5.9INQUIRY Command (12h)

The INQUIRY command allows the initiator to determine the kind of SCSI devices attached to its SCSI bus. It causes a device that is attached to a SCSI bus to return information about itself. The drive identifies itself as a Direct Access Storage Device that implements the applicable interfacing protocol. The drive does not need to access its storage medium to respond to the inquiry. The INQUIRY commands are described in Table 5-22and Table 5-23.

The drive can provide two categories of data in response to an INQUIRY command: Standard Inquiry Data and Vital Product Data. Standard Inquiry Data contains basic data about the drive, and Vital Product Data comprises several pages of additional data. Each Vital Product Data page requires a separate INQUIRY command from the initiator.

An INQUIRY command is not affected by, nor does it clear, a Unit Attention condition.

Table 5-22INQUIRY Command Descriptor Block-Data Format

Bit

7

6

5

 

4

 

3

 

2

1

0

Byte

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

Operation

Code (12h)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

Reserved

 

 

 

 

CmdDt

EVPD

 

 

 

 

 

 

 

 

2

 

 

 

Page Code or Operation Code

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

Allocation Length

 

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-23INQUIRY Command Descriptor Block-Field Descriptions

 

 

Field

Description

 

 

CmdDt

Command Support Data. If CmdDt = 0 and EVPD (see below) = 0, the drive returns the

Standard Inquiry Data. If CmdDt = 1 with EVPD = 0, the drive returns the Command Data

 

specified by Page Code/Operation.

EVPD

Enable Vital Product Data. If EVPD = 0 and CmdDt (see above) = 0, the drive returns the

Standard Inquiry Data. If EVPD = 1and CmdDt = 0, the drive returns the Vital Product

 

Data Page specified by Page Code/Operation Code.

 

Specifies the Vital Product Data Page or Command Support Data which is to be returned

Page Code or

by the drive when EVPD is set. Specifies the SCSI Operation Code for command support

data to be returned by the drive when CmdDt is set. A CHECK CONDITION status is re-

Operation Code

turned if this field specifies an unsupported Page or Operation Code or if both EVPD and

 

CmdDt are set. Table 5-27lists the Page Codes for the Vital Product Pages supported by

 

the drive. Table 5-37lists the operation codes for the CmdDt information supported by the

 

drive.

Allocation Length

Specifies the number of bytes of inquiry information the drive is allowed to return to the

initiator during the command's data-in buffer transfer. Error status is not returned if the

 

value in this field truncates the requested information.

Maxtor Atlas 10K V

5-19