10.1.5 Unit Attention Condition
The file will generate a unit attention condition for each initiator whenever:
The file has been reset.
This includes Power On Reset, SCSI Bus Reset, SCSI BUS DEVICE RESET message.
The mode parameters in effect for this initiator has been changed by another initiator.
The microcode has been changed.
WRITE BUFFER command has been executed to download microcode. In this case, a unit attention
condition is generated for all initiators except the one that issued the command.
Commands are cleared by another initiator.
This condition is generated against the initiator that has queued commands, if ...
− Clear Queue Message is received.
− Contingent Allegiance Condition is cleared when QERR (in Mode Page 0A) is 1.
− DQue is set to 1 while queued command exist.
The unit attention condition persists for each initiator until that initiator clears the condition as described in
the following paragraphs.
If the file receives a command from each initiator before reporting a CHECK CONDITION status for a
pending unit attention condition for that initiator , the file's response varies with the command as follows.
INQUIRY The file executes the command with GOOD status and preserves the unit attention con-
dition.
REQUEST SENSE
If the file has an available pending sense data for the initiator, the file sends the pending
sense data and preserves the unit attention condition for the initiator.
If the file does not have an available pending sense data for the initiator, the file sends
sense data for the unit attention condition and clears the unit attention condition for the
initiator.
ALL OTHER The file terminates the command with a CHECK CONDITION status and preserves
the unit attention condition.
If the file receives a command from each initiator after reporting a CHECK CONDITION status for a
pending unit attention condition for that initiator , the file's response varies with the command as follows.
REQUEST SENSE The file sends the sense data for a pending unit attention condition and returns GOOD
status. And the file clears the unit attention condition for the initiator.
ALL OTHER The file executes the command with GOOD status and clears the unit attention condi-
tion unless another unit attention condition exists. And then the sense data for the unit
attention condition is lost.
10.1.6 Command Processing During Start-up and Format Operations
If the Target receives a command from an Initiator while the Target is executing a start-up or format opera-
tion, The Target's response varies with the command as follows:
INQUIRY The file sends inquiry data and returns appropriate status.
Additional Information 183
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