Fujitsu MAX3073NC - SCSI,80, Dell DC961,Hard Drive Scsi Logical Interface Specifications page 111

The length of the sense data in the IDD is 48 bytes. The "Transfer byte length" field in the CDB
indicates the number of bytes of sense data which can be received by the INIT. The IDD transfers sense
data to the INIT by either of the following two methods, depending on the specification in the CHANGE
DEFINITION command (SCSI level). Furthermore, see Section 3.1.4 (SCSI Level) concerning the
CHANGE DEFINITION command.
•
If the SCSI-3/SCSI-2 mode is specified in the CHANGE DEFINITION command, the IDD
transfers the number of bytes of sense data specified in the "Transfer byte length" field or the
number of bytes in the sense data held by the IDD (48 bytes), whichever is smaller, to the INIT.
When zero is specified in the "Transfer byte length" field, this command is terminated with
nothing transferred, but in this cases also, the sense data held by the IDD are cleared.
•
If SCSI-1/CCS Mode is specified in the CHANGE DEFINITION command, when zero is
specified in the "Transfer byte length" field, the IDD transfers to the INIT only 4 bytes of sense
data, from the top. When a value other than zero is specified in the "Transfer byte length" field,
the IDD transfers to the INIT the number of bytes of sense data specified in the "Transfer byte
length" field or the length of sense data held by the IDD (48 bytes), whichever is smaller.
As described in Section 1.6 "Sense Data Hold State," if the IDD terminates a command which it is
currently executing abnormally, it generates sense data for the INIT that issued that command and
maintains those sense data in the hold state.
Sense data are held in a valid state until they are read by a REQUEST SENSE command from the INIT
for which they are held. However, sense data which are being held are cleared by an ABORT TASK
SET message from the INIT for which they are held, a TARGET RESET message or CLEAR TASK
SET message from any INIT, or a RESET condition.
If a command is terminated with a CHECK CONDITION status, when the SCSI bus enters the BUS FREE
phase unintentionally during execution of a command, or when the INIT detects that there is no reconnection
request from the IDD, the INIT should issue this command and fetch the sense data.
Note:
See Section 1.6, "Sense Data Hold State" concerning details of the sense data hold state and see
Section 5.1, "Sense Data" concerning the format of sense data transferred by this command from the
IDD to the INIT, and its contents.
If this command is issued while the IDD is holding the UNIT ATTENTION condition, if the IDD is not
in the sense data hold state at that point, sense data indicating the UNIT ATTENTION condition are sent
to the INIT by this command and the UNIT ATTENTION condition is cleared. For details, see Section
1.5, "UNIT ATTENTION Condition."
If this command is issued when valid sense data are not being held, the IDD sends the sense key "NO
SENSE[=0]" with sense data showing the message "No additional sense information [=00-00]" to the
INIT.
This command is terminated abnormally with a CHECK CONDITION status reported only when the
conditions shown below are detected. In this case, new sense data are generated and the sense data
which had been held up to that point are lost.
•
An error in a specification other than the LUN field of the CDB
•
Sense data cannot be sent due to a hardware error in the IDD
•
An unrecoverable error is detected on the SCSI bus.
C141-C010
3.1 Control/Sense Commands
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