User Manual

SCSI Commands Reference Manual, Rev. J 44
www.seagate.com General Concepts
2.2.7 CONTROL
The CONTROL byte has the same definition for all commands.
All CDBs shall contain a CONTROL byte (see table 10). The location of the CONTROL byte within a CDB depends on the CDB
format (see 2.1.2 and 2.1.3).
Table 10 CONTROL byte
All SCSI transport protocol standards shall define the functionality needed for a logical unit to implement the NACA bit.
NACA (Normal ACA) bit
The NACA (Normal ACA) bit specifies whether an auto contingent allegiance (ACA) is established if the command returns with CHECK CONDI-
TION status. An NACA bit set to one specifies that an ACA shall be established.
0 An NACA bit set to zero specifies that an ACA shall not be established. The actions for ACA are specified in SAM-5. Actions that may be
required when an ACA is not established are described in SAM-5. All logical units shall implement support for the NACA value of zero
and may support the NACA value of one (i.e., ACA). The ability to support a NACA value of one is indicated with the NORMACA bit in the
standard INQUIRY data (see clause 3.6.2)
1 If the NACA bit is set to one but the logical unit does not support ACA, the command shall be terminated with CHECK CONDITION status,
with the sense key set to ILLEGAL REQUEST, and the additional sense code set to INVALID FIELD IN CDB.
2.2.8 GROUPING FUNCTION
A grouping function is a function that collects information about attributes associated with commands (i.e., information about
commands with the same group value are collected into the specified group). The definition of the attributes and the groups is
outside the scope of this manual. Groups are identified with the GROUP NUMBER field in the CDB of certain commands (e.g., the
WRITE (10) command (see 3.60)).
The collection of this information is outside the scope of this manual (e.g., the information may not be transmitted using any
SCSI protocols).
Support for the grouping function is indicated in the GROUP_SUP bit in the Extended INQUIRY Data VPD page (see 5.4.9).
Bit 7 6 5 4 3 2 1 0
Vendor Specific Reserved NACA Obsolete Obsolete