
2.1 Overview of SCSI Communication
Table 2-1 shows the commands, status information, and messages that
are supported by the CTS during SCSI bus phases.
SCSI Bus Phase Explanation
Bus Free
BSY and SEL are false. The SCSI bus is idle and available for
arbitration.
Arbitration
BSY and SCSI ID assertion (highest ID wins).
Selection
Winning ID asserts SEL. The initiator releases I/O and BSY.
The CTS sets BSY. The initiator releases SEL and asserts ATN.
Message Out
The initiator sends the Identify message and indicates whether
disconnects are permitted. Other messages supported during the
Message Out phase, but in a different bus sequence include:
Extended Message (Synchronous Data Transfer Request)
Initiator Detected Error
Abort
Message Reject
No Operation
Message Parity Error
Bus Device Reset
Command
The CTS switches to Command Phase. The Initiator sends the
command CDB. Commands supported by the CTS include:
ERASE
INQUIRY
LOAD/UNLOAD
LOCATE
LOG SELECT
LOG SENSE
MODE SELECT
MODE SENSE
PREVENT/ALLOW MEDIUM
REMOVAL
READ
READ BLOCK LIMITS
READ BUFFER
READ POSITION
RECEIVE DIAGNOSTIC
RESULTS
RELEASE UNIT
REQUEST SENSE
RESERVE UNIT
REWIND
SEND DIAGNOSTIC
SPACE
TEST UNIT READY
VERIFY
WRITE
WRITE BUFFER
WRITE FILEMARKS
Table 2-1 Overview of SCSI communication
2-2
EXB-8205 and EXB-8505
(Standard and XL)
510503
2 SCSI Communication
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