ARRANGEMENT FOR EXPANDING THE DEVICE CAPACITY OF A BUS

摘要

An arrangement that allows banks of up to eight duplicated active devices to be connected to a SCSI bus and to share SCSI device IDs, and also allows multiple hosts to share the SCSI bus and the connected active devices. Tri-state buffers act as gates to interface host adapters of a plurality of hosts, and act ive devices of a plurality of device banks, to the SCSI bus. The gate of only one ho st adapter and the gates of only one bank of devices are enabled at any one time. Only the devices of the enabled bank can receive and respond to addresses from t he SCSI bus, while the devices of the other banks are prevented from receiving and responding to addresses from the SCSI bus. Each host has a tri-state buffer acti ng as bank selector for selecting one of the device banks, by enabling the gates of the devices of the selected bank through a bank select bus. Only one host's bank selector is enabled at any one time.