Table of Contents
Advertisement
1.5
UNIT ATTENTION Condition
The UNIT ATTENTION condition is a function used to notify the INIT asynchronously of an
event (status change) that has occurred in the TARG or logical unit.
1.5.1
Generation of the UNIT ATTENTION Condition
Events which cause a UNIT ATTENTION condition to be generated are one of the following.
(1)
When Power on, RESET or BUS DEVICE RESET occurs
If the IDD's power is switched on, enters the RESET condition or is reset by a BUS DEVICE
RESET message, this UNIT ATTENTION condition is generated for all the INITs, regardless
of whether the disk drive is in the ready state or not.
(2)
Mode parameters changed (If changed by another INIT)
If the following parameters specified in the MODE SELECT or MODE SELECT EXTENDED
commands are changed by any INIT, a UNIT ATTENTION condition is generated for al the
INITs other than the INIT which changed the parameters.
–
Parameters related to the data format (block descriptor, Page 3: format parameters, Page 4:
drive parameters, any one)
–
Parameters related to the cache segment (Page 8: caching parameter, byte 13)
–
Parameters related to command queuing (Page A: Except the RLEC bit of byte 3 of the
control mode parameter)
(3)
Commands cleared by another INIT
Commands which are being executed or which are queued are cleared if the following events
occur, and this UNIT ATTENTION condition is generated.
•
If the CLEAR QUEUE message is issued by any INIT.
•
If tagged queuing is prohibited in a MODE SELECT or MODE SELECT EXTENDED
command (Page A send) from any INIT. (DQue = "1")
•
If the sense hold state of an INIT is canceled when "1" is specified in the QErr bit of
MODE SELECT parameter page A.
However, the IDD does not enter the UNIT ATTENTION condition hold state for an INIT that
issues a CLEAR QUEUE message, an INIT that issues a MODE SELECT or MODE SELECT
EXTENDED command, or an INIT that cancels the sense hold state.
C141-E039-01EN
1 - 23
Advertisement
Table of Contents
