Exabyte VXA-2, Product Manual, Page: 48 / 90

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P
RODUCT
M
ANUAL
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Chapter 6 O
VERVIEW OF THE
C
OMMAND
P
ROTOCOL
The VXA-2 tape drive is available with a parallel SCSI, IDE/ATAPI, or FireWire
communication interface. All three communication interfaces provide a
method of passing SCSI command descriptor blocks (CDBs) over an bus. The
differences between the interfaces arise primarily from how each interface
handles device addressing and how each handles transmitting SCSI
commands, data, and status between the host and the tape drive. Regardless
of the communication interface, the operation of the tape drive is governed by
the SCSI command protocol.
The following sections describe how the SCSI command protocol is
implemented in the tape drive. Refer to the VXA-2 Tape Drive SCSI Reference
for detailed information about the SCSI command protocol. Refer to the
VXA-2 Tape Drive IDE/ATAPI Reference for detailed information about the
ATAPI protocol. Chapter 7 provides information about the SCSI, IDE/ATAPI,
and FireWire communication interfaces.
SCSI C
OMMAND
P
ROTOCOL
This section provides an overview of the SCSI command protocol supported
by the VXA-2 tape drive.
Note: These commands are transmitted to the IDE/ATAPI tape drive as ATA
Packet commands.
C
OMMAND
S
ET
Table 6-1 lists and briefly describes the command set supported by the tape
drive.
t
Table 6-1 SCSI command set
Command Hex Code Description
ERASE 19h Causes the tape drive to erase all data from the current location to
the end of partition.
INQUIRY 12h Requests that information about drive parameters be sent to the
initiator.
LOAD/UNLOAD 1Bh Causes the tape drive to load or unload a cartridge.
LOCATE 2Bh Positions the tape at a specified logical position or changes partitions.
(Typically, this position is determined by data that was obtained
through a previous READ POSITION command.)
LOG SELECT 4Ch Manages a set of internal counters regarding read and write error
recovery operations and amounts of data compressed. The initiator
can set threshold and cumulative values for the counters or reset the
counters.
LOG SENSE 4Dh Returns the values of the counters managed by the LOG SELECT
command.