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3.1 Control/Sense Commands
C141-E167 3 -
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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