Quantum LTO 3 User Manual page 32

SCSI Commands: 14BSCSI Command Descriptor Blocks
3.2.1.1
Bits
Byte 7
8
9
SCSI 12-byte Command Descriptor Blocks are arranged in the format shown in the
following table.
Bits
Byte 7
0
1 Ignored LUN
2
3
4
5
6
7
8
9
10
11
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 on the following page.
SCSI Command Descriptor Block Field Descriptions
Field Byte Bits
Operation 0
Code
Ignored
1 5-7
Logical
Unit
Service 1 0-4
Action
Command 12-4 0-4
Dependent 2-8
2-8
Reserved
Control Last
Fields that are one byte or longer have no entry in the Bits column.
6 5 4
Command Dependent
Control
6 5 4
Operation Code
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Command Dependent
Control
Description
The Operation Code is made up of the Group Code and the
Command Code. See Operation Code Format, below.
The LUN field is vestigial from the SCSI-1 standard and is ignored.
Value identifying a function to be performed under the more general
command function specified in the OPERATION CODE field.
See the specific command.
All reserved bits must be 0.
The Control byte is made up of the Vendor Unique, Flag and Link
bits. See Control Format, below.
3 2 1
3 2 1
Service Action
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