift_register);
+		_bit_window_offset = 0;
+	}
 }
 
 // the 1540 does not recognise index holes
diff --git a/Machines/Commodore/1540/C1540.hpp b/Machines/Commodore/1540/C1540.hpp
index 844341baa..a2b17f165 100644
--- a/Machines/Commodore/1540/C1540.hpp
+++ b/Machines/Commodore/1540/C1540.hpp
@@ -106,7 +106,7 @@ class SerialPortVIA: public MOS::MOS6522<SerialPortVIA>, public MOS::MOS6522IRQD
 		Bit 3:		LED control (TODO)
 		Bit 4:		write protect photocell status (TODO)
 		Bits 5/6:	write density (TODO)
-		Bit 7:		0 if sync marks are currently being detected, 1 otherwise;
+		Bit 7:		0 if sync marks are currently being detected, 1 otherwise.
 
 	... and Port A contains the byte most recently read from the disk or the byte next to write to the disk, depending on data direction.
 
@@ -117,12 +117,19 @@ class DriveVIA: public MOS::MOS6522<DriveVIA>, public MOS::MOS6522IRQDelegate {
 	public:
 		using MOS6522IRQDelegate::set_interrupt_status;
 
+		// write protect tab uncovered
+		DriveVIA() : _port_b(0xff), _port_a(0xff) {}
+
 		uint8_t get_port_input(Port port) {
-			if(port)
-			{
-				return 0xff;	// imply not sync, write protect tab uncovered
-			}
-			return 0xff;
+			return port ? _port_b : _port_a;
+		}
+
+		void set_sync_detected(bool sync_detected) {
+			_port_b = (_port_b & 0x7f) | (sync_detected ? 0x00 : 0x80);
+		}
+
+		void set_data_input(uint8_t value) {
+			_port_a = value;
 		}
 
 		void set_port_output(Port port, uint8_t value, uint8_t direction_mask) {
@@ -137,6 +144,9 @@ class DriveVIA: public MOS::MOS6522<DriveVIA>, public MOS::MOS6522IRQDelegate {
 //				}
 			}
 		}
+
+	private:
+		uint8_t _port_b, _port_a;
 };
 
 /*!
@@ -201,7 +211,7 @@ class Machine:
 
 		std::shared_ptr<Storage::Disk> _disk;
 
-		int _shift_register;
+		int _shift_register, _bit_window_offset;
 		virtual void process_input_bit(int value, unsigned int cycles_since_index_hole);
 		virtual void process_index_hole();
 };