AppleWin/source/Disk.cpp

/*
AppleWin : An Apple //e emulator for Windows

Copyright (C) 1994-1996, Michael O'Brien
Copyright (C) 1999-2001, Oliver Schmidt
Copyright (C) 2002-2005, Tom Charlesworth
Copyright (C) 2006-2019, Tom Charlesworth, Michael Pohoreski, Nick Westgate

AppleWin is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

AppleWin is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with AppleWin; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* Description: Disk
 *
 * Author: Various
 *
 * In comments, UTAIIe is an abbreviation for a reference to "Understanding the Apple //e" by James Sather
 */

#include "StdAfx.h"

#include "Disk.h"

#include "Interface.h"
#include "Core.h"
#include "CardManager.h"
#include "CPU.h"
#include "DiskImage.h"
#include "Log.h"
#include "Memory.h"
#include "Registry.h"
#include "SaveState.h"
#include "YamlHelper.h"

#include "../resource/resource.h"

// About m_enhanceDisk:
// . In general m_enhanceDisk==false is used for authentic disk access speed, whereas m_enhanceDisk==true is for enhanced speed.
// Details:
// . if false: Used by ImageReadTrack() to skew the sectors in a track (for .do, .dsk, .po 5.25" images).
// . if true && m_floppyMotorOn, then this is a condition for full-speed (unthrottled) emulation mode.
// . if false && I/O ReadWrite($C0EC) && drive is spinning, then advance the track buffer's nibble index (to simulate spinning).
// Also m_enhanceDisk is persisted to the save-state, so it's an attribute of the DiskII interface card.

// NB. Non-standard 4&4, with Vol=0x00 and Chk=0x00 (only a few match, eg. Wasteland, Legacy of the Ancients, Planetfall, Border Zone & Wizardry). [*1]
const BYTE Disk2InterfaceCard::m_T00S00Pattern[] = {0xD5,0xAA,0x96,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0xDE};

Disk2InterfaceCard::Disk2InterfaceCard(UINT slot) :
	Card(CT_Disk2, slot),
	m_syncEvent(slot, 0, SyncEventCallback)	// use slot# as "unique" id for Disk2InterfaceCards
{
	if (m_slot != 5 && m_slot != 6)	// fixme
		ThrowErrorInvalidSlot();

	ResetSwitches();

	m_floppyLatch = 0;
	m_saveDiskImage = true;	// Save the DiskImage name to Registry
	m_diskLastCycle = 0;
	m_diskLastReadLatchCycle = 0;
	m_enhanceDisk = true;
	m_is13SectorFirmware = false;
	m_force13SectorFirmware = false;
	m_deferredStepperEvent = false;
	m_deferredStepperAddress = 0;
	m_deferredStepperCumulativeCycles = 0;

	ResetLogicStateSequencer();

	// Debug:
#if LOG_DISK_NIBBLES_USE_RUNTIME_VAR
	m_bLogDisk_NibblesRW = false;
#endif
#if LOG_DISK_NIBBLES_WRITE
	m_uWriteLastCycle = 0;
	m_uSyncFFCount = 0;
#endif
}

Disk2InterfaceCard::~Disk2InterfaceCard(void)
{
	EjectDiskInternal(DRIVE_1);
	EjectDiskInternal(DRIVE_2);

	if (m_syncEvent.m_active)
		g_SynchronousEventMgr.Remove(m_syncEvent.m_id);
}

bool Disk2InterfaceCard::GetEnhanceDisk(void) { return m_enhanceDisk; }
void Disk2InterfaceCard::SetEnhanceDisk(bool bEnhanceDisk) { m_enhanceDisk = bEnhanceDisk; }

UINT   Disk2InterfaceCard::GetCurrentBitOffset  (void) { return m_floppyDrive[m_currDrive].m_disk.m_bitOffset; }
double Disk2InterfaceCard::GetCurrentExtraCycles(void) { return m_floppyDrive[m_currDrive].m_disk.m_extraCycles; }
float  Disk2InterfaceCard::GetCurrentPhase      (void) { return m_floppyDrive[m_currDrive].m_phasePrecise; }
int    Disk2InterfaceCard::GetCurrentDrive      (void) { return m_currDrive; }
BYTE   Disk2InterfaceCard::GetCurrentShiftReg   (void) { return m_shiftReg; }
int    Disk2InterfaceCard::GetCurrentTrack      (void) { return ImagePhaseToTrack(m_floppyDrive[m_currDrive].m_disk.m_imagehandle, m_floppyDrive[m_currDrive].m_phasePrecise, false); }

float Disk2InterfaceCard::GetPhase(const int drive) { return m_floppyDrive[drive].m_phasePrecise; }
int   Disk2InterfaceCard::GetTrack(const int drive)  { return ImagePhaseToTrack(m_floppyDrive[drive].m_disk.m_imagehandle, m_floppyDrive[drive].m_phasePrecise, false); }

std::string Disk2InterfaceCard::FormatIntFracString(float phase, bool hex)
{
	const UINT phaseInt = (UINT)phase;
	const UINT phaseFrac = (UINT)((phase - (float)phaseInt) * 100 + 0.5);

	if (hex)
		return StrFormat("%02X.%02d", phaseInt, phaseFrac);	// (hex)"NN.nn"
	else
		return StrFormat("%02d.%02d", phaseInt, phaseFrac);	// (dec)"NN.nn"

}

std::string Disk2InterfaceCard::GetCurrentTrackString(void)
{
	return FormatIntFracString(m_floppyDrive[m_currDrive].m_phasePrecise / 2, true);
}

std::string Disk2InterfaceCard::GetCurrentPhaseString(void)
{
	return FormatIntFracString(m_floppyDrive[m_currDrive].m_phasePrecise, true);
}

LPCTSTR Disk2InterfaceCard::GetCurrentState(Disk_Status_e& eDiskState_)
{
	if (m_floppyDrive[m_currDrive].m_disk.m_imagehandle == NULL)
	{
		eDiskState_ = DISK_STATUS_EMPTY;
	}
	else
	if (!m_floppyMotorOn)
	{
		if (m_floppyDrive[m_currDrive].m_spinning > 0)
		{
			eDiskState_ = DISK_STATUS_SPIN;
		}
		else
		{
			eDiskState_ = DISK_STATUS_OFF;
		}
	}
	else if (m_seqFunc.writeMode)
	{
		if (m_floppyDrive[m_currDrive].m_disk.m_bWriteProtected)
		{
			eDiskState_ = DISK_STATUS_PROT;
		}
		else
		{
			eDiskState_ = DISK_STATUS_WRITE;
		}
	}
	else
	{
		/*if (m_seqFunc.loadMode)
		{
			if (m_floppyDrive[m_currDrive].disk.bWriteProtected)
				return "Reading write protect state (write protected)";
			else
				return "Reading write protect state (not write protected)";
		}
		else*/
		{
			eDiskState_ = DISK_STATUS_READ;
		}
	}

	static const char *aDiskStateMiniDesc[NUM_DISK_STATUS] =
	{
		 "Off"  // DISK_STATUS_OFF
		,"R"    // DISK_STATUS_READ
		,"W"    // DISK_STATUS_WRITE
		,"WP"   // DISK_STATUS_PROT
		,"n/a"  // DISK_STATUS_EMPTY
		,"Spin" // DISK_STATUS_SPIN
	};

	return aDiskStateMiniDesc[eDiskState_];
}

//===========================================================================

void Disk2InterfaceCard::LoadLastDiskImage(const int drive)
{
	_ASSERT(drive == DRIVE_1 || drive == DRIVE_2);

	const std::string regKey = (drive == DRIVE_1)
		? REGVALUE_LAST_DISK_1
		: REGVALUE_LAST_DISK_2;

	char pathname[MAX_PATH];

	std::string regSection = RegGetConfigSlotSection(m_slot);
	if (RegLoadString(regSection.c_str(), regKey.c_str(), TRUE, pathname, MAX_PATH, TEXT("")) && (pathname[0] != 0))
	{
		m_saveDiskImage = false;
		ImageError_e error = InsertDisk(drive, pathname, IMAGE_USE_FILES_WRITE_PROTECT_STATUS, IMAGE_DONT_CREATE);
		m_saveDiskImage = true;

		if (error != eIMAGE_ERROR_NONE)
		{
			NotifyInvalidImage(drive, pathname, error);
			EjectDisk(drive);
		}
	}
}

//===========================================================================

void Disk2InterfaceCard::SaveLastDiskImage(const int drive)
{
	_ASSERT(drive == DRIVE_1 || drive == DRIVE_2);

	if (!m_saveDiskImage)
		return;

	std::string regSection = RegGetConfigSlotSection(m_slot);
	RegSaveValue(regSection.c_str(), REGVALUE_CARD_TYPE, TRUE, CT_Disk2);

	const std::string regKey = (drive == DRIVE_1)
		? REGVALUE_LAST_DISK_1
		: REGVALUE_LAST_DISK_2;

	const std::string& pathName = DiskGetFullPathName(drive);

	RegSaveString(regSection.c_str(), regKey.c_str(), TRUE, pathName);

	//

	// For now, only update 'Starting Directory' for slot6 & drive1
	// . otherwise you'll get inconsistent results if you set drive1, then drive2 (and the images were in different folders)
	if (m_slot != SLOT6 || drive != DRIVE_1)
		return;

	const size_t slash = pathName.find_last_of(PATH_SEPARATOR);
	if (slash != std::string::npos)
	{
		const std::string dirName = pathName.substr(0, slash + 1);
		RegSaveString(REG_PREFS, REGVALUE_PREF_START_DIR, 1, dirName);
	}
}

//===========================================================================

// Called by ControlMotor() & Enable()
void Disk2InterfaceCard::CheckSpinning(const bool stateChanged, const ULONG uExecutedCycles)
{
	bool modeChanged = m_floppyMotorOn && !m_floppyDrive[m_currDrive].m_spinning;

	if (m_floppyMotorOn && IsDriveConnected(m_currDrive))
		m_floppyDrive[m_currDrive].m_spinning = SPINNING_CYCLES;

	if (modeChanged)
		GetFrame().FrameDrawDiskLEDS();

	if (modeChanged)
	{
		// Set m_diskLastCycle when motor changes: not spinning (ie. off for 1 sec) -> on
		m_diskLastCycle = g_nCumulativeCycles;
	}

	if (m_floppyMotorOn && stateChanged)
	{
		// Set m_motorOnCycle when: motor changes to on, or the other drive is enabled (and motor is on)
		m_floppyDrive[m_currDrive].m_motorOnCycle = g_nCumulativeCycles;
	}
}

//===========================================================================

bool Disk2InterfaceCard::IsDriveValid(const int drive)
{
	return (drive >= 0 && drive < NUM_DRIVES);
}

//===========================================================================

void Disk2InterfaceCard::AllocTrack(const int drive, const UINT minSize/*=NIBBLES_PER_TRACK*/)
{
	FloppyDisk* pFloppy = &m_floppyDrive[drive].m_disk;
	const UINT maxNibblesPerTrack = ImageGetMaxNibblesPerTrack(m_floppyDrive[drive].m_disk.m_imagehandle);
	pFloppy->m_trackimage = new BYTE[ MAX(minSize,maxNibblesPerTrack) ];
}

//===========================================================================

void Disk2InterfaceCard::ReadTrack(const int drive, ULONG uExecutedCycles)
{
	if (!IsDriveValid( drive ))
		return;

	FloppyDrive* pDrive = &m_floppyDrive[ drive ];
	FloppyDisk* pFloppy = &pDrive->m_disk;

	if (ImagePhaseToTrack(pFloppy->m_imagehandle, pDrive->m_phasePrecise, false) >= ImageGetNumTracks(pFloppy->m_imagehandle))
	{
		_ASSERT(0);	// What can cause this? Add a comment to replace this assert.
		// Boot with DOS 3.3 Master in D1
		// Create a blank disk in D2
		// INIT HELLO,D2
		// RUN HELLO
		// F2 to reboot DOS 3.3 Master
		// RUN HELLO,D2
		pFloppy->m_trackimagedata = false;
		return;
	}

	if (!pFloppy->m_trackimage)
		AllocTrack( drive );

	if (pFloppy->m_trackimage && pFloppy->m_imagehandle)
	{
		if (ImageIsWOZ(pFloppy->m_imagehandle))
		{
			// Update bitStream position for *current* track before re-calc'ing position for new track
			UINT bitCellDelta = GetBitCellDelta(uExecutedCycles);
			UpdateBitStreamPosition(*pFloppy, bitCellDelta);
		}

		if (ImageIsWOZ(pFloppy->m_imagehandle) && (pFloppy->m_bitCount == 0))
		{
			// WOZ: m_bitCount only ever 0 on initial power on
			pFloppy->m_bitOffset = 0;
			pFloppy->m_bitCount = 8;
		}

		const UINT32 currentBitPosition = pFloppy->m_bitOffset;
		const UINT32 currentBitTrackLength = pFloppy->m_bitCount;

