SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–33
5.11 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 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.
Bit
Byte
7 6 5 4 3 2 1 0
0Operation Code (12h)
1Reserved CmdDt EVPD
2Page Code or Operation Code
3Reserved
4Allocation Length
5Control
Figure 5–10 INQUIRY Command Descriptor Block — Data Format
Table 5–12 INQUIRY 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.
(continued)