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	CardInterface -- Determine the type of card interface.

	return = CardInterface()

	ULONG CardInterface( void );

	This function is used to determine the type of credit-card
	(hardware) interface available.  For the most part the
	card.resource hides the hardware details from devices within its
	function calls.  However should we need to provide a work-around
	because of differences, or limitations imposed by future interface
	hardware, this function must be used to identify which interface
	is available.

	A ULONG value as defined in card.h/i.

	In general only I/O devices (e.g., a device which interfaces
	with a modem card) would need to provide work-arounds,
	or alternative code.  An example would be a change in the way
	interrupt requests from the card are handled.  Specific details
	will be provided as need in the future.  I/O devices) should abort
	properly if this function returns a value which is unknown.

	Current implementations (see card.h/i) -


	The card slot can be configured for use as an I/O interface
	by using the CardMiscControl() function.

	The card slot inhibits writes to cards which do not negate
	the WP status bit.  This can be overridden by using the
	CardMiscControl() function.

	Changes in the interrupt request line are latched by a gate-array,
	and have to be obtained via the status change mechanism provided
	when you call the OwnCard() function.  The interrupt is cleared
	when you return from the status change interrupt.  A level 2
	interrupt is generated.  Usually you will want to clear the
	interrupt on the card at this time, and Signal() a task.  The IRQ
	line is the same as the RDY/BSY line.

	Changes in BVD1, WP, and RDY/BSY are also latched by the gate-array,
	and are obtainable via the status change mechanism provided by
	the OwnCard() function.  A level 2 interrupt is generated.

	Changes in BVD2 (also used for digital audio) have to be
	monitored via polling.  Generally this will cause no problem.
	Monitoring changes in BVD1 & BVD2 to monitor for low battery
	condition can be handled by a low priority tool which periodically
	checks the condition of both lines using the ReadCardStatus()

	As of card.resource V39 (check VERSION in resource base), the
	CardMiscControl() function can be used to enable/disable
	status change interrupts for changes in BVD1, BVD2, and the
	RDY/BSY status line.  Status change interrupts for WR
	(Write-protect enable/disable) are always enabled.  The default
	state of enabled/disabled status change interrupts noted above
	are unchanged, and automatically reset to the defaults when
	a card is removed, or when even a task releases ownership
	of the card.

	Some PC oriented eight (8) bit cards may require you read
	odd-byte I/O address registers at the corresponding even-byte
	address plus 64K.  There is sufficient I/O address space
	provided that exceeding I/O address space should not be a problem.

	Your code should wait at least 1 millisecond for Vpp to stabilize
	after voltage change (see CardProgramVoltage()).

	CardMiscControl(), resources/card.i, resources/card.h

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