In-system Design, Inc.

David D Luke

David C Gilbert

James E Castleberry

Lynn R Watson

Ronald J Richter

Eric J Luttmann

A Universal Serial Bus (USB) peripheral bridge and method for operation are disclosed. The bridge simulates a device disconnect condition to its upstream USB hub or host, even though it remains connected and powered, when its associated peripheral is not ready to communicate, powered off, or physically disconnected. For an IEEE-1284-1994 peripheral connection, the bridge senses the condition of the PLH peripheral line. If the PLH line is deasserted or floating, the bridge simulates a device disconnect condition by either allowing its upstream hub or host to take the D&plus; data line low, or taking the line low itself. By not allowing itself to be enumerated on the USB unless its associated peripheral is ready, the bridge avoids confusion at the host and wasted bus resources. At the same time, the bridge may remain physically connected to the host regardless of the state of the peripheral, even if the bridge is powered from the host.

Universal serial bus peripheral bridge simulates a device disconnect condition to a host when the device is in a not-ready condition to avoid wasting bus resources

A Universal Serial Bus to parallel bus bridge includes a Universal Serial Bus port that receives a serial bit stream of data and commands in a Universal Serial Bus protocol from a USB host computer. A parallel bus port on the bridge includes parallel port registers and state machines coupled to a peripheral device. A USB controller core is coupled between the Universal Serial Bus port and the parallel bus port and converts data and commands between the Universal Serial Bus protocol and the parallel bus protocol. A sequencer is coupled between the USB controller core and the parallel bus port. A sequence of sequencer commands is loaded into memory in the USB bridge and used by the sequencer to perform a sequence of parallel port operations. The sequencer performs the commands autonomously without intervention from the USB host computer. Because the host computer does not have to initiate a USB transaction for each individual parallel port operation, the sequence of operations is completed in a shorter amount of time.

Universal serial bus peripheral bridge with sequencer

A serial to parallel port signal converter for interconnection between a hosts utilizing Uniform Serial Bus communications protocols and a peripheral device uses IEEE 1284 complaint communications protocol. The signal converter appears to the host as a fully compliant bi-directional USB device, and to the peripheral device as a fully compliant IEEE 1284 host.

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Boise, ID, United States of America

David D Luke