SCSI Inquiry Command

The SCSI Inquiry command is used to obtain basic information from a target device. The CDB structure is:

bit→
↓byte

7

6

5

4

3

2

1

0

0

Operation code = 12h

1

LUN

Reserved

EVPD

2

Page code

3

Reserved

4

Allocation length

5

Control

If the EVPD parameter bit is zero and the Page Code parameter byte is zero then the target will return the standard inquiry data which is structured like this:

bit→
↓byte

7

6

5

4

3

2

1

0

0

Peripheral qualifier

Peripheral device type

1

RMB

Device-type modifier

2

ISO version

ECMA version

ANSI-approved version

3

AEC

TrmIOP

Reserved

Response data format

4

Additional length (n-4)

5

Reserved

6

Reserved

7

RelAdr

WBus32

WBus16

Sync

Linked

Reserved

CmdQue

SftRe

8–15

Vendor identification

16–31

Product identification

32–35

Product revision level

36–55

Vendor-specific

56–95

Reserved

96

Vendor-specific parameters (variable number of bytes)

The special fields in the standard inquiry data have the following meaning:

  • Peripheral Device Type - see separate article on SCSI Peripheral Device Types
  • RMB - removable medium
  • AENC - 1 = supports Asynchronous Event Notifications - (processor devices only)
  • TrmIOP - 1 = supports Terminate I/O Process messages
  • Response data format - 000=SCSI compliant, other values = legacy devices
  • RelAdr - 1= this LUN supports Relative Addressing Mode (linked commands only)
  • WBus32+WBus16 - support for wide data buses:
    • 00 - 8-bit only
    • 01 - 8 or 16-bit
    • 11 - 8, 16 or 32 bit
  • Sync - 1 = supports synchronous transfers
  • Linked - 1 = this LUN supports linked commands
  • CmdQue - 1 = supports Tagged Command Queuing
  • SftRe - 1 = performs soft resets

If the EVPD parameter bit is one then the target will return Vital Product Data (VPD). This can be from one of a number of different pages, depending on the value of the Page Code parameter:

  • 00h - Supported vital product data
  • 01h-7Fh - ASCII information
  • 80h - Unit serial number
  • 81h - Implemented operating definitions
  • 82h - ASCII implemented operating definition
  • 83h-BFh - Reserved
  • C0h-FFh - Vendor-specific

See also

  • SCSI