User Manual

SCSI Commands Reference Manual, Rev. J 186
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
CDB SIZE field
The CDB SIZE field contains the size of the CDB USAGE DATA field in the parameter data, and the number of bytes in the CDB for command
being queried (i.e., the command specified by the REPORTING OPTIONS, REQUESTED OPERATION CODE, and REQUESTED SERVICE ACTION
fields in the REPORT SUPPORTED OPERATION CODES CDB).
CDB USAGE DATA field
The CDB USAGE DATA field contains information about the CDB for the command being queried. The first byte of the CDB USAGE DATA field
shall contain the operation code for the command being queried. If the command being queried contains a service action, then that service
action code shall be placed in the CDB USAGE DATA field in the same location as the SERVICE ACTION field of the command CDB. All other
bytes of the CDB USAGE DATA field shall contain a usage map for bits in the CDB for the command being queried.
The bits in the usage map shall have a one-for-one correspondence to the CDB for the command being queried. If the device server evaluated
a bit in the CDB for the command being queried, the usage map shall contain a one in the corresponding bit position. If any bit representing
part of a field is returned as one, all bits for the field shall be returned as one. If the device server ignores or treats as reserved a bit in the CDB for
the command being queried, the usage map shall contain a zero in the corresponding bit position. The usage map bits for a given CDB field all
shall have the same value.
For example, the CDB usage bit map for the REPORT SUPPORTED OPERATION CODES command is: A3h, 0Ch, 87h, FFh, FFh, FFh, FFh, FFh, FFh,
FFh, 00h, 07h. This example assumes that the logical unit only supports the low-order three bits of the CDB CONTROL byte. The first byte con
-
tains the operation code, and the second byte contains three reserved bits and the service action. The remaining bytes contain the usage map.
RCTD (Report Command Timeout Descriptor) bit
0 If the RCTD bit is set to zero, the command timeouts descriptor shall not be included.
1 If the RCTD bit is set to one in the REPORT SUPPORTED OPERATION CODES CDB, the command timeouts descriptor shall be included.