In-system Design, Inc.

Ronald J Richter

David C Gilbert

Scott Alan DeHart

David D Luke

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

The current augmentation method is for use with a computer powered peripheral subsystem including a dynamic load, the dynamic load requiring greater power, from time to time, than the specified power available from the computer and specified interconnect bus or interface. This method includes use of a power node supplying power as necessary from the battery to the dynamic load, such that the varying dynamic load does not exceed the specified power available from the computer and interconnect bus. The method includes monitoring the load current, and injecting current into the power node to augment the current drive capability of the computer and peripheral bus. Preferably, the injecting is performed selectively based upon the result of the monitoring, e.g. only when the sensed load current is approaching a defined threshold level. Further, battery charging is performed only when it is determined that no current is being drawn through the battery to avoid distorting the voltage reading. The invented apparatus is also for selectively charging the battery from the current on the bus during relatively idle periods of peripheral dynamic load. The apparatus includes means for determining the chargeability of the battery in accordance with predefined chargeability criteria, and a battery charging circuit responsive to the determining means for selectively charging the battery only during times when the peripheral load current is limited and there is sufficient current available on the bus from the computer to recharge the battery.

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Boise, ID, United States of America

Ronald J Richter