SCSI

SCSI

Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...

 target devices provide a number of SCSI mode pages. These can be interrogated by a Mode Sense command

SCSI Mode Sense Command

The SCSI Mode Sense command is used to obtain current device information from mode pages in a SCSI target device. There are two different versions of the command, a 6 byte version and a 10 byte version.The CDB structure for the Mode Sense command is:...

 and set by a Mode Select command

SCSI Mode Select Command

The SCSI Mode Select command is used to modify device information contained in mode pages in a SCSI target device. There are two different versions of the command, a 6 byte version and a 10 byte version....

. The Mode Sense and Mode Select commands include a 6-bit address field, allowing for 64 possible mode pages. A description of many of these page codes is included below. Note that any given SCSI device type will only support a subset of the possible page codes, and some page codes may have different meanings for different devices.

List of SCSI mode page codes

Code	Description
00h	Vendor-specific
01h	Read-write error recovery parameters
02h	Disconnect-reconnect - allows the initiator to tune SCSI bus performance
03h	Format parameters (direct-access devices)
03h	Measurement units (scanner devices)
04h	Rigid disk geometry parameters
05h	Flexible disk parameters
06h	Optical memory parameters
07h	Verify error recovery parameters
08h	Caching
09h	Peripheral device - transfers vendor-specific data between an initiator and a peripheral interface below the target (obsolete)
0Ah	Control mode - tagged queuing, extended contingent allegiance, asynchronous event notification, and error logging
0Bh	Medium types supported
0Ch	Notch and partition parameters
0Dh	CDROM parameters
0Eh	CDROM audio control (playback) parameters
0Fh	Reserved
10h	Device configuration
11h	Medium partitions (1)
12h	Medium partitions (2)
13h	Medium partitions (3)
14h	Medium partitions (4)
15h	Extended
16h	Extended device-type specific
17h	Reserved
18h	Protocol-specific LUN
19h	Protocol-specific Port
1Ah	Power conditions page
1Bh	Reserved
1Ch	Informational exceptions control
1Dh	medium-changer element address assignment
1Eh	medium-changer transport geometry parameters
1Fh	medium-changer device capabilities
20h-3Eh	Vendor-specific
3Fh	return all mode pages (valid only for a Mode Sense command)