Table of Contents
Advertisement
(1)
Operation code
Bit 7
6
Group Code
The top byte of all CDBs shows the format and type of command to be executed.
a. Group Code
The group code specifies the number of bytes and format of the CDB. The groups of
commands shown below are used in the IDD.
•
Group 0 ("000"):
•
Group 1 ("001"):
•
Group 2 ("010"):
•
Group 3 ("110"):
•
Group 4 ("111"):
b. Command Code
Command code specifies the type of command in each group.
(2)
LUN (Logical Unit Number)
This field specifies the address of the logical unit (device) connected under the TARG in cases
where the IDENTIFY message is not used. If the IDENTIFY message is used, the value of the
CDB's LUN field is disregarded when the LUN is specified.
Note:
It is possible that the definition of this field may be changed in future SCSI standards. It is
recommended that the LUN be specified using the IDENTIFY message, and that a zero be
specified in this CDB field.
(3)
Logical Block Address
This field shows the top logical data block address of the data block on the disk media to be
processed by the command. In the group 0 CDB, 21 bit block addressing is possible and in
the group 1, group 2 and group 6 CDBs, 32 bit block addressing is possible. Specifications
for logical data block addressing in the IDD are described in section 1.8.
5
4
3
Command Code
6-byte CDB (Shown in Fig. 1.1)
10-byte CDB (Shown in Fig. 1.2)
10-byte CDB (Shown in Fig. 1.2)
10-byte CDB (Shown in Fig. 1.2)
Reserved Operation Code (Shown in item 1.7.3.)
C141-E039-01EN
2
1
0
1 - 3
Advertisement
Table of Contents