		ImageReadTrack(
			pFloppy->m_imagehandle,
			pDrive->m_phasePrecise,
			pFloppy->m_trackimage,
			&pFloppy->m_nibbles,
			&pFloppy->m_bitCount,
			m_enhanceDisk);

		if (!ImageIsWOZ(pFloppy->m_imagehandle))
		{
			pFloppy->m_byte = 0;
		}
		else
		{
			// NB. This function is only called for a new track when there's a latch read, ie. only for *even* DEVICE SELECT I/O accesses.
			// . So when seeking across tracks (ie. sequencing through the magnet phases), then not all (quarter) tracks will need reading.
			// . eg. for 'Balance of Power'(GH#1022), for seek T00->T35: this only reads: 00.00, 00.25, 00.75, 01.25, 01.75, ... 34.25, 34.75, 35.00 (skipping the NN.00, NN.50 tracks).
			// . And so the bitOffset "round-up" below isn't called for every track.
			// TODO: consider forcing this function be be called for every track (and appropriately adjust the "round-up" amount - ie. halve it)

			_ASSERT(pFloppy->m_nibbles && pFloppy->m_bitCount);
			if (pFloppy->m_nibbles == 0 || pFloppy->m_bitCount == 0)
			{
				pFloppy->m_nibbles = 1;
				pFloppy->m_bitCount = 8;
			}

			pFloppy->m_bitOffset = (currentBitPosition * pFloppy->m_bitCount) / currentBitTrackLength;	// Ref: WOZ-1.01
			pFloppy->m_bitOffset += 7;	// Round-up for sensitive cross-track sync check (GH#1022)

			if (pFloppy->m_bitOffset >= pFloppy->m_bitCount)
				pFloppy->m_bitOffset = 0;
#if LOG_DISK_WOZ_READTRACK
			LOG_DISK("T%05.2f: %04X->%04X, Len=%04X\n", pDrive->m_phasePrecise / 2, currentBitPosition, pFloppy->m_bitOffset, pFloppy->m_bitCount);
#endif

			pFloppy->m_byte = pFloppy->m_bitOffset / 8;
			pFloppy->m_bitMask = 1 << (7 - (pFloppy->m_bitOffset % 8));

			pFloppy->m_extraCycles = 0.0;
			pDrive->m_headWindow = 0;

			FindTrackSeamWOZ(*pFloppy, pDrive->m_phasePrecise/2);
		}

		pFloppy->m_trackimagedata = (pFloppy->m_nibbles != 0);

		pFloppy->m_initialBitOffset = pFloppy->m_bitOffset;
		pFloppy->m_revs = 0;
	}
}

//===========================================================================

void Disk2InterfaceCard::EjectDiskInternal(const int drive)
{
	FloppyDisk* pFloppy = &m_floppyDrive[drive].m_disk;

	if (pFloppy->m_imagehandle)
	{
		FlushCurrentTrack(drive);

		ImageClose(pFloppy->m_imagehandle);
		pFloppy->m_imagehandle = NULL;
	}

	if (pFloppy->m_trackimage)
	{
		delete [] pFloppy->m_trackimage;
		pFloppy->m_trackimage = NULL;
		pFloppy->m_trackimagedata = false;
	}

	pFloppy->m_imagename.clear();
	pFloppy->m_fullname.clear();
	pFloppy->m_strFilenameInZip = "";
}

void Disk2InterfaceCard::EjectDisk(const int drive)
{
	if (!IsDriveValid(drive))
		return;

	EjectDiskInternal(drive);
	Snapshot_UpdatePath();

	SaveLastDiskImage(drive);
	GetFrame().Video_ResetScreenshotCounter("");
}

void Disk2InterfaceCard::UnplugDrive(const int drive)
{
	if (!IsDriveValid(drive))
		return;

	EjectDisk(drive);

	m_floppyDrive[drive].m_isConnected = false;
}

//===========================================================================

void Disk2InterfaceCard::WriteTrack(const int drive)
{
	FloppyDrive* pDrive = &m_floppyDrive[ drive ];
	FloppyDisk* pFloppy = &pDrive->m_disk;

	if (ImagePhaseToTrack(pFloppy->m_imagehandle, pDrive->m_phasePrecise, false) >= ImageGetNumTracks(pFloppy->m_imagehandle))
	{
		_ASSERT(0);	// What can cause this? Add a comment to replace this assert.
		return;
	}

	if (pFloppy->m_bWriteProtected)
		return;

	if (pFloppy->m_trackimage && pFloppy->m_imagehandle)
	{
#if LOG_DISK_TRACKS
		LOG_DISK("track $%s write\r\n", GetCurrentTrackString().c_str());
#endif
		ImageWriteTrack(
			pFloppy->m_imagehandle,
			pDrive->m_phasePrecise,
			pFloppy->m_trackimage,
			pFloppy->m_nibbles);
	}

	pFloppy->m_trackimagedirty = false;
}

void Disk2InterfaceCard::FlushCurrentTrack(const int drive)
{
	FloppyDisk* pFloppy = &m_floppyDrive[drive].m_disk;

	if (pFloppy->m_trackimage && pFloppy->m_trackimagedirty)
		WriteTrack(drive);
}

//===========================================================================

void Disk2InterfaceCard::Boot(void)
{
	// THIS FUNCTION RELOADS A PROGRAM IMAGE IF ONE IS LOADED IN DRIVE ONE.
	// IF A DISK IMAGE OR NO IMAGE IS LOADED IN DRIVE ONE, IT DOES NOTHING.
	if (m_floppyDrive[0].m_disk.m_imagehandle && ImageBoot(m_floppyDrive[0].m_disk.m_imagehandle))
		m_floppyMotorOn = 0;
}

//===========================================================================

void __stdcall Disk2InterfaceCard::ControlMotor(WORD, WORD address, BYTE, BYTE, ULONG uExecutedCycles)
{
	BOOL newState = address & 1;
	bool stateChanged = (newState != m_floppyMotorOn);

	if (stateChanged)
	{
		m_floppyMotorOn = newState;
		m_formatTrack.DriveNotWritingTrack();
	}

	// NB. Motor off doesn't reset the Command Decoder like reset. (UTAIIe figures 9.7 & 9.8 chip C2)
	// - so it doesn't reset this state: m_seqFunc, m_magnetStates
#if LOG_DISK_MOTOR
	LOG_DISK("%08X: motor %s\r\n", (UINT32)g_nCumulativeCycles, (m_floppyMotorOn) ? "on" : "off");
#endif
	CheckSpinning(stateChanged, uExecutedCycles);
}

//===========================================================================

void __stdcall Disk2InterfaceCard::ControlStepper(WORD, WORD address, BYTE, BYTE, ULONG uExecutedCycles)
{
	FloppyDrive* pDrive = &m_floppyDrive[m_currDrive];

	if (!m_floppyMotorOn)	// GH#525
	{
		if (!pDrive->m_spinning)
		{
#if LOG_DISK_PHASES
			LOG_DISK("stepper accessed whilst motor is off and not spinning\r\n");
#endif
			return;
		}

#if LOG_DISK_PHASES
		LOG_DISK("stepper accessed whilst motor is off, but still spinning\r\n");
#endif
	}

	// update phases (magnet states)
	{
		const int phase = (address >> 1) & 3;
		const int phase_bit = (1 << phase);

		// update the magnet states
		if (address & 1)
			m_magnetStates |= phase_bit;	// phase on
		else
			m_magnetStates &= ~phase_bit;	// phase off
	}

	if (!GetCardMgr().GetDisk2CardMgr().IsStepperDeferred())
	{
		m_deferredStepperAddress = address;
		m_deferredStepperCumulativeCycles = g_nCumulativeCycles;
		ControlStepperDeferred();
		return;
	}

	if (m_syncEvent.m_active)
	{
		// Check for adjacent magnets being turned off/on in a very short interval (10 cycles is purely based on A2osX). (GH#1110)
		g_SynchronousEventMgr.Remove(m_syncEvent.m_id);
		m_deferredStepperEvent = false;

		int addrDelta = (m_deferredStepperAddress & 7) - (address & 7);
		if (addrDelta < 0) addrDelta = -addrDelta;
		if (addrDelta == 2 || addrDelta == 6)	// adjacent magnets: both turned off or both turned on
		{
			if ((address & 1) == 0)	// adjacent magnets off
			{
				// 2 adjacent magnets off in quick succession don't move the cog (GH#1110)
				// . also DOS3.2, Pascal and ProDOS rapidly turning off all 4 magnets.
				ControlStepperLogging(m_deferredStepperAddress, m_deferredStepperCumulativeCycles);
				ControlStepperLogging(address, g_nCumulativeCycles);
				return;
			}
			else	// adjacent magnets turned on
			{
				// take no action - can't find any titles that ever do this!
				const std::string msg = "Disk: ControlStepper() - adjacent magnets turned on\n";
				LogOutput("%s", msg.c_str());
				LogFileOutput("%s", msg.c_str());
			}
		}

		// complete the deferred stepper event
		// eg. Glutton, EDD III - both just combinations of turning off all 4 magnets
		ControlStepperDeferred();
	}

	// defer the effect of changing the phase
	m_deferredStepperAddress = address;
	m_deferredStepperCumulativeCycles = g_nCumulativeCycles;
	InsertSyncEvent();
	m_deferredStepperEvent = true;
}

void Disk2InterfaceCard::InsertSyncEvent(void)
{
	m_syncEvent.m_cyclesRemaining = 10;	// NB. same cycle delay for magnet off and on - but perhaps they take different times?
	g_SynchronousEventMgr.Insert(&m_syncEvent);
}

int Disk2InterfaceCard::SyncEventCallback(int id, int cycles, ULONG uExecutedCycles)
{
	Disk2InterfaceCard& disk2Card = dynamic_cast<Disk2InterfaceCard&>(GetCardMgr().GetRef(id));
	disk2Card.ControlStepperDeferred();
	return 0;	// Don't repeat event
}

void Disk2InterfaceCard::ControlStepperDeferred(void)
{
	m_deferredStepperEvent = false;
	const WORD address = m_deferredStepperAddress;

	FloppyDrive* pDrive = &m_floppyDrive[m_currDrive];
	FloppyDisk* pFloppy = &pDrive->m_disk;

	// check for any stepping effect from a magnet
	// - move only when the magnet opposite the cog is off
	// - move in the direction of an adjacent magnet if one is on
	// - do not move if both adjacent magnets are on (ie. quarter track)
	// - timing is accounted for in the case when "two phases [are] turned off in rapid sequence" (UTAIIe page 9-13) (GH#1110)
	// momentum is not accounted for ... maybe one day!
	int direction = 0;
	if (m_magnetStates & (1 << ((pDrive->m_phase + 1) & 3)))
		direction += 1;
	if (m_magnetStates & (1 << ((pDrive->m_phase + 3) & 3)))
		direction -= 1;

	// Only calculate quarterDirection for WOZ, as NIB/DSK don't support half phases.
	int quarterDirection = 0;
	if (ImageIsWOZ(pFloppy->m_imagehandle))
	{
		if ((m_magnetStates == 0xC ||	// 1100
			m_magnetStates == 0x6 ||	// 0110
			m_magnetStates == 0x3 ||	// 0011
			m_magnetStates == 0x9))		// 1001
		{
			quarterDirection = direction;
			direction = 0;
		}
	}

	pDrive->m_phase = MAX(0, MIN(79, pDrive->m_phase + direction));
	float newPhasePrecise = (float)(pDrive->m_phase) + (float)quarterDirection * 0.5f;
	if (newPhasePrecise < 0)
		newPhasePrecise = 0;

	// apply magnet step, if any
	if (newPhasePrecise != pDrive->m_phasePrecise)
	{
		FlushCurrentTrack(m_currDrive);
		pDrive->m_phasePrecise = newPhasePrecise;
		pFloppy->m_trackimagedata = false;
		m_formatTrack.DriveNotWritingTrack();
		GetFrame().FrameDrawDiskStatus();	// Show track status (GH#201)
	}

	ControlStepperLogging(address, m_deferredStepperCumulativeCycles);
}

void Disk2InterfaceCard::ControlStepperLogging(WORD address, unsigned __int64 cumulativeCycles)
{
	FloppyDrive* pDrive = &m_floppyDrive[m_currDrive];

#if LOG_DISK_PHASES
	const ULONG cycleDelta = (ULONG)(cumulativeCycles - pDrive->m_lastStepperCycle);
#endif
	pDrive->m_lastStepperCycle = cumulativeCycles;	// NB. Persisted to save-state

#if LOG_DISK_PHASES
	LOG_DISK("%08X: track $%s magnet-states %d%d%d%d phase %d %s address $%4X last-stepper %.3fms\r\n",
		(UINT32)cumulativeCycles,
		GetCurrentTrackString().c_str(),
		(m_magnetStates >> 3) & 1,
		(m_magnetStates >> 2) & 1,
		(m_magnetStates >> 1) & 1,
		(m_magnetStates >> 0) & 1,
		(address >> 1) & 3,	// phase
		(address & 1) ? "on " : "off",
		address,
		((float)cycleDelta) / (CLK_6502_NTSC / 1000.0));
#endif
}

