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Maxtor Atlas 10K V 5-19
5.9 INQUIRY 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 5-22 and 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 5-22 INQUIRY Command Descriptor Block-Data Format
Table 5-23 INQUIRY Command Descriptor Block-Field Descriptions
Bit
Byte
765 4 3210
0 Operation Code (12h)
1ReservedCmdDtEVPD
2 Page Code or Operation Code
3 Reserved
4 Allocation Length
5 Control
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.
Page Code or
Operation Code
Specifies the Vital Product Data Page or Command Support Data which is to be returned
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-
turned if this field specifies an unsupported Page or Operation Code or if both EVPD and
CmdDt are set. Table 5-27 lists the Page Codes for the Vital Product Pages supported by
the drive. Table 5-37 lists 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.