Request Sense Command - Sony CDU-541 Interface Manual

CDU-541 CD-ROM DRIVE SCSI INTERFACE MANUAL
5 .2.27. REQUEST SENSE Command
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Bitl
Byte
I
7
6
5
4
3
2 1
a
==============================================================================
o
I
Operation Code (03h)
I
-----1-----------------------------------------------------------------------1
1 :
Logical Unit Number: Reserved
I
-----1-----------------------------------------------------------------------1
2 :
Reserved
I
-----1-----------------------------------------------------------------------1
3
I
Reserved
I
-----\-----------------------------------------------------------------------1
4 :
Allocation Length
I
-----1-----------------------------------------------------------------------1
5 I
Control Byte
I
==============================================================================
The REQUEST SENSE command requests that the controller transfer sense data
to the initiator.
The sense data will be valid after a CHECK CONDITION status has been
returned on the previous command. This sense data will be preserved by the
controller for the initiator until
1)
it is retrieved by a REQUEST SENSE command from that initiator.
2)
the receipt of
~~other
command for the same logical unit from that
initiator.
3)
a reset condition occurs.
Note: The sense data will be cleared upon receipt of any subsequent
command for the same logical unit from the initiator that was returned the
CHECK CONDITION status. See Section
4.1.3.
The REQUEST SENSE command will return the CHECK CONDITION status only to
report catastrophic errors for the REQUEST SENSE command. Following a
catastrophic error on a REQUEST
SS~SE
command, sense data may be invalid. For
example:
1)
A reserved bit is set the command descriptor block.
2)
An unrecovered parity error occurs on the bus.
3)
A controller malfunction prevents return of the sense data.
If an error occurs during the execution of the REQUEST SENSE command, but it
is not catastrophic, the controller will return the sense data with GOOD
status.
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