//===========================================================================

void Disk2InterfaceCard::Destroy(void)
{
	m_saveDiskImage = false;
	EjectDisk(DRIVE_1);

	m_saveDiskImage = false;
	EjectDisk(DRIVE_2);

	m_saveDiskImage = true;
}

//===========================================================================

bool __stdcall Disk2InterfaceCard::Enable(WORD, WORD address, BYTE, BYTE, ULONG uExecutedCycles)
{
	WORD newDrive = address & 1;
	bool stateChanged = (newDrive != m_currDrive);

	m_currDrive = newDrive;
#if LOG_DISK_ENABLE_DRIVE
	LOG_DISK("%08X: enable drive: %d\r\n", (UINT32)g_nCumulativeCycles, m_currDrive);
#endif
	m_floppyDrive[!m_currDrive].m_spinning   = 0;
	m_floppyDrive[!m_currDrive].m_writelight = 0;
	CheckSpinning(stateChanged, uExecutedCycles);

	return ImageIsWOZ(m_floppyDrive[m_currDrive].m_disk.m_imagehandle);		// Drive may've changed, so image-type may've changed
}

//===========================================================================

// Return the filename
// . Used by Drive Buttons' tooltips
const std::string & Disk2InterfaceCard::GetFullDiskFilename(const int drive)
{
	if (!m_floppyDrive[drive].m_disk.m_strFilenameInZip.empty())
		return m_floppyDrive[drive].m_disk.m_strFilenameInZip;

	return GetFullName(drive);
}

// Return the file or zip name
// . Used by Property Sheet Page (Disk)
const std::string & Disk2InterfaceCard::GetFullName(const int drive)
{
	return m_floppyDrive[drive].m_disk.m_fullname;
}

// Return the imagename
// . Used by Drive Button's icons & Property Sheet Page (Save snapshot)
const std::string & Disk2InterfaceCard::GetBaseName(const int drive)
{
	return m_floppyDrive[drive].m_disk.m_imagename;
}

void Disk2InterfaceCard::GetFilenameAndPathForSaveState(std::string& filename, std::string& path)
{
	filename = "";
	path = "";

	for (UINT i=DRIVE_1; i<=DRIVE_2; i++)
	{
		if (IsDriveEmpty(i))
			continue;

		filename = GetBaseName(i);
		std::string pathname = DiskGetFullPathName(i);

		int idx = pathname.find_last_of(PATH_SEPARATOR);
		if (idx >= 0 && idx+1 < (int)pathname.length())	// path exists?
		{
			path = pathname.substr(0, idx+1);
			return;
		}

		_ASSERT(0);
		break;
	}
}

const std::string & Disk2InterfaceCard::DiskGetFullPathName(const int drive)
{
	return ImageGetPathname(m_floppyDrive[drive].m_disk.m_imagehandle);
}

//===========================================================================

Disk_Status_e Disk2InterfaceCard::GetDriveLightStatus(const int drive)
{
	if (IsDriveValid( drive ))
	{
		FloppyDrive* pDrive = &m_floppyDrive[ drive ];

		if (pDrive->m_spinning)
		{
			if (pDrive->m_disk.m_bWriteProtected)
				return DISK_STATUS_PROT;

			if (pDrive->m_writelight)
				return DISK_STATUS_WRITE;
			else
				return DISK_STATUS_READ;
		}
		else
		{
			return DISK_STATUS_OFF;
		}
	}

	return DISK_STATUS_EMPTY;
}

void Disk2InterfaceCard::GetLightStatus(Disk_Status_e *pDisk1Status, Disk_Status_e *pDisk2Status)
{
	if (pDisk1Status)
		*pDisk1Status = GetDriveLightStatus(DRIVE_1);

	if (pDisk2Status)
		*pDisk2Status = GetDriveLightStatus(DRIVE_2);
}

//===========================================================================

// Pre: pathname likely to include path (but can also just be filename)
ImageError_e Disk2InterfaceCard::InsertDisk(const int drive, const std::string& pathname, const bool bForceWriteProtected, const bool bCreateIfNecessary)
{
	FloppyDrive* pDrive = &m_floppyDrive[drive];
	FloppyDisk* pFloppy = &pDrive->m_disk;

	if (pFloppy->m_imagehandle)
		EjectDisk(drive);

	// Reset the disk's attributes, but preserve the drive's attributes (GH#138/Platoon, GH#640)
	// . Changing the disk (in the drive) doesn't affect the drive's attributes.
	pFloppy->clear();

	const DWORD dwAttributes = GetFileAttributes(pathname.c_str());
	if (dwAttributes == INVALID_FILE_ATTRIBUTES)
		pFloppy->m_bWriteProtected = false;	// Assume this is a new file to create (so it must be write-enabled to allow it to be formatted)
	else
		pFloppy->m_bWriteProtected = bForceWriteProtected ? true : (dwAttributes & FILE_ATTRIBUTE_READONLY);

	// Check if image is being used by the other drive, and if so remove it in order so it can be swapped
	{
		const std::string & pszOtherPathname = DiskGetFullPathName(!drive);

		char szCurrentPathname[MAX_PATH]; 
		DWORD uNameLen = GetFullPathName(pathname.c_str(), MAX_PATH, szCurrentPathname, NULL);
		if (uNameLen == 0 || uNameLen >= MAX_PATH)
			strcpy_s(szCurrentPathname, MAX_PATH, pathname.c_str());

		if (!strcmp(pszOtherPathname.c_str(), szCurrentPathname))
		{
			EjectDisk(!drive);
			GetFrame().FrameRefreshStatus(DRAW_LEDS | DRAW_BUTTON_DRIVES | DRAW_DISK_STATUS);
		}
	}

	ImageError_e Error = ImageOpen(pathname,
		&pFloppy->m_imagehandle,
		&pFloppy->m_bWriteProtected,
		bCreateIfNecessary,
		pFloppy->m_strFilenameInZip);

	if (Error == eIMAGE_ERROR_NONE && ImageIsMultiFileZip(pFloppy->m_imagehandle))
	{
		std::string strText = StrFormat("Only the first file in a multi-file zip is supported\n"
										"Use disk image '%s' ?",
										pFloppy->m_strFilenameInZip.c_str());
		int nRes = GetFrame().FrameMessageBox(strText.c_str(), "Multi-Zip Warning", MB_ICONWARNING | MB_YESNO | MB_SETFOREGROUND);
		if (nRes == IDNO)
		{
			EjectDisk(drive);
			Error = eIMAGE_ERROR_REJECTED_MULTI_ZIP;
		}
	}

	if (Error == eIMAGE_ERROR_NONE)
	{
		GetImageTitle(pathname.c_str(), pFloppy->m_imagename, pFloppy->m_fullname);
		Snapshot_UpdatePath();

		GetFrame().Video_ResetScreenshotCounter(pFloppy->m_imagename);

		if (g_nAppMode == MODE_LOGO)
			InitFirmware(GetCxRomPeripheral());
	}
	else
	{
		GetFrame().Video_ResetScreenshotCounter("");
	}

	SaveLastDiskImage(drive);
	
	return Error;
}

//===========================================================================

bool Disk2InterfaceCard::IsConditionForFullSpeed(void)
{
	return m_floppyMotorOn && m_enhanceDisk;
}

//===========================================================================

void Disk2InterfaceCard::NotifyInvalidImage(const int drive, const std::string & szImageFilename, const ImageError_e Error)
{
	std::string strText;
	const char * pszImageFilename = szImageFilename.c_str();

	switch (Error)
	{
	case eIMAGE_ERROR_UNABLE_TO_OPEN:
	case eIMAGE_ERROR_UNABLE_TO_OPEN_GZ:
	case eIMAGE_ERROR_UNABLE_TO_OPEN_ZIP:
		strText = StrFormat("Unable to open the file %s.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_BAD_SIZE:
		strText = StrFormat("Unable to use the file %s\n"
							"because the disk image is an unsupported size.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_BAD_FILE:
		strText = StrFormat("Unable to use the file %s\n"
							"because the OS can't access it.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_UNSUPPORTED:
		strText = StrFormat("Unable to use the file %s\n"
							"because the disk image format is not recognized.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_UNSUPPORTED_HDV:
		strText = StrFormat("Unable to use the file %s\n"
							"because this UniDisk 3.5/Apple IIGS/hard-disk image is not supported.\n"
							"Try inserting as a hard-disk image instead.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_GZ:
	case eIMAGE_ERROR_ZIP:
		strText = StrFormat("Unable to use the compressed file %s\n"
							"because the compressed disk image is corrupt/unsupported.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_FAILED_TO_GET_PATHNAME:
		strText = StrFormat("Unable to GetFullPathName() for the file: %s.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_ZEROLENGTH_WRITEPROTECTED:
		strText = StrFormat("Unsupported zero-length write-protected file: %s.",
							pszImageFilename);
		break;

	case eIMAGE_ERROR_FAILED_TO_INIT_ZEROLENGTH:
		strText = StrFormat("Failed to resize the zero-length file: %s.",
							pszImageFilename);
		break;

	default:
		// IGNORE OTHER ERRORS SILENTLY
		return;
	}

	GetFrame().FrameMessageBox(strText.c_str(),
							   g_pAppTitle.c_str(),
							   MB_ICONEXCLAMATION | MB_SETFOREGROUND);
}

//===========================================================================

bool Disk2InterfaceCard::GetProtect(const int drive)
{
	if (!IsDriveValid(drive))
		return true;

	return m_floppyDrive[drive].m_disk.m_bWriteProtected;
}

//===========================================================================

void Disk2InterfaceCard::SetProtect(const int drive, const bool bWriteProtect)
{
	if (!IsDriveValid(drive))
		return;

	m_floppyDrive[drive].m_disk.m_bWriteProtected = bWriteProtect;
}

//===========================================================================

bool Disk2InterfaceCard::IsDriveEmpty(const int drive)
{
	if (!IsDriveValid(drive))
		return true;

	return m_floppyDrive[drive].m_disk.m_imagehandle == NULL;
}

//===========================================================================

bool Disk2InterfaceCard::IsWozImageInDrive(const int drive)
{
	if (!IsDriveValid(drive))
		return false;

	return ImageIsWOZ(m_floppyDrive[drive].m_disk.m_imagehandle);
}

//===========================================================================

#if LOG_DISK_NIBBLES_WRITE
bool Disk2InterfaceCard::LogWriteCheckSyncFF(ULONG& uCycleDelta)
{
	bool bIsSyncFF = false;

	if (m_uWriteLastCycle == 0)	// Reset to 0 when write mode is enabled
	{
		uCycleDelta = 0;
		if (m_floppyLatch == 0xFF)
		{
			m_uSyncFFCount = 0;
			bIsSyncFF = true;
		}
	}
	else
	{
		uCycleDelta = (ULONG) (g_nCumulativeCycles - m_uWriteLastCycle);
		if (m_floppyLatch == 0xFF && uCycleDelta > 32)
		{
			m_uSyncFFCount++;
			bIsSyncFF = true;
		}
	}

	m_uWriteLastCycle = g_nCumulativeCycles;
	return bIsSyncFF;
}
#endif

//===========================================================================

void Disk2InterfaceCard::UpdateLatchForEmptyDrive(FloppyDrive* pDrive)
{
	if (!pDrive->m_isConnected)
	{
		m_floppyLatch = 0x80;	// GH#864
		return;
	}

	// Drive connected

	if ((g_nCumulativeCycles - pDrive->m_motorOnCycle) < MOTOR_ON_UNTIL_LSS_STABLE_CYCLES)
		m_floppyLatch = 0x80;	// GH#864
	else
		m_floppyLatch = rand() & 0xFF;	// GH#748
}

void __stdcall Disk2InterfaceCard::ReadWrite(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULONG uExecutedCycles)
{
	FloppyDrive* pDrive = &m_floppyDrive[m_currDrive];
	FloppyDisk* pFloppy = &pDrive->m_disk;

	if (!pFloppy->m_trackimagedata && pFloppy->m_imagehandle)
		ReadTrack(m_currDrive, uExecutedCycles);

	if (!pFloppy->m_trackimagedata)
		return UpdateLatchForEmptyDrive(pDrive);

	// Improve precision of "authentic" drive mode - GH#125
	UINT uSpinNibbleCount = 0;

	if (!m_enhanceDisk && pDrive->m_spinning)
	{
		const ULONG nCycleDiff = (ULONG) (g_nCumulativeCycles - m_diskLastCycle);
		m_diskLastCycle = g_nCumulativeCycles;

		if (nCycleDiff > 40)
		{
			// 40 cycles for a write of a 10-bit 0xFF sync byte
			uSpinNibbleCount = nCycleDiff >> 5;	// ...but divide by 32 (not 40)

			ULONG uWrapOffset = uSpinNibbleCount % pFloppy->m_nibbles;
			pFloppy->m_byte += uWrapOffset;
			if (pFloppy->m_byte >= pFloppy->m_nibbles)
				pFloppy->m_byte -= pFloppy->m_nibbles;

