User Manual

SCSI Commands Reference Manual, Rev. J 38
www.seagate.com General Concepts
2.1.2 The fixed length CDB formats
All fixed length CDBs shall have an OPERATION CODE field as their first byte and a CONTROL byte as their last byte. Table 2 shows
the typical format of a 6-byte CDB. Table 3 shows the typical format of a 10-byte CDB. Table 4 shows the typical format of a
12-byte CDB. Table 5 shows the format of a 16-byte CDB for commands that provide for a long LBA.
Table 2 Typical CDB for 6-byte commands
Bit
Byte
7 6 5 4 3 2 1 0
0
OPERATION CODE
1
Miscellaneous CDB information (MSB)
2
LOGICAL BLOCK ADDRESS (if required)
3
(LSB)
4
TRANSFER LENGTH (if required)
PARAMETER LIST LENGTH (if required)
ALLOCATION LENGTH (if required)
5
CONTROL
Table 3 Typical CDB for 10-byte commands
Bit
Byte
7 6 5 4 3 2 1 0
0
OPERATION CODE
1
Miscellaneous CDB information SERVICE ACTION (if required)
2
(MSB)
LOGICAL BLOCK ADDRESS (if required)
. . .
5
(LSB)
6
Miscellaneous CDB information
7
(MSB) TRANSFER LENGTH (if required)
PARAMETER LIST LENGTH (if required)
ALLOCATION LENGTH (if required)
8
(LSB)
9
CONTROL