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C141-E124-01EN 1 - 3
Bit
Byte
76543210
0 Operation Code
1 LUN 00000
2 Logical Block Address (MSB)
3 Logical Block Address
4 Logical Block Address
5 Logical Block Address (LSB)
6 Transfer Data Length (MSB)
7 Transfer Data Length (LSB)
8 Transfer Data Length (MSB)
9 Transfer Data Length (LSB)
1000000000
11 Control Byte
Figure 1.3 12-Byte CDB Basic Format
The meanings of each of the fields in the CDB are explained below. Depending on the type of
command, the basic format of the CDB, the definitions of fields and their meanings may differ.
Details are described in the specifications for each individual command in Chapter 3.
(1) Operation code
Bit 76543210
Group Code Command Code
The leading 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.
x Group 0 (“000”):6-byte CDB (Shown in Figure 1.1)
x Group 1 (“001”):10-byte CDB (Shown in Figure 1.2)
x Group 2 (“010”):10-byte CDB (Shown in Figure 1.2)
x Group 3 ("011"):Reserved Operation Code (Shown in Section 1.7.3.)
x Group 4 ("100"):16-byte CDB
x Group 5 ("101"):12-byte CDB (Shown in Figure 1.3)