#if LOG_DISK_NIBBLES_SPIN
			UINT uCompleteRevolutions = uSpinNibbleCount / pFloppy->m_nibbles;
			LOG_DISK("spin: revs=%d, nibbles=%d\r\n", uCompleteRevolutions, uWrapOffset);
#endif
		}
	}

	if (!m_seqFunc.writeMode)
	{
		// Don't change latch if drive off after 1 second drive-off delay (UTAIIe page 9-13)
		// "DRIVES OFF forces the data register to hold its present state." (UTAIIe page 9-12)
		// Note: Sherwood Forest sets shift mode and reads with the drive off.
		if (!pDrive->m_spinning)	// GH#599
			return;

		const ULONG nReadCycleDiff = (ULONG) (g_nCumulativeCycles - m_diskLastReadLatchCycle);

		// Support partial nibble read if disk reads are very close: (GH#582)
		// . 6 cycles (1st->2nd read) for DOS 3.3 / $BD34: "read with delays to see if disk is spinning." (Beneath Apple DOS)
		// . 6 cycles (1st->2nd read) for Curse of the Azure Bonds (loop to see if disk is spinning)
		// . 25 cycles or higher fails for Legacy of the Ancients (GH#733)
		// . 31 cycles is the max for a partial 8-bit nibble
		const ULONG kReadAccessThreshold = 6;	// Same for enhanced/authentic modes

		if (nReadCycleDiff <= kReadAccessThreshold)
		{
			UINT invalidBits = 8 - (nReadCycleDiff / 4);	// 4 cycles per bit-cell
			m_floppyLatch = *(pFloppy->m_trackimage + pFloppy->m_byte) >> invalidBits;
			return;	// Early return so don't update: m_diskLastReadLatchCycle & pFloppy->byte
		}

		m_floppyLatch = *(pFloppy->m_trackimage + pFloppy->m_byte);
		m_diskLastReadLatchCycle = g_nCumulativeCycles;

#if LOG_DISK_NIBBLES_READ
  #if LOG_DISK_NIBBLES_USE_RUNTIME_VAR
		if (m_bLogDisk_NibblesRW)
  #endif
		{
			LOG_DISK("read %04X = %02X\r\n", pFloppy->m_byte, m_floppyLatch);
		}

		m_formatTrack.DecodeLatchNibbleRead(m_floppyLatch);
#endif
	}
	else if (!pFloppy->m_bWriteProtected) // && m_seqFunc.writeMode
	{
		if (!pDrive->m_spinning)
			return;		// If not spinning then only 1 bit-cell gets written?

		*(pFloppy->m_trackimage + pFloppy->m_byte) = m_floppyLatch;
		pFloppy->m_trackimagedirty = true;

		bool bIsSyncFF = false;
#if LOG_DISK_NIBBLES_WRITE
		ULONG uCycleDelta = 0;
		bIsSyncFF = LogWriteCheckSyncFF(uCycleDelta);
#endif

		m_formatTrack.DecodeLatchNibbleWrite(m_floppyLatch, uSpinNibbleCount, pFloppy, bIsSyncFF);	// GH#125

#if LOG_DISK_NIBBLES_WRITE
  #if LOG_DISK_NIBBLES_USE_RUNTIME_VAR
		if (m_bLogDisk_NibblesRW)
  #endif
		{
			if (!bIsSyncFF)
				LOG_DISK("write %04X = %02X (cy=+%d)\r\n", pFloppy->m_byte, m_floppyLatch, uCycleDelta);
			else
				LOG_DISK("write %04X = %02X (cy=+%d) sync #%d\r\n", pFloppy->m_byte, m_floppyLatch, uCycleDelta, m_uSyncFFCount);
		}
#endif
	}

	// GH #1212 We have a non .WOZ disk, mirror so that GetCurrentShiftReg() returns last nibble read
	m_shiftReg = m_floppyLatch;

	if (++pFloppy->m_byte >= pFloppy->m_nibbles)
		pFloppy->m_byte = 0;

	// Show track status (GH#201) - NB. Prevent flooding of forcing UI to redraw!!!
	if ((pFloppy->m_byte & 0xFF) == 0)
		GetFrame().FrameDrawDiskStatus();
}

//===========================================================================

void Disk2InterfaceCard::ResetLogicStateSequencer(void)
{
	m_shiftReg = 0;
	m_latchDelay = 0;
	m_writeStarted = false;
	m_dbgLatchDelayedCnt = 0;

	m_T00S00PatternIdx = 0;
	m_foundT00S00Pattern = false;
}

UINT Disk2InterfaceCard::GetBitCellDelta(const ULONG uExecutedCycles)
{
	FloppyDisk& floppy = m_floppyDrive[m_currDrive].m_disk;

	const BYTE optimalBitTiming = ImageGetOptimalBitTiming(floppy.m_imagehandle);

	// NB. m_extraCycles is needed to retain accuracy:
	// . Read latch #1: 0-> 9: cycleDelta= 9, bitCellDelta=2, extraCycles=1
	// . Read latch #2: 9->20: cycleDelta=11, bitCellDelta=2, extraCycles=3
	// . Overall:       0->20: cycleDelta=20, bitCellDelta=5, extraCycles=0
	UINT bitCellDelta;
#if 0
	if (optimalBitTiming == 32)
	{
		const ULONG cycleDelta = (ULONG)(g_nCumulativeCycles - m_diskLastCycle) + (BYTE) floppy.m_extraCycles;
		bitCellDelta = cycleDelta / 4;	// DIV 4 for 4us per bit-cell
		floppy.m_extraCycles = cycleDelta & 3;	// MOD 4 : remainder carried forward for next time
	}
	else
#endif
	{
		const double cycleDelta = (double)(g_nCumulativeCycles - m_diskLastCycle) + floppy.m_extraCycles;
		const double bitTime = 0.125 * (double)optimalBitTiming;	// 125ns units
		bitCellDelta = (UINT) floor( cycleDelta / bitTime );
		floppy.m_extraCycles = (double)cycleDelta - ((double)bitCellDelta * bitTime);
	}

	// NB. actual m_diskLastCycle for the last bitCell is minus floppy.m_extraCycles
	// - but don't need this value; and it's correctly accounted for in this function.
	m_diskLastCycle = g_nCumulativeCycles;

	return bitCellDelta;
}

void Disk2InterfaceCard::UpdateBitStreamPosition(FloppyDisk& floppy, const ULONG bitCellDelta)
{
	if (floppy.m_bitCount == 0)	// Repro: Boot DOS3.3(WOZ), eject+reinsert disk, CALL-151, C0E9 N C0ED ; motor-on & LoadWriteProtect()
		return;

	floppy.m_bitOffset += bitCellDelta;
	if (floppy.m_bitOffset >= floppy.m_bitCount)
		floppy.m_bitOffset %= floppy.m_bitCount;

	UpdateBitStreamOffsets(floppy);
}

void Disk2InterfaceCard::UpdateBitStreamOffsets(FloppyDisk& floppy)
{
	floppy.m_byte = floppy.m_bitOffset / 8;
	const UINT remainder = 7 - (floppy.m_bitOffset & 7);
	floppy.m_bitMask = 1 << remainder;
}

__forceinline void Disk2InterfaceCard::IncBitStream(FloppyDisk& floppy)
{
	floppy.m_bitMask >>= 1;
	if (!floppy.m_bitMask)
	{
		floppy.m_bitMask = 1 << 7;
		floppy.m_byte++;
	}

	floppy.m_bitOffset++;
	if (floppy.m_bitOffset == floppy.m_bitCount)
	{
		floppy.m_bitMask = 1 << 7;
		floppy.m_bitOffset = 0;
		floppy.m_byte = 0;
	}

	if (floppy.m_bitOffset == floppy.m_initialBitOffset)
		floppy.m_revs++;
}

void Disk2InterfaceCard::PreJitterCheck(int phase, BYTE latch)
{
	if (phase != 0 || (latch & 0x80) == 0)
		return;

	if (latch == m_T00S00Pattern[m_T00S00PatternIdx])
	{
		m_T00S00PatternIdx++;
		if (m_T00S00PatternIdx == sizeof(m_T00S00Pattern))
			m_foundT00S00Pattern = true;	// 6502 code has just read latch nibbles for T$00,S$00 address prologue
	}
	else
	{
		m_T00S00PatternIdx = 0;
	}
}

// GH#930: After T$00,S$00 randomly skip 1 bit-cell.
// . PreJitterCheck() condition met && skipped a big number of bit-cells.
// . Fix is just for 'Wasteland' and 'Legacy of the Ancients' (but shouldn't interfere with any other woz images).
// . NB. This is likely to be the transition from DiskII firmware ($C6xx) to user-code ($801),
//   so skipping 1 bit-cell here shouldn't matter.
// . And (see comment [*1]) the T00S00 pattern only matches a handful of titles.
void Disk2InterfaceCard::AddJitter(int phase, FloppyDisk& floppy)
{
	if (phase == 0 && m_foundT00S00Pattern)
	{
		if (rand() < RAND_THRESHOLD(1, 10))
		{
			LogOutput("Disk: T$00 jitter - slip 1 bitcell (PC=%04X)\n", regs.pc);
			IncBitStream(floppy);
		}
		else
		{
			LogOutput("Disk: T$00 jitter - ***  SKIP  *** (PC=%04X)\n", regs.pc);
		}
	}

	m_T00S00PatternIdx = 0;
	m_foundT00S00Pattern = false;
}

// GH#1125: For T$21 (track 33.0) or above (and sufficiently long sync FF/10 run-length), then randomly skip 1 bit-cell at the start of the FF/2 track seam.
// Example of high sync FF/10 run-lengths for tracks 33.0+:
// . Accolade Comics:114, Silent Service:117, Wings of Fury:140, Wizardry I:127, Wizardry III:283
// NB. Restrict to higher FF/10 run-lengths to limit the titles affected by this jitter.
void Disk2InterfaceCard::AddTrackSeamJitter(float phasePrecise, FloppyDisk& floppy)
{
	if (phasePrecise >= (33.0 * 2) && floppy.m_longestSyncFFRunLength > 110)
	{
		if (floppy.m_bitOffset == floppy.m_longestSyncFFBitOffsetStart)
		{
			if (rand() < RAND_THRESHOLD(5, 10))
			{
				LogOutput("Disk: T%05.2f jitter - slip 1 bitcell  (revs=%d) (PC=%04X)\n", phasePrecise / 2, floppy.m_revs, regs.pc);
				IncBitStream(floppy);
			}
			else
			{
				LogOutput("Disk: T%05.2f jitter - ***  SKIP  ***  (revs=%d) (PC=%04X)\n", phasePrecise / 2, floppy.m_revs, regs.pc);
			}
		}
	}
}

void __stdcall Disk2InterfaceCard::DataLatchReadWriteWOZ(WORD pc, WORD addr, BYTE bWrite, ULONG uExecutedCycles)
{
	_ASSERT(m_seqFunc.function != dataShiftWrite);

	FloppyDrive& drive = m_floppyDrive[m_currDrive];
	FloppyDisk& floppy = drive.m_disk;

	if (!floppy.m_trackimagedata && floppy.m_imagehandle)
	{
		ReadTrack(m_currDrive, uExecutedCycles);
		// NB. ReadTrack() has called GetBitCellDelta(), so the subsequent call to GetBitCellDelta() below just returns bitCellDelta==0
		// So could just return at this point.
	}

	if (!floppy.m_trackimagedata)
	{
		_ASSERT(0);		// Can't happen for WOZ - ReadTrack() should return an empty track
		return UpdateLatchForEmptyDrive(&drive);
	}

	// Don't change latch if drive off after 1 second drive-off delay (UTAIIe page 9-13)
	// "DRIVES OFF forces the data register to hold its present state." (UTAIIe page 9-12)
	// Note: Sherwood Forest sets shift mode and reads with the drive off.
	// TODO: And same for a write?
	if (!drive.m_spinning)	// GH#599
		return;

	// Skipping forward a large amount of bitcells means the bitstream will very likely be out-of-sync.
	// The first 1-bit will produce a latch nibble, and this 1-bit is unlikely to be the nibble's high bit.
	// So we need to ensure we run enough bits through the sequencer to re-sync.
	const UINT significantBitCells = 100;	// eg. long stream of weak bits and/or 5x 10-bit sync FF nibbles (GH#1020)
	UINT bitCellDelta = GetBitCellDelta(uExecutedCycles);

	UINT bitCellRemainder;
	if (bitCellDelta <= significantBitCells)
	{
		bitCellRemainder = bitCellDelta;
	}
	else
	{
		bitCellRemainder = significantBitCells;
		bitCellDelta -= significantBitCells;

		UpdateBitStreamPosition(floppy, bitCellDelta);

		m_latchDelay = 0;
		drive.m_headWindow = 0;

		AddJitter(drive.m_phase, floppy);	// Only call when skipping a big number of bit-cells (ie. >significantBitCells)
	}

	if (!bWrite)
	{
		if (m_seqFunc.function != readSequencing)
		{
			_ASSERT(m_seqFunc.function == checkWriteProtAndInitWrite);
			UpdateBitStreamPosition(floppy, bitCellRemainder);
			return;
		}

		DataLatchReadWOZ(pc, addr, bitCellRemainder);

