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2.5
UNIT ATTENTION Condition
The Unit Attention condition is a function for notifying the INIT asynchronously of events
(status changes) which occur in the TARG or logical unit.
2.5.1
Generation of the UNIT ATTENTION condition
Events which cause the Unit Attention condition to be generated are any of the following
events.
(1)
When a Power On, LIP (YX), PRLI or TARGET RESET occurs.
If the IDD is reset by a power on, LIP (YX), PRLI or TARGET RESET, regardless of whether
the disk drive is in the ready state or not, the Unit Attention condition is generated to all the
INITs.
(2)
Mode parameters changed (if changed by another INIT)
If any of the following parameters specified by the MODE SELECT or MODE SELECT
EXTENDED command are changed by any INIT, the Unit Attention conditions is generated
toward all the INITs except the INIT that changed that parameter.
–
Parameters related to the data format (block descriptor, page 3: format parameter, page 4:
any drive parameter)
–
Parameters related to the cache segment (page 8: Caching parameter, byte 13)
–
Parameters related to command queuing (page A: control mode parameter, except the
RLEC bit in byte 3)
(3)
Commands cleared by another INIT
If the following events have occurred, the command which is currently being executed and
commands in the queue are cleared, and this Unit Attention condition is generated.
•
The CLEAR TASK SET message is issued by any INIT.
However, the Unit Attention condition hold state is not entered in the INIT that issued the
CLEAR TASK SET, the INIT that issued the MODE SELECT or MODE SELECT
EXTENDED command or the INIT that canceled the sense hold state.
2.5.2
Response and Release Condition at UNIT ATTENTION Condition Hold State
A Unit Attention condition generated by the IDD due to the occurrence of one of the above-
mentioned events is held for each INIT individually, and this condition is held until the Unit
Attention condition is cleared by an INIT which is the object of the hold issues the commands
specified below.
When the IDD is holding the Unit Attention condition, if it receives a command from an INIT
which is the object of the hold, one of the operations below, depending on the type of
command issued, is performed by the IDD.
C141-E054-02EN
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