Inquiry Command (12H) - Seagate SCSI Interface Product Manual

SCSI Interface Product Manual, Rev. J
5.6

Inquiry command (12h)

The Inquiry command requests that information regarding parameters of the drive be sent to the initiator. An
option Enable Vital Product Data (EVPD) allows the initiator to request additional information about the drive.
See paragraph 5.6.2. Several Inquiry commands may be sent to request the vital product data pages instead of
the standard data shown in Table 49.
Table 48: Inquiry command (12h)
Bit 7
Byte
0 0
1 0
Logical Unit Number [1]
2 Page Code [3]
3 0
4 Allocation Length in Bytes [4]
5 0
Notes.
[1] The Logical Unit Number must be zero.
[2] An Enable Vital Product Data (EVPD) bit of one specifies that the drive shall return the vital product data
specified by the page code field. An EVPD bit of zero specifies that the drive shall return the standard
Inquiry data.
[3] The Page Code field specifies the page of vital product data information that the drive shall return. If the
EVPD bit is zero and the page code field is not zero the drive shall return Check Condition status with the
sense key set to Illegal Request and an additional sense code of Invalid Field in CDB.
[4] The Allocation Length specifies the number of bytes that the initiator has allocated for returned data. The
drive shall terminate the Data In phase when Allocation Length bytes have been transferred or when all
available data have been transferred to the initiator, whichever is less.
[5] See "Control byte," paragraph 4.2.6.
The Inquiry command returns Check Condition status only when the drive cannot return the requested Inquiry
data.
If an Inquiry command is received from an initiator with a pending unit attention condition (i.e., before the drive
reports Check Condition status), the drive performs the Inquiry command and does not clear the unit attention
condition.
The Inquiry command is typically used by the initiator after a reset or power-up condition to determine the
device types for system configuration. To minimize delays after a reset or power-up condition, the standard
Inquiry data is available without incurring any media access delays. Since the drive stores some of the Inquiry
data on the device media, it may return zeros or ASCII spaces (20h) in those fields until the data is available.
The Inquiry data may change as the drive executes its initialization sequence or in response to a Change Defi-
nition command. For example, the drive may contain a minimum command set in its non-volatile memory and
load its final firmware from the medium when it becomes ready. After it has loaded the firmware, it may support
more options and therefore return different supported options information in the Inquiry data.
6 5
0 0
0 0
0 0
0 0
4 3
1 0
0 0
0 0
0 0
2 1
0 1
0 0 EVPD [2]
0 0
0 Flag [5] Link [5]
87
0
0
0