		PreJitterCheck(drive.m_phase, m_floppyLatch);	// Pre: m_floppyLatch just updated
	}
	else
	{
		_ASSERT(m_seqFunc.function == dataLoadWrite);
		DataLoadWriteWOZ(pc, addr, bitCellRemainder);
	}

	// Show track status (GH#201) - NB. Prevent flooding of forcing UI to redraw!!!
	if ((floppy.m_byte & 0xFF) == 0)
		GetFrame().FrameDrawDiskStatus();
}

void Disk2InterfaceCard::DataLatchReadWOZ(WORD pc, WORD addr, UINT bitCellRemainder)
{
	// m_diskLastReadLatchCycle = g_nCumulativeCycles;	// Not used by WOZ (only by NIB)

#if LOG_DISK_NIBBLES_READ
	bool newLatchData = false;
#endif

	FloppyDrive& drive = m_floppyDrive[m_currDrive];
	FloppyDisk& floppy = drive.m_disk;

#if _DEBUG
	static int dbgWOZ = 0;
	if (dbgWOZ)
	{
		dbgWOZ = 0;
		DumpTrackWOZ(floppy);	// Enable as necessary
	}
#endif

	for (UINT i = 0; i < bitCellRemainder; i++)
	{
		BYTE n = floppy.m_trackimage[floppy.m_byte];

		drive.m_headWindow <<= 1;
		drive.m_headWindow |= (n & floppy.m_bitMask) ? 1 : 0;
		BYTE outputBit = (drive.m_headWindow & 0xf)	? (drive.m_headWindow >> 1) & 1
													: (rand() < RAND_THRESHOLD(3, 10)) ? 1 : 0;	// ~30% chance of a 1 bit (Ref: WOZ-2.0)

		IncBitStream(floppy);

		AddTrackSeamJitter(drive.m_phasePrecise, floppy);

		m_shiftReg <<= 1;
		m_shiftReg |= outputBit;

		if (m_latchDelay)
		{
			m_latchDelay -= 4;
			if (m_latchDelay < 0)
				m_latchDelay = 0;

			if (m_shiftReg)
			{
				m_dbgLatchDelayedCnt = 0;
			}
			else // m_shiftReg==0
			{
				m_latchDelay += 4;	// extend by 4us (so 7us again) - GH#662

				m_dbgLatchDelayedCnt++;
#if LOG_DISK_NIBBLES_READ
				if (m_dbgLatchDelayedCnt >= 3)
				{
					LOG_DISK("read: latch held due to 0: PC=%04X, cnt=%02X\r\n", regs.pc, m_dbgLatchDelayedCnt);
				}
#endif
			}
		}

		if (!m_latchDelay)
		{
#if LOG_DISK_NIBBLES_READ
			if (newLatchData)
			{
				LOG_DISK("read skipped latch data: %04X = %02X\r\n", floppy.m_byte, m_floppyLatch);
				newLatchData = false;
			}
#endif
			m_floppyLatch = m_shiftReg;

			if (m_shiftReg & 0x80)
			{
				m_latchDelay = 7;
				m_shiftReg = 0;
#if LOG_DISK_NIBBLES_READ
				// May not actually be read by 6502 (eg. Prologue's CHKSUM 4&4 nibble pair), but still pass to the log's nibble reader
				m_formatTrack.DecodeLatchNibbleRead(m_floppyLatch);
				newLatchData = true;
#endif
			}
		}
	} // for

#if LOG_DISK_NIBBLES_READ
	if (m_floppyLatch & 0x80)
	{
#if LOG_DISK_NIBBLES_USE_RUNTIME_VAR
		if (m_bLogDisk_NibblesRW)
#endif
		{
			LOG_DISK("read %04X = %02X\r\n", floppy.m_byte, m_floppyLatch);
		}
	}
#endif
}

void Disk2InterfaceCard::DataLoadWriteWOZ(WORD pc, WORD addr, UINT bitCellRemainder)
{
	_ASSERT(m_seqFunc.function == dataLoadWrite);

	FloppyDrive& drive = m_floppyDrive[m_currDrive];
	FloppyDisk& floppy = drive.m_disk;

	if (floppy.m_bWriteProtected)
	{
		_ASSERT(0);	// Must be a bug in the 6502 code for this to occur!
		UpdateBitStreamPosition(floppy, bitCellRemainder);
		return;
	}

	if (!m_writeStarted)
		UpdateBitStreamPosition(floppy, bitCellRemainder);	// skip over bitCells before switching to write mode

	m_writeStarted = true;
#if LOG_DISK_WOZ_LOADWRITE
	LOG_DISK("load shiftReg with %02X (was: %02X)\n", m_floppyLatch, m_shiftReg);
#endif
	m_shiftReg = m_floppyLatch;

	floppy.m_longestSyncFFBitOffsetStart = -1;	// invalidate the track seam location after a write
}

void Disk2InterfaceCard::DataShiftWriteWOZ(WORD pc, WORD addr, ULONG uExecutedCycles)
{
	_ASSERT(m_seqFunc.function == dataShiftWrite);

	FloppyDrive& drive = m_floppyDrive[m_currDrive];
	FloppyDisk& floppy = drive.m_disk;

	const UINT bitCellRemainder = GetBitCellDelta(uExecutedCycles);

	if (floppy.m_bWriteProtected)
	{
		_ASSERT(0);	// Must be a bug in the 6502 code for this to occur!
		UpdateBitStreamPosition(floppy, bitCellRemainder);
		return;
	}

	if (!drive.m_spinning)
		return;

	if (!floppy.m_trackimagedata)	// GH#1126
		return;

#if LOG_DISK_WOZ_SHIFTWRITE
	LOG_DISK("T$%02X, bitOffset=%04X: %02X (%d bits)\n", drive.m_phase/2, floppy.m_bitOffset, m_shiftReg, bitCellRemainder);
#endif

	for (UINT i = 0; i < bitCellRemainder; i++)
	{
		BYTE outputBit = m_shiftReg & 0x80;
		m_shiftReg <<= 1;

		BYTE n = floppy.m_trackimage[floppy.m_byte];
		n &= ~floppy.m_bitMask;
		if (outputBit) n |= floppy.m_bitMask;
		floppy.m_trackimage[floppy.m_byte] = n;

		IncBitStream(floppy);
	}

	floppy.m_trackimagedirty = true;
}

//===========================================================================

// For now all that's needed is this basic case:
// . find [start,end] of longest run of FF/10 sync nibbles
void Disk2InterfaceCard::FindTrackSeamWOZ(FloppyDisk& floppy, float track)
{
	const UINT oldBitOffset = floppy.m_bitOffset;	// Save current state

	BYTE shiftReg = 0;
	UINT zeroCount = 0;

	int startBitOffset = -1;	// NB. change this to start of first FF/10
	floppy.m_bitOffset = 0;
	UpdateBitStreamOffsets(floppy);

	int nibbleStartBitOffset = -1;
	int syncFFStartBitOffset = -1;
	int syncFFRunLength = 0;
	int longestSyncFFStartBitOffset = -1;
	int longestSyncFFRunLength = 0;

	floppy.m_longestSyncFFBitOffsetStart = -1;

	while (1)
	{
		BYTE n = floppy.m_trackimage[floppy.m_byte];
		BYTE outputBit = (n & floppy.m_bitMask) ? 1 : 0;

		IncBitStream(floppy);

		if ((startBitOffset < 0 && floppy.m_bitOffset == 0) || (startBitOffset == floppy.m_bitOffset))	// done complete track?
			break;

		if (shiftReg & 0x80)
		{
			if (outputBit == 0)		// zero, so LSS holds nibble in latch
			{
				zeroCount++;
				continue;
			}

			// else: start of next nibble

			if (shiftReg == 0xff && zeroCount == 2)
			{
				if (syncFFStartBitOffset < 0)
					syncFFStartBitOffset = nibbleStartBitOffset;
				syncFFRunLength++;
			}

			if ((shiftReg != 0xff || zeroCount != 2) && syncFFStartBitOffset >= 0)
			{
				// Longest FF/2 run could straddle end/start of track's bit buffer
				if (startBitOffset < 0)
					startBitOffset = nibbleStartBitOffset;

				if (longestSyncFFRunLength < syncFFRunLength)
				{
					longestSyncFFStartBitOffset = syncFFStartBitOffset;
					longestSyncFFRunLength = syncFFRunLength;
				}
				syncFFStartBitOffset = -1;
				syncFFRunLength = 0;
			}

			shiftReg = 0;
			zeroCount = 0;
		}

		shiftReg <<= 1;
		shiftReg |= outputBit;

		if (shiftReg == 0x01)
		{
			nibbleStartBitOffset = floppy.m_bitOffset - 1;
			if (nibbleStartBitOffset < 0) nibbleStartBitOffset += floppy.m_bitCount;
		}
	}

	if (longestSyncFFRunLength)
	{
		const int longestSyncFFBitOffsetEnd = (longestSyncFFStartBitOffset + longestSyncFFRunLength * 10 - 1) % floppy.m_bitCount;
#if LOG_DISK_WOZ_TRACK_SEAM
		LOG_DISK("Track seam: T%05.2f: FF/10 (run=%d), start=%04X, end=%04X\n", track, longestSyncFFRunLength, longestSyncFFStartBitOffset, longestSyncFFBitOffsetEnd);
#endif
		floppy.m_longestSyncFFBitOffsetStart = longestSyncFFStartBitOffset;
		floppy.m_longestSyncFFRunLength = longestSyncFFRunLength;
	}
	else
	{
#if LOG_DISK_WOZ_TRACK_SEAM
		LOG_DISK("Track seam: T%05.2f: FF/10 (none)\n", track);
#endif
	}

	// Restore state

	floppy.m_bitOffset = oldBitOffset;
	UpdateBitStreamOffsets(floppy);
}

//===========================================================================

#ifdef _DEBUG
// Dump nibbles from current position bitstream wraps to same position
// NB. Need to define LOG_DISK_NIBBLES_READ so that GetReadD5AAxxDetectedString() works.
void Disk2InterfaceCard::DumpTrackWOZ(FloppyDisk floppy)	// pass a copy of m_floppy
{
	FormatTrack formatTrack(true);

	BYTE shiftReg = 0;
	UINT zeroCount = 0;
	UINT nibbleCount = 0;

	const UINT startBitOffset = 0;	// NB. may need to tweak this offset, since the bitstream is a circular buffer
	floppy.m_bitOffset = startBitOffset;
	UpdateBitStreamOffsets(floppy);

	int nibbleStartBitOffset = -1;

	bool newLine = true;
	bool doneLastBit = false;

	while (1)
	{
		if (newLine && nibbleStartBitOffset >= 0)
		{
			newLine = false;
			LogOutput("%04X:", nibbleStartBitOffset);
			nibbleStartBitOffset = -1;
		}

		BYTE n = floppy.m_trackimage[floppy.m_byte];
		BYTE outputBit = (n & floppy.m_bitMask) ? 1 : 0;

		IncBitStream(floppy);

		if (startBitOffset == floppy.m_bitOffset)	// done complete track?
			doneLastBit = true;
		else if (doneLastBit)
			break;

		if (shiftReg & 0x80)
		{
			if (outputBit == 0)		// zero, so LSS holds nibble in latch
			{
				zeroCount++;
				continue;
			}

			// else: start of next nibble

			nibbleCount++;

			char syncBits = zeroCount <= 9 ? '0' + zeroCount : '+';
			if (zeroCount == 0)	LogOutput("%02X   ", shiftReg);
			else				LogOutput("%02X(%c)", shiftReg, syncBits);

			formatTrack.DecodeLatchNibbleRead(shiftReg);

			if ((nibbleCount % 32) == 0)
			{
				std::string strReadDetected = formatTrack.GetReadD5AAxxDetectedString();
				if (!strReadDetected.empty())
				{
					OutputDebugString("\t; ");
					OutputDebugString(strReadDetected.c_str());
				}
				OutputDebugString("\n");
				newLine = true;
			}

			shiftReg = 0;
			zeroCount = 0;
		}

		shiftReg <<= 1;
		shiftReg |= outputBit;

		if (shiftReg == 0x01)
		{
			nibbleStartBitOffset = floppy.m_bitOffset - 1;
			if (nibbleStartBitOffset < 0) nibbleStartBitOffset += floppy.m_bitCount;
		}
	}

	// Output any partial nibble
	if (shiftReg & 0x80)
	{
		LogOutput("%02X", shiftReg);

		// Output any remaining zeroCount
		if (zeroCount)
		{
			char syncBits = zeroCount <= 9 ? '0' + zeroCount : '+';
			LogOutput("(%c)", syncBits);
		}
	}
	else if (shiftReg)
	{
		LogOutput("%02X/Partial Nibble", shiftReg);
	}

	// Output any remaining "read D5AAxx detected"
	if (nibbleCount % 32)
	{
		std::string strReadDetected = formatTrack.GetReadD5AAxxDetectedString();
		if (!strReadDetected.empty())
		{
			OutputDebugString("\t; ");
			OutputDebugString(strReadDetected.c_str());
		}
		OutputDebugString("\n");
	}
}
#endif

//===========================================================================

void Disk2InterfaceCard::Reset(const bool bIsPowerCycle)
{
	// RESET forces all switches off (UTAIIe Table 9.1)
	ResetSwitches();

	m_formatTrack.Reset();

