SCSI Commands
Page
17
Conventions
The commands in this chapter are listed in alphabetical order. Each command is
described, its Command Descriptor Block (CDB) illustrated, and the Completion
Status is given. Bits and fields defined in the ANSI SCSI documents that are not
used by the drive are not described in this document. Bits and fields that are
supported by the drive are described.
Command Descriptor Blocks
A host makes request of the tape drive by sending a Command Descriptor Block
(CDB). Some commands also require a parameter list. If the CDB or the parameter
list contains an invalid parameter, the drive terminates the command, returning a
Sense Key of Illegal Request, without altering the medium.
Command Descriptor Block Formats
SCSI six-byte Command Descriptor Blocks are arranged in the format shown in the
following table.
Byte
Bits
7
6
5
4
3
2
1
0
0
Operation Code
1
Ignored LUN
Command Dependent
2
Command Dependent
3
Command Dependent
4
Command Dependent
5
Control
SCSI ten-byte Command Descriptor Blocks are arranged in the format shown in the
following table.
Byte
Bits
7
6
5
4
3
2
1
0
0
Operation Code
1
Ignored LUN
Command Dependent
2
Command Dependent
3
Command Dependent
4
Command Dependent
5
Command Dependent
6
Command Dependent
7
Command Dependent
8
Command Dependent
9
Control
Field names that are centered represent fields that are at least one byte long. Field
names that are left-aligned with a bit number are one or more bits long. The length is
indicated by the beginning of the following field name, and by the Bits column in the
Field Descriptions table, shown below.
