In
SCSI
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interface ...
standards for transferring data between computers and
peripheral devices, often
computer storage
Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The central processing unit (CPU) of a compute ...
,
commands
Command may refer to:
Computing
* Command (computing), a statement in a computer language
* COMMAND.COM, the default operating system shell and command-line interpreter for DOS
* Command key, a modifier key on Apple Macintosh computer keyboards
* ...
are sent in a Command Descriptor Block (CDB).
Each CDB can be a total of 6, 10, 12, or 16 bytes, but later versions of the SCSI standard also allow for variable-length CDBs. The CDB consists of a one byte operation code followed by some command-specific parameters. The parameters need not be a full byte long, and the parameter length varies from one command to another. The available commands, with links to articles describing the detailed structure of many of them, are listed in the article section
List of SCSI commands.
Typical CDB structures, for the 6- and 16-byte
SCSI Request Sense Command
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interface ...
, opcode 3, are:
6-byte CDB:
16-byte CDB:
An example with different allocation of bits to parameters is the 6-byte
SCSI Mode Sense Command
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interfaces ...
:
[ SCSI Command Reference, pp.97-100.]
The generic form of the 12-byte CDB is:
See SPC-4 (http://www.t10.org/cgi-bin/ac.pl?t=f&f=spc4r34.pdf, free registration required) for more information.
Notes
See also
*
LUN LUN or Lun may refer to:
* Logical unit number
In computer storage, a logical unit number, or LUN, is a number used to identify a logical unit, which is a device addressed by the SCSI protocol or by Storage Area Network protocols that encapsulate ...
References
*
CDB
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