Seagate Ultra 160 - Manual (Page 146)

132 Parallel SCSI Interface Product Manual, Rev. A
The Command Descriptor Block always has an operation code as the first byte of the command. This is fol-
lowed by command parameters (if any), and a control field.
For all commands, if there is an invalid parameter in the Command Descriptor Block, the drive shall terminate
the command without altering the medium.
The format description for the Command Descriptor Block as supported by Seagate drives is shown in tables
57, 58, 59, 60, and 61.