Data processing system having a star coupler with contention circuitry

摘要

A data processing system having a plurality of subsystems linked by a star coupler. The star coupler includes contention circuitry for controlling the star coupler so that at any given time no more than one selected subsystem can pass a message through the star coupler. The contention circuitry uses a conventional priority encode circuit to determine the selected one of the subsystems, so that the first message to be received from one of the subsystems is the message passed or, if two or more messages are received from subsystems simultaneously, the message from the subsystem having the highest relative priority established by the priority encode circuit is the message passed. In an embodiment showing an expanded star coupler, the contention circuitry has plural first level contention circuits and a second level contention circuit, each using a conventional priority encode circuit.