Lucent Technologies USS-720 Instant USB, USB-to-IEEE 1284 Bridge, Preliminary Data Sheet, Rev

Preliminary Data Sheet, Rev. 5								USS-720Instant USB
September 1999							USB-to-IEEE1284 Bridge
IEEE 1284 Port (continued)
Control Register
Table 23. Control Register
				Control Register					Address: 2
Bit		7		6	5	4	3	2	1	0
Symbol		HLH		EPP mask	Direction	Int enbl	SelectIn	nInit	AutoFd	Strobe
Access		R/W		R/W	R/W	R/W	R/W	R/W	R/W	R/W
Default		0		1	0	0	1	1	0	0
Bit	Symbol					Bit Description
7	HLH		Host Logic High. The parallel port HLH signal.
6	EPP mask		EPP Time-Out Interrupt Mask. This bit masks the generation of an interrupt upon
			time-out of an EPP data or address transfer. Note that in typical host-side parallel port
			controller chips, this interrupt condition is grouped with and controlled by the Interrupt
			Enable bit in this register; so for exact emulation of typical parallel port hardware, this
			bit should always be written with the inverse of the Interrupt Enable bit.
5	Direction		Parallel Port Direction. When the Mode field in the Extended Control Register is set
			to 001, this bit controls the direction of the parallel port data lines. When set to 0, the
			lines are in Output Mode, and when set to 1, they are in Input Mode (see the Data
			Register on previous page). This bit also controls the direction of the interface in ECP
			Mode (011). It has no effect in Modes 000 or 010 (which are unidirectional only), or
			100 (where the direction is uniquely determined by the type of access to the EPP
			Registers).
4	Int enbl		Interrupt Enable. This bit enables interrupt generation on nAck events. If this bit is
			set, interrupt status will be generated on transitions of nAck from low to high (this
			status being reflected by the nAck Interrupt bit in the USS-720 Control Register).
3	SelectIn		Inverted nSelectIn. An inverted version of the parallel port nSelectIn signal.
2	nInit		Parallel Port nInit Signal.
1	AutoFd		Inverted nAutoFd. An inverted version of the parallel port nAutoFd signal.
0	Strobe		Inverted nStrobe. An inverted version of the parallel port nStrobe signal.

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