Exabyte VXA-2, Product Manual, Page: 54 / 90

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P
RODUCT
M
ANUAL
1009541
Chapter 7 O
VERVIEW OF THE
C
OMMUNICATION
I
NTERFACE
SCSI M
ESSAGE SYSTEM
The SCSI message system allows communication between a SCSI initiator and
the VXA-2 tape drive for interface management. A message can be one byte or
multiple bytes. Table 7-1 describes the SCSI messages that the tape drive
supports.
Table 7-1 Supported SCSI messages
Message Hex Code Description
Command Complete 00h The tape drive sends the Command Complete message to the
initiator to indicate that the execution of the command has
completed and that valid status has been sent to the initiator.
After the tape drive successfully sends this message, the bus goes
to the Bus Free phase.
Extended Messages 01h Synchronous Data Transfer Request (01h) The initiator starts
negotiations for synchronous data transfer.
Wide Data Transfer Request (03h) The initiator starts
negotiations for wide data transfer.
Save Data Pointers 02h The tape drive sends the Save Data Pointers message to direct the
initiator to save a copy of its present active data pointers for the
tape drive.
Restore Data Pointers 03h The tape drive sends the Restore Pointers message to inform the
initiator that it did not properly receive a block of data or the
command descriptor block (CDB) and that the data needs to be
transferred again.
Disconnect 04h The tape drive sends the Disconnect message to inform the
initiator that it is about to break the present physical path and that
a later reconnection is required to complete the current
operation.
Initiator Detected
Error
05h The initiator sends the Initiator Detected Error message to inform
the tape drive that an error has occurred that does not preclude
the tape drive from retrying the operation.
Abort 06h The initiator sends the Abort message to the tape drive to clear
the present operation. All pending data and status for the issuing
initiator are cleared.
Message Reject 07h Either the initiator or the tape drive can send the Message Reject
message to indicate that the last message it received was
inappropriate or not supported.
No Operation 08h The initiator sends the No Operation message in response to the
tape drive’s request for a message when the initiator does not
currently have a valid message to send.
Message Parity Error 09h The initiator sends the Message Parity Error message to the tape
drive to indicate that the last message byte it received had a parity
error.