	ResetLogicStateSequencer();

	if (bIsPowerCycle)	// GH#460
	{
		// NB. This doesn't affect the drive head (ie. drive's track position)
		// . The initial machine start-up state is track=0, but after a power-cycle the track could be any value.
		// . (For DiskII firmware, this results in a subtle extra latch read in this latter case, for the track!=0 case)

		m_floppyDrive[DRIVE_1].m_spinning   = 0;
		m_floppyDrive[DRIVE_1].m_writelight = 0;
		m_floppyDrive[DRIVE_2].m_spinning   = 0;
		m_floppyDrive[DRIVE_2].m_writelight = 0;

		GetFrame().FrameRefreshStatus(DRAW_LEDS);
	}

	InitFirmware(GetCxRomPeripheral());
	GetFrame().FrameRefreshStatus(DRAW_TITLE);
}

void Disk2InterfaceCard::ResetSwitches(void)
{
	m_currDrive = 0;
	m_floppyMotorOn = 0;
	m_magnetStates = 0;
	m_seqFunc.function = readSequencing;
}

//===========================================================================

bool Disk2InterfaceCard::UserSelectNewDiskImage(const int drive, LPCSTR pszFilename/*=""*/)
{
	if (!IsDriveConnected(drive))
	{
		GetFrame().FrameMessageBox("Drive not connected!", "Insert disk", MB_ICONEXCLAMATION|MB_SETFOREGROUND|MB_OK);
		return false;
	}

	TCHAR directory[MAX_PATH];
	TCHAR filename[MAX_PATH];

	StringCbCopy(filename, MAX_PATH, pszFilename);

	RegLoadString(TEXT(REG_PREFS), TEXT(REGVALUE_PREF_START_DIR), 1, directory, MAX_PATH, TEXT(""));
	std::string title = StrFormat("Select Disk Image For Drive %d", drive + 1);

	OPENFILENAME ofn;
	memset(&ofn, 0, sizeof(OPENFILENAME));
	ofn.lStructSize     = sizeof(OPENFILENAME);
	ofn.hwndOwner       = GetFrame().g_hFrameWindow;
	ofn.hInstance       = GetFrame().g_hInstance;
	ofn.lpstrFilter     = TEXT("All Images\0*.bin;*.do;*.dsk;*.nib;*.po;*.gz;*.woz;*.zip;*.2mg;*.2img;*.iie;*.apl\0")
						  TEXT("Disk Images (*.bin,*.do,*.dsk,*.nib,*.po,*.gz,*.woz,*.zip,*.2mg,*.2img,*.iie)\0*.bin;*.do;*.dsk;*.nib;*.po;*.gz;*.woz;*.zip;*.2mg;*.2img;*.iie\0")
						  TEXT("All Files\0*.*\0");
	ofn.lpstrFile       = filename;
	ofn.nMaxFile        = MAX_PATH;
	ofn.lpstrInitialDir = directory;
	ofn.Flags           = OFN_PATHMUSTEXIST;
	ofn.lpstrTitle      = title.c_str();

	bool bRes = false;

	if (GetOpenFileName(&ofn))
	{
		std::string openFilename = filename;
		if ((!ofn.nFileExtension) || !filename[ofn.nFileExtension])
			openFilename += TEXT(".dsk");

		ImageError_e Error = InsertDisk(drive, openFilename, ofn.Flags & OFN_READONLY, IMAGE_CREATE);
		if (Error == eIMAGE_ERROR_NONE)
		{
			bRes = true;
		}
		else
		{
			NotifyInvalidImage(drive, openFilename, Error);
		}
	}

	return bRes;
}

//===========================================================================

void __stdcall Disk2InterfaceCard::LoadWriteProtect(WORD, WORD, BYTE write, BYTE value, ULONG uExecutedCycles)
{
	// Don't change latch if drive off after 1 second drive-off delay (UTAIIe page 9-13)
	// "DRIVES OFF forces the data register to hold its present state." (UTAIIe page 9-12)
	// Note: Gemstone Warrior sets load mode with the drive off.
	if (!m_floppyDrive[m_currDrive].m_spinning)	// GH#599
		return;

	// Notes:
	// . Only READ-LOAD mode ($C08E,X & $C08D,X) can issue the SR (shift write-protect) operation - UTAIIe page 9-20, fig 9.11
	// . Phase 1 on also forces write protect in the Disk II drive (UTAIIe page 9-7) but we don't implement that.
	// . write mode doesn't prevent reading write protect (GH#537):
	//   "If for some reason the above write protect check were entered with the READ/WRITE switch in WRITE, 
	//    the write protect switch would still be read correctly" (UTAIIe page 9-21)
	// . Sequencer "SR" (Shift Right) command shifts the data register right and loads QA (bit7) with write protect (UTAIIe page 9-21)
	// . A read or write will shift 'write protect' in QA.
	// . The LSS saturates the data register before the CPU can read an intermediate value: so set to 0xFF or 0x00 (GH#1078)
	FloppyDisk& floppy = m_floppyDrive[m_currDrive].m_disk;
	if (floppy.m_bWriteProtected)
		m_floppyLatch = 0xFF;
	else
		m_floppyLatch = 0x00;

	if (m_writeStarted)	// Prevent ResetLogicStateSequencer() from resetting m_writeStarted
		return;

	if (ImageIsWOZ(floppy.m_imagehandle))
	{
#if LOG_DISK_NIBBLES_READ
		LOG_DISK("%08X: reset LSS: ~PC=%04X\r\n", (UINT32)g_nCumulativeCycles, regs.pc);
#endif

		const UINT bitCellDelta = GetBitCellDelta(uExecutedCycles);
		UpdateBitStreamPosition(floppy, bitCellDelta);	// Fix E7-copy protection

		ResetLogicStateSequencer();	// "Set the sequencer to State 0" (UTAIIe page 9-21)
	}
}

//===========================================================================

void __stdcall Disk2InterfaceCard::SetReadMode(WORD, WORD, BYTE, BYTE, ULONG uExecutedCycles)
{
	m_formatTrack.DriveSwitchedToReadMode(&m_floppyDrive[m_currDrive].m_disk);

#if LOG_DISK_RW_MODE
	LOG_DISK("%08X: rw mode: read\r\n", (UINT32)g_nCumulativeCycles);
#endif
}

//===========================================================================

void __stdcall Disk2InterfaceCard::SetWriteMode(WORD, WORD, BYTE, BYTE, ULONG uExecutedCycles)
{
	m_formatTrack.DriveSwitchedToWriteMode(m_floppyDrive[m_currDrive].m_disk.m_byte);

	BOOL modechange = !m_floppyDrive[m_currDrive].m_writelight;
#if LOG_DISK_RW_MODE
	LOG_DISK("rw mode: write (mode changed=%d)\r\n", modechange ? 1 : 0);
#endif
#if LOG_DISK_NIBBLES_WRITE
	m_uWriteLastCycle = 0;
#endif

	m_floppyDrive[m_currDrive].m_writelight = WRITELIGHT_CYCLES;

	if (modechange)
		GetFrame().FrameDrawDiskLEDS();
}

//===========================================================================

void Disk2InterfaceCard::Update(const ULONG cycles)
{
	int loop = NUM_DRIVES;
	while (loop--)
	{
		FloppyDrive* pDrive = &m_floppyDrive[loop];

		if (pDrive->m_spinning && !m_floppyMotorOn)
		{
			if (!(pDrive->m_spinning -= MIN(pDrive->m_spinning, cycles)))
			{
				GetFrame().FrameDrawDiskLEDS();
				GetFrame().FrameDrawDiskStatus();
			}
		}

		if (m_seqFunc.writeMode && (m_currDrive == loop) && pDrive->m_spinning)
		{
			pDrive->m_writelight = WRITELIGHT_CYCLES;
		}
		else if (pDrive->m_writelight)
		{
			if (!(pDrive->m_writelight -= MIN(pDrive->m_writelight, cycles)))
			{
				GetFrame().FrameDrawDiskLEDS();
				GetFrame().FrameDrawDiskStatus();
			}
		}
	}
}

//===========================================================================

bool Disk2InterfaceCard::DriveSwap(void)
{
	// Refuse to swap if either Disk][ is active
	// TODO: if Shift-Click then FORCE drive swap to bypass message
	if (m_floppyDrive[DRIVE_1].m_spinning || m_floppyDrive[DRIVE_2].m_spinning)
	{
		// 1.26.2.4 Prompt when trying to swap disks while drive is on instead of silently failing
		int status = GetFrame().FrameMessageBox(
			"WARNING:\n"
				"\n"
				"\tAttempting to swap a disk while a drive is on\n"
				"\t\t--> is NOT recommended <--\n"
				"\tas this will most likely read/write incorrect data!\n"
				"\n"
				"If the other drive is empty then swapping is harmless. The"
				" computer will appear to 'hang' trying to read non-existent data but"
				" you can safely swap disks once more to restore the original disk.\n"
				"\n"
				"Do you still wish to swap disks?",
			"Trying to swap a disk while a drive is on ...",
			MB_ICONWARNING | MB_YESNOCANCEL
		);

		switch( status )
		{
			case IDNO:
			case IDCANCEL:
				return false;
			default:
				break; // User is OK with swapping disks so let them proceed at their own risk
		}
	}

	FlushCurrentTrack(DRIVE_1);
	FlushCurrentTrack(DRIVE_2);

	// Swap disks between drives
	// . NB. We swap trackimage ptrs (so don't need to swap the buffers' data)
	std::swap(m_floppyDrive[DRIVE_1].m_disk, m_floppyDrive[DRIVE_2].m_disk);

	// Invalidate the trackimage so that a read latch will re-read the track for the new floppy (GH#543)
	m_floppyDrive[DRIVE_1].m_disk.m_trackimagedata = false;
	m_floppyDrive[DRIVE_2].m_disk.m_trackimagedata = false;

	SaveLastDiskImage(DRIVE_1);
	SaveLastDiskImage(DRIVE_2);

	GetFrame().FrameRefreshStatus(DRAW_LEDS | DRAW_BUTTON_DRIVES);

	return true;
}

//===========================================================================

bool Disk2InterfaceCard::GetFirmware(WORD lpNameId, BYTE* pDst)
{
	BYTE* pData = GetFrame().GetResource(lpNameId, "FIRMWARE", DISK2_FW_SIZE);
	if (!pData)
		return false;

	memcpy(pDst, pData, DISK2_FW_SIZE);
	return true;
}

void Disk2InterfaceCard::InitFirmware(LPBYTE pCxRomPeripheral)
{
	if (pCxRomPeripheral == NULL)
		return;

	ImageInfo* pImage = m_floppyDrive[DRIVE_1].m_disk.m_imagehandle;

	if (m_force13SectorFirmware)
		m_is13SectorFirmware = true;
	else
		m_is13SectorFirmware = ImageIsBootSectorFormatSector13(pImage);

	if (m_is13SectorFirmware)
		memcpy(pCxRomPeripheral + m_slot*APPLE_SLOT_SIZE, m_13SectorFirmware, DISK2_FW_SIZE);
	else
		memcpy(pCxRomPeripheral + m_slot*APPLE_SLOT_SIZE, m_16SectorFirmware, DISK2_FW_SIZE);
}

void Disk2InterfaceCard::InitializeIO(LPBYTE pCxRomPeripheral)
{
	bool res = GetFirmware(IDR_DISK2_13SECTOR_FW, m_13SectorFirmware);
	_ASSERT(res);

	res = GetFirmware(IDR_DISK2_16SECTOR_FW, m_16SectorFirmware);
	_ASSERT(res);

	// Note: We used to disable the track stepping delay in the Disk II controller firmware by
	// patching $C64C with $A9,$00,$EA. Now not doing this since:
	// . Authentic Speed should be authentic
	// . Enhanced Speed runs emulation unthrottled, so removing the delay has negligible effect
	// . Patching the firmware breaks the ADC checksum used by "The CIA Files" (Tricky Dick)
	// . In this case we can patch to compensate for an ADC or EOR checksum but not both (nickw)

	RegisterIoHandler(m_slot, &Disk2InterfaceCard::IORead, &Disk2InterfaceCard::IOWrite, NULL, NULL, this, NULL);

	InitFirmware(pCxRomPeripheral);
}

//===========================================================================

void Disk2InterfaceCard::SetSequencerFunction(WORD addr, ULONG executedCycles)
{
	if ((addr & 0xf) < 0xc)
		return;

	const SEQFUNC oldSeqFunc = m_seqFunc.function;

	switch ((addr & 3) ^ 2)
	{
	case 0: m_seqFunc.writeMode = 0; break;	// $C08E,X (sequence addr A3 input)
	case 1: m_seqFunc.writeMode = 1; break;	// $C08F,X (sequence addr A3 input)
	case 2: m_seqFunc.loadMode = 0; break;	// $C08C,X (sequence addr A2 input)
	case 3: m_seqFunc.loadMode = 1; break;	// $C08D,X (sequence addr A2 input)
	}

	if (!m_seqFunc.writeMode)
		m_writeStarted = false;

	if (oldSeqFunc == checkWriteProtAndInitWrite && m_seqFunc.function != checkWriteProtAndInitWrite)
	{
		// Use up remaining cycles before switching out of "checkWriteProtAndInitWrite" mode
		// Done when checking write-protect, but also for bit-slip (eg. E7) copy-protections
		FloppyDisk& floppy = m_floppyDrive[m_currDrive].m_disk;
		if (ImageIsWOZ(floppy.m_imagehandle))
		{
			const UINT bitCellDelta = GetBitCellDelta(executedCycles);
			UpdateBitStreamPosition(floppy, bitCellDelta);
		}
	}
}

