SCSI bus extension system for controlling individual arbitration on interlinked SCSI bus segments

摘要

This digital communication method and system permits extended distance communication on a SCSI bus despite the time constraints imposed on certain bus operations such as arbitration. The bus system is comprised of discrete bus segments each having a portal node and one or more devices interfaced thereon. All nodes are connected together by a serial link. Each node seizes control of its bus segment and imposes a pseudo-busy condition to prevent bus operations such as arbitration. A token message passed over the serial link between nodes allows one node at a time to release control of its segment to permit arbitration among the devices interfaced on its segment. A source device on the released segment that gains control of the segment as a result of arbitration may communicate with a destination device anywhere on the bus system.