Daniel J Peters

US Patent:

48357375, May 30, 1989

Filed:

Jul 21, 1986

Appl. No.:

6/888498

Inventors:

Hanz W. Herrig - Aurora IL
David N. Horn - Rumson NJ
Daniel V. Peters - Warrenville IL
Randy D. Pfeifer - Warrenville IL
Wayne R. Wilcox - Naperville IL

Assignee:

American Telephone and Telegraph Company, AT&T Bell Laboratories - Murray Hill NJ
AT&T-Information Systems - Holmdel NJ

International Classification:

G06F 1300
G06F 1338
G06F 1340

US Classification:

364900

Abstract:

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.