BYTE __stdcall Disk2InterfaceCard::IORead(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULONG nExecutedCycles)
{
	CpuCalcCycles(nExecutedCycles);	// g_nCumulativeCycles needed by most Disk I/O functions

	UINT uSlot = ((addr & 0xff) >> 4) - 8;
	Disk2InterfaceCard* pCard = (Disk2InterfaceCard*) MemGetSlotParameters(uSlot);

	ImageInfo* pImage = pCard->m_floppyDrive[pCard->m_currDrive].m_disk.m_imagehandle;
	bool isWOZ = ImageIsWOZ(pImage);

	if (isWOZ && pCard->m_seqFunc.function == dataShiftWrite)	// Occurs at end of sector write ($C0EE)
		pCard->DataShiftWriteWOZ(pc, addr, nExecutedCycles);	// Finish any previous write

	pCard->SetSequencerFunction(addr, nExecutedCycles);

	switch (addr & 0xF)
	{
	case 0x0:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x1:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x2:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x3:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x4:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x5:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x6:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x7:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x8:	pCard->ControlMotor(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x9:	pCard->ControlMotor(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xA:	isWOZ = pCard->Enable(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xB:	isWOZ = pCard->Enable(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xC:	if (!isWOZ) pCard->ReadWrite(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xD:	pCard->LoadWriteProtect(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xE:	pCard->SetReadMode(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xF:	pCard->SetWriteMode(pc, addr, bWrite, d, nExecutedCycles); break;
	}

	// only even addresses return the latch (UTAIIe Table 9.1)
	if (!(addr & 1))
	{
		if (isWOZ && pCard->m_seqFunc.function != dataShiftWrite)
			pCard->DataLatchReadWriteWOZ(pc, addr, bWrite, nExecutedCycles);

		return pCard->m_floppyLatch;
	}

	return MemReadFloatingBus(nExecutedCycles);
}

BYTE __stdcall Disk2InterfaceCard::IOWrite(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULONG nExecutedCycles)
{
	CpuCalcCycles(nExecutedCycles);	// g_nCumulativeCycles needed by most Disk I/O functions

	UINT uSlot = ((addr & 0xff) >> 4) - 8;
	Disk2InterfaceCard* pCard = (Disk2InterfaceCard*) MemGetSlotParameters(uSlot);

	ImageInfo* pImage = pCard->m_floppyDrive[pCard->m_currDrive].m_disk.m_imagehandle;
	bool isWOZ = ImageIsWOZ(pImage);

	if (isWOZ && pCard->m_seqFunc.function == dataShiftWrite)
		pCard->DataShiftWriteWOZ(pc, addr, nExecutedCycles);	// Finish any previous write

	pCard->SetSequencerFunction(addr, nExecutedCycles);

	switch (addr & 0xF)
	{
	case 0x0:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x1:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x2:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x3:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x4:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x5:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x6:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x7:	pCard->ControlStepper(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x8:	pCard->ControlMotor(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0x9:	pCard->ControlMotor(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xA:	isWOZ = pCard->Enable(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xB:	isWOZ = pCard->Enable(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xC:	if (!isWOZ) pCard->ReadWrite(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xD:	pCard->LoadWriteProtect(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xE:	pCard->SetReadMode(pc, addr, bWrite, d, nExecutedCycles); break;
	case 0xF:	pCard->SetWriteMode(pc, addr, bWrite, d, nExecutedCycles); break;
	}

	// any address writes the latch via sequencer LD command (74LS323 datasheet)
	if (pCard->m_seqFunc.function == dataLoadWrite)
	{
		pCard->m_floppyLatch = d;

		if (isWOZ)
			pCard->DataLatchReadWriteWOZ(pc, addr, bWrite, nExecutedCycles);
	}

	return 0;
}

//===========================================================================

// Unit version history:
// 2: Added: Format Track state & DiskLastCycle
// 3: Added: DiskLastReadLatchCycle
// 4: Added: WOZ state
//    Split up 'Unit' putting some state into a new 'Floppy'
// 5: Added: Sequencer Function
// 6: Added: Drive Connected & Motor On Cycle
// 7: Deprecated SS_YAML_KEY_LSS_RESET_SEQUENCER, SS_YAML_KEY_DISK_ACCESSED
// 8: Added: deferred stepper: event, address & cycle
static const UINT kUNIT_VERSION = 8;

#define SS_YAML_VALUE_CARD_DISK2 "Disk]["

#define SS_YAML_KEY_PHASES "Phases"
#define SS_YAML_KEY_CURRENT_DRIVE "Current Drive"
#define SS_YAML_KEY_DISK_ACCESSED "Disk Accessed"	// deprecated at v7
#define SS_YAML_KEY_ENHANCE_DISK "Enhance Disk"
#define SS_YAML_KEY_FLOPPY_LATCH "Floppy Latch"
#define SS_YAML_KEY_FLOPPY_MOTOR_ON "Floppy Motor On"
#define SS_YAML_KEY_FLOPPY_WRITE_MODE "Floppy Write Mode"	// deprecated at v5
#define SS_YAML_KEY_LAST_CYCLE "Last Cycle"
#define SS_YAML_KEY_LAST_READ_LATCH_CYCLE "Last Read Latch Cycle"
#define SS_YAML_KEY_LSS_SHIFT_REG "LSS Shift Reg"
#define SS_YAML_KEY_LSS_LATCH_DELAY "LSS Latch Delay"
#define SS_YAML_KEY_LSS_RESET_SEQUENCER "LSS Reset Sequencer"	// deprecated at v7
#define SS_YAML_KEY_LSS_SEQUENCER_FUNCTION "LSS Sequencer Function"
#define SS_YAML_KEY_DEFERRED_STEPPER_EVENT "Deferred Stepper Event"
#define SS_YAML_KEY_DEFERRED_STEPPER_ADDRESS "Deferred Stepper Address"
#define SS_YAML_KEY_DEFERRED_STEPPER_CYCLE "Deferred Stepper Cycle"

#define SS_YAML_KEY_DISK2UNIT "Unit"
#define SS_YAML_KEY_DRIVE_CONNECTED "Drive Connected"
#define SS_YAML_KEY_PHASE "Phase"
#define SS_YAML_KEY_PHASE_PRECISE "Phase (precise)"
#define SS_YAML_KEY_TRACK "Track"	// deprecated at v4
#define SS_YAML_KEY_HEAD_WINDOW "Head Window"
#define SS_YAML_KEY_LAST_STEPPER_CYCLE "Last Stepper Cycle"
#define SS_YAML_KEY_MOTOR_ON_CYCLE "Motor On Cycle"

#define SS_YAML_KEY_FLOPPY "Floppy"
#define SS_YAML_KEY_FILENAME "Filename"
#define SS_YAML_KEY_BYTE "Byte"
#define SS_YAML_KEY_NIBBLES "Nibbles"
#define SS_YAML_KEY_BIT_OFFSET "Bit Offset"
#define SS_YAML_KEY_BIT_COUNT "Bit Count"
#define SS_YAML_KEY_EXTRA_CYCLES "Extra Cycles"
#define SS_YAML_KEY_WRITE_PROTECTED "Write Protected"
#define SS_YAML_KEY_SPINNING "Spinning"
#define SS_YAML_KEY_WRITE_LIGHT "Write Light"
#define SS_YAML_KEY_TRACK_IMAGE_DATA "Track Image Data"
#define SS_YAML_KEY_TRACK_IMAGE_DIRTY "Track Image Dirty"
#define SS_YAML_KEY_TRACK_IMAGE "Track Image"

const std::string& Disk2InterfaceCard::GetSnapshotCardName(void)
{
	static const std::string name(SS_YAML_VALUE_CARD_DISK2);
	return name;
}

void Disk2InterfaceCard::SaveSnapshotFloppy(YamlSaveHelper& yamlSaveHelper, UINT unit)
{
	YamlSaveHelper::Label label(yamlSaveHelper, "%s:\n", SS_YAML_KEY_FLOPPY);
	yamlSaveHelper.SaveString(SS_YAML_KEY_FILENAME, m_floppyDrive[unit].m_disk.m_fullname);
	yamlSaveHelper.SaveHexUint16(SS_YAML_KEY_BYTE, m_floppyDrive[unit].m_disk.m_byte);
	yamlSaveHelper.SaveHexUint16(SS_YAML_KEY_NIBBLES, m_floppyDrive[unit].m_disk.m_nibbles);
	yamlSaveHelper.SaveHexUint32(SS_YAML_KEY_BIT_OFFSET, m_floppyDrive[unit].m_disk.m_bitOffset);	// v4
	yamlSaveHelper.SaveHexUint32(SS_YAML_KEY_BIT_COUNT, m_floppyDrive[unit].m_disk.m_bitCount);		// v4
	yamlSaveHelper.SaveDouble(SS_YAML_KEY_EXTRA_CYCLES, m_floppyDrive[unit].m_disk.m_extraCycles);	// v4
	yamlSaveHelper.SaveBool(SS_YAML_KEY_WRITE_PROTECTED, m_floppyDrive[unit].m_disk.m_bWriteProtected);
	yamlSaveHelper.SaveUint(SS_YAML_KEY_TRACK_IMAGE_DATA, m_floppyDrive[unit].m_disk.m_trackimagedata);
	yamlSaveHelper.SaveUint(SS_YAML_KEY_TRACK_IMAGE_DIRTY, m_floppyDrive[unit].m_disk.m_trackimagedirty);

	if (m_floppyDrive[unit].m_disk.m_trackimage)
	{
		YamlSaveHelper::Label image(yamlSaveHelper, "%s:\n", SS_YAML_KEY_TRACK_IMAGE);
		yamlSaveHelper.SaveMemory(m_floppyDrive[unit].m_disk.m_trackimage, ImageGetMaxNibblesPerTrack(m_floppyDrive[unit].m_disk.m_imagehandle));
	}
}

void Disk2InterfaceCard::SaveSnapshotDriveUnit(YamlSaveHelper& yamlSaveHelper, UINT unit)
{
	YamlSaveHelper::Label label(yamlSaveHelper, "%s%d:\n", SS_YAML_KEY_DISK2UNIT, unit);
	yamlSaveHelper.SaveBool(SS_YAML_KEY_DRIVE_CONNECTED, m_floppyDrive[unit].m_isConnected);
	yamlSaveHelper.SaveUint(SS_YAML_KEY_PHASE, m_floppyDrive[unit].m_phase);
	yamlSaveHelper.SaveFloat(SS_YAML_KEY_PHASE_PRECISE, m_floppyDrive[unit].m_phasePrecise);	// v4
	yamlSaveHelper.SaveHexUint4(SS_YAML_KEY_HEAD_WINDOW, m_floppyDrive[unit].m_headWindow);		// v4
	yamlSaveHelper.SaveHexUint64(SS_YAML_KEY_LAST_STEPPER_CYCLE, m_floppyDrive[unit].m_lastStepperCycle);	// v4
	yamlSaveHelper.SaveHexUint64(SS_YAML_KEY_MOTOR_ON_CYCLE, m_floppyDrive[unit].m_motorOnCycle);	// v6
	yamlSaveHelper.SaveUint(SS_YAML_KEY_SPINNING, m_floppyDrive[unit].m_spinning);
	yamlSaveHelper.SaveUint(SS_YAML_KEY_WRITE_LIGHT, m_floppyDrive[unit].m_writelight);

	SaveSnapshotFloppy(yamlSaveHelper, unit);
}

void Disk2InterfaceCard::SaveSnapshot(YamlSaveHelper& yamlSaveHelper)
{
	YamlSaveHelper::Slot slot(yamlSaveHelper, GetSnapshotCardName(), m_slot, kUNIT_VERSION);

