SCSI Primary Commands - 2.pdf

18 July 2001 T10/1236-D Revision 20A 32-byte variable length CDB format is defined for long LBA operations (see table 7).Table 7 — Typical variable length CDB for long LBA 32-byte commandsBitByte7 6 5 4 3 2 1 00 OPERATION CODE (7Fh)1 CONTROL24Reserved5 Reserved6 Reserved7 ADDITIONAL CDB LENGTH (18h)8 (MSB)SERVICE ACTION9 (LSB)10 Reserved DPO FUA Reserved11 Reserved12 (MSB)LOGICAL BLOCK ADDRESS19 (LSB)2027Additional CDB data28 (MSB)TRANSFER LENGTH (if required)PARAMETER LIST LENGTH (if required)31 ALLOCATION LENGTH (if required)(LSB)4.3.4 Common CDB fields4.3.4.1 Operation codeThe OPERATION CODE field contains the code value identifying the operation being requested by the CDB. SAM-2defines the general structure of the operation code value. The OPERATION CODE field has a consistently definedmeaning across all commands. This standard specifies the operation code values used by the commands definedherein.4.3.4.2 Service actionAll CDB formats except the 6-byte format provide for a SERVICE ACTION field containing a coded value identifying afunction to be performed under the more general command function specified in the OPERATION CODE field. Whilethe SERVICE ACTION field is defined for CDB formats, it is used as described in this subclause only in those CDBformats that contain a SERVICE ACTION field. When the specific field SERVICE ACTION is not defined in a CDB format,the bits identified as the SERVICE ACTION field in a CDB shall be used or reserved as specified by the particular CDBformat.4.3.4.3 Logical block addressThe logical block addresses on a logical unit or within a volume partition shall begin with block zero and becontiguous up to the last logical block of that logical unit or within that partition.dpANS SCSI Primary Commands - 2 (SPC-2) 17