Appeal No. 2001-2236
Application 07/955,669
BACKGROUND
The disclosed invention relates to a method and device for
selecting a device on a SCSI bus without that device having an
assigned SCSI address. One problem with the SCSI standard is
that it only provides for eight SCSI addresses, which are
identified by one of eight lines on the SCSI data bus DB<7..0>.
Normally, two devices, an initiator and a target, communicate by
setting two corresponding bits on the SCSI data bus DB<7..0>.
In the invention, if a target without an assigned SCSI address
determines that only one bit is set on the SCSI data bus, it
knows that it has been selected and responds on the SCSI bus.
The invention in effect provides for an extra SCSI address
without being inconsistent with the SCSI standard.
Claim 1 is reproduced below.
1. A method of communicating on a SCSI bus between an
initiator device and a separate target device, the separate
target device not being assigned a SCSI address, comprising
the steps of:
providing the initiator device and the separate target
device on the SCSI bus as physically separate devices;
the separate target device monitoring the signals on
the SCSI bus for the start of a SELECTION phase;
the separate target device determining during the
SELECTION phase whether any single bit of the SCSI data bus
is asserted to indicate the initiator device selecting
itself as a target; and
if any single bit of the SCSI data bus is asserted, the
separate target device responding on the SCSI bus.
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