	YamlSaveHelper::Label state(yamlSaveHelper, "%s:\n", SS_YAML_KEY_STATE);
	yamlSaveHelper.SaveUint(SS_YAML_KEY_CURRENT_DRIVE, m_currDrive);
	yamlSaveHelper.SaveHexUint4(SS_YAML_KEY_PHASES, m_magnetStates);
	yamlSaveHelper.SaveBool(SS_YAML_KEY_ENHANCE_DISK, m_enhanceDisk);
	yamlSaveHelper.SaveHexUint8(SS_YAML_KEY_FLOPPY_LATCH, m_floppyLatch);
	yamlSaveHelper.SaveBool(SS_YAML_KEY_FLOPPY_MOTOR_ON, m_floppyMotorOn == TRUE);
	yamlSaveHelper.SaveHexUint64(SS_YAML_KEY_LAST_CYCLE, m_diskLastCycle);	// v2
	yamlSaveHelper.SaveHexUint64(SS_YAML_KEY_LAST_READ_LATCH_CYCLE, m_diskLastReadLatchCycle);	// v3
	yamlSaveHelper.SaveHexUint8(SS_YAML_KEY_LSS_SHIFT_REG, m_shiftReg);			// v4
	yamlSaveHelper.SaveInt(SS_YAML_KEY_LSS_LATCH_DELAY, m_latchDelay);			// v4
	yamlSaveHelper.SaveInt(SS_YAML_KEY_LSS_SEQUENCER_FUNCTION, m_seqFunc.function);	// v5
	yamlSaveHelper.SaveBool(SS_YAML_KEY_DEFERRED_STEPPER_EVENT, m_deferredStepperEvent);					// v8
	yamlSaveHelper.SaveHexUint16(SS_YAML_KEY_DEFERRED_STEPPER_ADDRESS, m_deferredStepperAddress);			// v8
	yamlSaveHelper.SaveHexUint64(SS_YAML_KEY_DEFERRED_STEPPER_CYCLE, m_deferredStepperCumulativeCycles);	// v8
	m_formatTrack.SaveSnapshot(yamlSaveHelper);	// v2

	SaveSnapshotDriveUnit(yamlSaveHelper, DRIVE_1);
	SaveSnapshotDriveUnit(yamlSaveHelper, DRIVE_2);
}

bool Disk2InterfaceCard::LoadSnapshotFloppy(YamlLoadHelper& yamlLoadHelper, UINT unit, UINT version, std::vector<BYTE>& track)
{
	std::string filename = yamlLoadHelper.LoadString(SS_YAML_KEY_FILENAME);
	bool bImageError = filename.empty();

	if (!bImageError)
	{
		DWORD dwAttributes = GetFileAttributes(filename.c_str());
		if (dwAttributes == INVALID_FILE_ATTRIBUTES)
		{
			// Get user to browse for file
			UserSelectNewDiskImage(unit, filename.c_str());

			dwAttributes = GetFileAttributes(filename.c_str());
		}

		bImageError = (dwAttributes == INVALID_FILE_ATTRIBUTES);
		if (!bImageError)
		{
			if (InsertDisk(unit, filename, dwAttributes & FILE_ATTRIBUTE_READONLY, IMAGE_DONT_CREATE) != eIMAGE_ERROR_NONE)
				bImageError = true;

			// InsertDisk() zeros m_floppyDrive[unit], then sets up:
			// . m_imagename
			// . m_fullname
			// . m_bWriteProtected
		}
	}

	yamlLoadHelper.LoadBool(SS_YAML_KEY_WRITE_PROTECTED);	// Consume
	m_floppyDrive[unit].m_disk.m_byte = yamlLoadHelper.LoadUint(SS_YAML_KEY_BYTE);
	m_floppyDrive[unit].m_disk.m_nibbles = yamlLoadHelper.LoadUint(SS_YAML_KEY_NIBBLES);
	m_floppyDrive[unit].m_disk.m_trackimagedata = yamlLoadHelper.LoadUint(SS_YAML_KEY_TRACK_IMAGE_DATA) ? true : false;
	m_floppyDrive[unit].m_disk.m_trackimagedirty = yamlLoadHelper.LoadUint(SS_YAML_KEY_TRACK_IMAGE_DIRTY) ? true : false;

	if (version >= 4)
	{
		m_floppyDrive[unit].m_disk.m_bitOffset = yamlLoadHelper.LoadUint(SS_YAML_KEY_BIT_OFFSET);
		m_floppyDrive[unit].m_disk.m_bitCount = yamlLoadHelper.LoadUint(SS_YAML_KEY_BIT_COUNT);
		m_floppyDrive[unit].m_disk.m_extraCycles = yamlLoadHelper.LoadDouble(SS_YAML_KEY_EXTRA_CYCLES);

		if (m_floppyDrive[unit].m_disk.m_bitCount && (m_floppyDrive[unit].m_disk.m_bitOffset >= m_floppyDrive[unit].m_disk.m_bitCount))
			throw std::runtime_error("Disk image: bitOffset >= bitCount");

		if (ImageIsWOZ(m_floppyDrive[unit].m_disk.m_imagehandle))
			UpdateBitStreamOffsets(m_floppyDrive[unit].m_disk);	// overwrites m_byte, inits m_bitMask
	}

	if (yamlLoadHelper.GetSubMap(SS_YAML_KEY_TRACK_IMAGE))
	{
		yamlLoadHelper.LoadMemory(track, ImageGetMaxNibblesPerTrack(m_floppyDrive[unit].m_disk.m_imagehandle));
		yamlLoadHelper.PopMap();
	}

	return bImageError;
}

bool Disk2InterfaceCard::LoadSnapshotDriveUnitv3(YamlLoadHelper& yamlLoadHelper, UINT unit, UINT version, std::vector<BYTE>& track)
{
	_ASSERT(version <= 3);

	std::string disk2UnitName = std::string(SS_YAML_KEY_DISK2UNIT) + (unit == DRIVE_1 ? std::string("0") : std::string("1"));
	if (!yamlLoadHelper.GetSubMap(disk2UnitName))
		throw std::runtime_error("Card: Expected key: " + disk2UnitName);

	bool bImageError = LoadSnapshotFloppy(yamlLoadHelper, unit, version, track);

	yamlLoadHelper.LoadUint(SS_YAML_KEY_TRACK);	// consume
	m_floppyDrive[unit].m_phase = yamlLoadHelper.LoadUint(SS_YAML_KEY_PHASE);
	m_floppyDrive[unit].m_phasePrecise = (float) m_floppyDrive[unit].m_phase;
	m_floppyDrive[unit].m_spinning = yamlLoadHelper.LoadUint(SS_YAML_KEY_SPINNING);
	m_floppyDrive[unit].m_writelight = yamlLoadHelper.LoadUint(SS_YAML_KEY_WRITE_LIGHT);

	yamlLoadHelper.PopMap();

	return bImageError;
}

bool Disk2InterfaceCard::LoadSnapshotDriveUnitv4(YamlLoadHelper& yamlLoadHelper, UINT unit, UINT version, std::vector<BYTE>& track)
{
	_ASSERT(version >= 4);

	std::string disk2UnitName = std::string(SS_YAML_KEY_DISK2UNIT) + (unit == DRIVE_1 ? std::string("0") : std::string("1"));
	if (!yamlLoadHelper.GetSubMap(disk2UnitName))
		throw std::runtime_error("Card: Expected key: " + disk2UnitName);

	if (!yamlLoadHelper.GetSubMap(SS_YAML_KEY_FLOPPY))
		throw std::runtime_error("Card: Expected key: " SS_YAML_KEY_FLOPPY);

	bool bImageError = LoadSnapshotFloppy(yamlLoadHelper, unit, version, track);

	yamlLoadHelper.PopMap();

	//

	m_floppyDrive[unit].m_phase = yamlLoadHelper.LoadUint(SS_YAML_KEY_PHASE);
	m_floppyDrive[unit].m_phasePrecise = yamlLoadHelper.LoadFloat(SS_YAML_KEY_PHASE_PRECISE);
	m_floppyDrive[unit].m_headWindow = yamlLoadHelper.LoadUint(SS_YAML_KEY_HEAD_WINDOW) & 0xf;
	m_floppyDrive[unit].m_lastStepperCycle = yamlLoadHelper.LoadUint64(SS_YAML_KEY_LAST_STEPPER_CYCLE);
	m_floppyDrive[unit].m_spinning = yamlLoadHelper.LoadUint(SS_YAML_KEY_SPINNING);
	m_floppyDrive[unit].m_writelight = yamlLoadHelper.LoadUint(SS_YAML_KEY_WRITE_LIGHT);

	if (version >= 6)
	{
		m_floppyDrive[unit].m_isConnected = yamlLoadHelper.LoadBool(SS_YAML_KEY_DRIVE_CONNECTED);
		m_floppyDrive[unit].m_motorOnCycle = yamlLoadHelper.LoadUint64(SS_YAML_KEY_MOTOR_ON_CYCLE);
	}

	yamlLoadHelper.PopMap();

	return bImageError;
}

void Disk2InterfaceCard::LoadSnapshotDriveUnit(YamlLoadHelper& yamlLoadHelper, UINT unit, UINT version)
{
	bool bImageError = false;
	std::vector<BYTE> track(NIBBLES_PER_TRACK);	// Default size - may expand vector after loading disk image (eg. WOZ Info.largestTrack)

	if (version <= 3)
		bImageError = LoadSnapshotDriveUnitv3(yamlLoadHelper, unit, version, track);
	else
		bImageError = LoadSnapshotDriveUnitv4(yamlLoadHelper, unit, version, track);


	if (!bImageError)
	{
		if ((m_floppyDrive[unit].m_disk.m_trackimage == NULL) && m_floppyDrive[unit].m_disk.m_nibbles)
			AllocTrack(unit, track.size());

		if (m_floppyDrive[unit].m_disk.m_trackimage == NULL)
			bImageError = true;
		else
			memcpy(m_floppyDrive[unit].m_disk.m_trackimage, &track[0], track.size());
	}

	if (bImageError)
	{
		m_floppyDrive[unit].m_disk.m_trackimagedata = false;
		m_floppyDrive[unit].m_disk.m_trackimagedirty = false;
		m_floppyDrive[unit].m_disk.m_nibbles = 0;
	}
}

bool Disk2InterfaceCard::LoadSnapshot(YamlLoadHelper& yamlLoadHelper, UINT version)
{
	if (version < 1 || version > kUNIT_VERSION)
		ThrowErrorInvalidVersion(version);

	m_currDrive = yamlLoadHelper.LoadUint(SS_YAML_KEY_CURRENT_DRIVE);
	m_magnetStates		= yamlLoadHelper.LoadUint(SS_YAML_KEY_PHASES);
	m_enhanceDisk		= yamlLoadHelper.LoadBool(SS_YAML_KEY_ENHANCE_DISK);
	m_floppyLatch		= yamlLoadHelper.LoadUint(SS_YAML_KEY_FLOPPY_LATCH);
	m_floppyMotorOn		= yamlLoadHelper.LoadBool(SS_YAML_KEY_FLOPPY_MOTOR_ON);

	if (version >= 2)
	{
		m_diskLastCycle = yamlLoadHelper.LoadUint64(SS_YAML_KEY_LAST_CYCLE);
		m_formatTrack.LoadSnapshot(yamlLoadHelper);
	}

	if (version >= 3)
	{
		m_diskLastReadLatchCycle = yamlLoadHelper.LoadUint64(SS_YAML_KEY_LAST_READ_LATCH_CYCLE);
	}

	if (version >= 4)
	{
		m_shiftReg			= yamlLoadHelper.LoadUint(SS_YAML_KEY_LSS_SHIFT_REG) & 0xff;
		m_latchDelay		= yamlLoadHelper.LoadInt(SS_YAML_KEY_LSS_LATCH_DELAY);
	}

	if (version >= 4 && version <= 6)
	{
		(void) yamlLoadHelper.LoadBool(SS_YAML_KEY_LSS_RESET_SEQUENCER);	// deprecated
	}

	if (version >= 5)
	{
		m_seqFunc.function = (SEQFUNC) yamlLoadHelper.LoadInt(SS_YAML_KEY_LSS_SEQUENCER_FUNCTION);
	}
	else
	{
		m_seqFunc.writeMode	= yamlLoadHelper.LoadBool(SS_YAML_KEY_FLOPPY_WRITE_MODE) ? 1 : 0;
		m_seqFunc.loadMode = 0;	// Wasn't saved until v5
	}

	if (version <= 6)
	{
		(void) yamlLoadHelper.LoadBool(SS_YAML_KEY_DISK_ACCESSED);	// deprecated - but retrieve the value to avoid the "State: Unknown key (Disk Accessed)" warning
	}

	if (version >= 8)
	{
		m_deferredStepperEvent = yamlLoadHelper.LoadBool(SS_YAML_KEY_DEFERRED_STEPPER_EVENT);
		m_deferredStepperAddress = yamlLoadHelper.LoadUint(SS_YAML_KEY_DEFERRED_STEPPER_ADDRESS);
		m_deferredStepperCumulativeCycles = yamlLoadHelper.LoadUint64(SS_YAML_KEY_DEFERRED_STEPPER_CYCLE);
	}

	// Eject all disks first in case Drive-2 contains disk to be inserted into Drive-1
	for (UINT i=0; i<NUM_DRIVES; i++)
	{
		EjectDisk(i);	// Remove any disk & update Registry to reflect empty drive
		m_floppyDrive[i].clear();
	}

	LoadSnapshotDriveUnit(yamlLoadHelper, DRIVE_1, version);
	LoadSnapshotDriveUnit(yamlLoadHelper, DRIVE_2, version);

	GetFrame().FrameRefreshStatus(DRAW_LEDS | DRAW_BUTTON_DRIVES | DRAW_DISK_STATUS);

	if (m_deferredStepperEvent)
		InsertSyncEvent();

	return true;
}