Quantum 10K II - Manual (Page 72)

SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–5
5.2 Command Descriptor Block
An initiator communicates with the drive by sending a 6-, 10-, or 12-byte Command
Descriptor Block (CDB) that contains the parameters for the specific command. The
SCSI command's operation code is always the first byte in the CDB and a control
field is the last byte. For some commands, the CDB is accompanied by a list of
parameters sent during the data-out buffer transfer. Figure 5-1 shows the format of a
typical 6-byte CDB.
Table 5-2 contains a description of the CDB fields.