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Command Processing
1 - 22 C141-E167
The IDD executes the REQUEST SENSE command normally and sends the sense data which
indicate the UNIT ATTENTION condition and are being held to the INIT. At this time, the
UNIT ATTENTION condition for that INIT is cleared.
1.5.3 UNIT ATTENTION condition multiple hold
If any UNIT ATTENTION condition is generated and a new UNIT ATTENTION condition is
generated for a different reason before the INIT for which the first UNIT ATTENTION condition
was held clears it, those UNIT ATTENTION conditions are held together, and the IDD reports these
multiple UNIT ATTENTION conditions in sequence. For example, a “Mode parameters changed,”
“Spindle Synchronized” or “Spindle not Synchronized” or other UNIT ATTENTION condition may
be reported after the “Power on, RESET or TARGET RESET occurred” UNIT ATTENTION
condition is reported.
1.6 Sense Data Hold State
1.6.1 Sense data hold condition
The IDD generates sense data if any of the following conditions occurs and enters the sense data hold
state until the conditions for cancellation, described in Section 1.6.2, are established. The sense data
which are generated, are held for each individual INIT that issued the applicable command. The
sense data hold state is also maintained individually for each INIT which is their object.
1) If the IDD reports a CHECK CONDITION status, sense data is generated for the command that
was terminated by the CHECK CONDITION status.
2) If a fatal error occurs on the SCSI bus and the IDD forcibly enters the BUS FREE phase, sense
data is generated for the command that was being executed on the SCSI bus. However, if the
LUN cannot be identified by the point when the error occurs, the IDD does not generate sense
data.
3) Since it is impossible for reconnection processing to be executed without a response from the
INIT in the RESELECTION phase, if the IDD clears the command that is necessary for
reconnection processing, sense data is generated for that command.
Notes:
1. In the case of 3) above, the IDD does not clearly inform the INIT of the occurrence of an
error, but terminates the command abnormally and enters the sense data hold state. If a long
period of time passes with no response from the IDD, the INIT that issued the command
should issue a REQUEST SENSE command and confirm the content of the error.
2. If the INIT which is the object of holding of sense data cannot be identified because the
INIT’s SCSI ID was not notified in the SELECTION phase, the INIT enters an unspecified
special sense data hold state. In this case, the IDD regards this as the INIT that is the object
of holding of the sense data starting a new SELECTION phase in which the INIT’s SCSI ID
is not notified.
1.6.2 Response and release conditions at sense data hold state
The response of the IDD when it receives a new command while it is in the sense data hold state, and
conditions for releasing the sense data hold state are shown below.