At+t Corp.

American Telephone & Telegraph Co., At&t Bell Laboratories

At&t Information Systems Inc.

Wayne R Wilcox

Mikiel L Larson

Hanz Werner Herrig

Randy D Pfeifer

David N Horn

Daniel V Peters

An arbitration circuit that uses a unique history register that is combined with a value representing bus requests to index into a table. All possible combinations of history register requests are stored in the table along with a corresponding grant. A block of the table is selected by the history register, and then the request is used to index into the block to determine which request receives a grant. The grant is then shifted into the history register. Advantageously, more than one table may be stored in memory which can be selected by an arbiter controller.

Dynamically programmable bus arbiter with provisions for historical

An electronic circuit board electrically connected to other circuits of a data processing system by means of a bus, may be removed and re-inserted in the system without the necessity of disabling other circuits connected to the bus. A latch actuated switch provides a control signal in anticipation of circuit board removal. The control signal activates a finite state machine which seizes control of the bus after completion of any current bus communications and stops the generation of clock pulses normally required in bus communications. When contact is physically broken between the board and its corresponding connector, the finite state machine restores the bus clock pulses and relinquishes control of the bus. When a board is to be inserted in an open connector, contact between the board and the connector is sensed by the finite state machine which causes the bus to be seized and the bus clock pulses to be temporarily inhibited. When the board is fully inserted, the finite state machine restores the bus clock pulses and relinquishes control of the bus.

Method and apparatus for controlled removal and insertion of circuit

Growing community of inventors

Naperville, IL, United States of America

Wayne R Wilcox