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Data processing system having a star coupler with contention circuitry

  • US 4,428,046 A
  • Filed: 05/05/1980
  • Issued: 01/24/1984
  • Est. Priority Date: 05/05/1980
  • Status: Expired due to Term
First Claim
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1. A data processing system, comprising:

  • a plurality of subsystems, wherein each subsystem has an active condition when generating a message and an idle condition when no message is being generated, and wherein each subsystem generates a stream of repetitive binary bits when in its idle condition;

    first transmission means associated with each subsystem for carrying messages from the associated subsystem when the associated subsystem is in its active condition, and for carrying said stream of repetitive binary signals from the associated subsystem when the associated subsystem is in its idle condition;

    second transmission means associated with each subsystem for carrying messages to the associated subsystem, and for carrying said repetitive binary signals to the associated subsystem;

    a star coupler for linking each first transmission means to every second transmission means so that a message from the first transmission means associated with one of said subsystems can be passed to the second transmission means associated with every subsystem, including contention circuitry in the star coupler for selecting one subsystem and controlling the star coupler so that only the messages from the first transmission means of the selected subsystem are passed through the star coupler to each second transmission means associated with every subsystem, and wherein said contention circuitry comprises means for controlling the star coupler to pass only the meassage received first in time at the star coupler, and for assigning a relative priority to each of said subsystems, for controlling the star coupler so that, if the beginning of more than one message is received simultaneously from more than one subsystem, only the message from the first transmission means associated with the subsystem having a higher assigned priority is passed to each second transmission means wherein said contention circuitry includes means for detecting the absence of a message on any first transmission means;

    first gate means associated with each subsystem, each first gate means being connected to the first transmission means of its associated subsystem for receiving any message generated from its associated subsystem, and each first gate means being controlled by the contention circuitry to pass a message only when its associated subsystem has been selected by the contention circuitry;

    second gate means associated with each subsystem, each second gate means being connected to every first gate means for receiving messages passed by each first gate means, each second gate means being connected to the second transmission means of its associated subsystem to pass a message thereto, each second gate means being controlled by the contention circuitry so that when one of the subsystems has been selected to have its message passed through the star coupler, each second gate means receives the message from the first gate means associated with the selected subsystem and passes the message to the second transmission means of its associated subsystem; and

    third gate means associated with each subsystem, each third gate means connected between the first transmission means and the second transmission means of its associated subsystem and controlled by the means for detecting the absence of a message so that when all of the subsystems are in an idle condition, the repetitive binary signals from each subsystem are passed through the third gate means back to the same subsystem.

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