Information Technology Reference
In-Depth Information
command, except that a verification of the data written to the destination logical unit is
performed after the data is written.
•
Inquiry
(12h). This command requests that information regarding parameters of the target
and its attached peripheral device(s) be sent to the initiator.
•
Log select (4Ch). This command provides a means for the initiator to manage statistical
information maintained by the device about the device or its logical units. Targets that
implement the log select command shall also implement the log sense command. Struc-
tures in the form of log parameters within log pages are defined as a way to manage the
log data. The log select command provides for sending zero or more log pages during a
data out phase.
•
Log sense (4Dh). This command allows the initiator to retrieve statistical information
maintained by the device about the device or its logical units. It is a complementary
command to the log select command.
•
Mode select (15h). This command provides a means for the initiator to specify medium,
logical unit, or peripheral device parameters to the target. Targets that implement the
mode select command shall also implement the mode sense command.
•
Mode sense (1Ah). This command allows a target to report parameters to the initiator and
is a complementary command to the mode select command.
•
Read buffer (3Ch). This command is used in conjunction with the write buffer command
as a diagnostic function for testing target memory and the SCSI bus integrity.
•
Receive diagnostic results (1Ch). This command requests analysis data be sent to the ini-
tiator after completion of a send diagnostic.
•
Send diagnostic
(1Dh). This command requests the target to perform diagnostic opera-
tions on itself, on the logical unit, or on both.
•
Test unit ready
(00h). This command provides a means to check if the logical unit is
ready. This is not a request for a self-test. If the logical unit would accept an appropriate
medium-access command without returning check condition status, this command shall
return a good status.
•
Write buffer (3Bh). This command is used in conjunction with the read buffer command
as a diagnostic for testing target memory and the SCSI bus integrity.
7.8 Status
The status phase normally occurs at the end of a command (although in some cases may oc-
cur before transferring the command descriptor block). Figure 7.4 shows the format of the
status byte and Table 7.8 defines the status byte codes. This status byte is sent from the target
to the initiator during the status phase at the completion of each command unless the com-
mand is terminated by one of the following events:
•
Abort message.
•
Abort tag message.
•
Bus device reset message.
•
Clear queue message.
•
Hard reset condition.
•
Unexpected disconnect.
