Karl Suss America, Inc.

James B Pitman

R Emmett Hughlett

Walter Bohler

Michael E Forsberg

Apparatus and method for collision avoidance in a multinode data communications bus, the bus having a plurality of nodes coupled thereto for transmitting and receiving data over the bus, the bus further including a BUS BUSY signal line bidirectionally connected in common between the nodes, each of the nodes being operable for asserting the BUS BUSY signal line and also for determining the state of the BUS BUSY signal line. In accordance with the invention there is disclosed, for a node having data to transmit on the bus: (a) testing the state of the BUS BUSY line to determine if the line is asserted; (b) asserting, if the line is determined not to be asserted, the BUS BUSY line for a first predetermined interval of time; (c) deasserting the BUS BUSY line for a second predetermined interval of time; (d) testing the state of the BUS BUSY line to determine if the line is asserted; (e) asserting, if the BUS BUSY line is determined to be not asserted, the BUS BUSY line; (f) transmitting the data; and (g) deasserting the BUS BUSY line.

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Waterbury Ctr., VT, United States of America

James B Pitman