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Command Processing
1 - 20 C141-E167
(1) When power on, RESET or TARGET RESET occurs
If the IDD’s power is switched on, the IDD enters the RESET condition or is reset by a TARGET
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 (changed by another INIT)
If the parameters specified in the MODE SELECT or MODE SELECT EXTENDED command are
changed by any INIT, a UNIT ATTENTION condition is generated for all the INITs other than the
INIT which changed the parameters.
(3) Commands cleared by another INIT
Commands which are being executed or which are queued are cleared if one of the following events
occurs, and this UNIT ATTENTION condition is generated.
• The CLEAR TASK SET message is issued by any INIT.
• Tagged queuing is prohibited by a MODE SELECT or MODE SELECT EXTENDED command
(Page A send) from any INIT. (DQue = “1”)
• The sense hold state of an INIT is released 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 TASK SET message, an INIT that issues a MODE SELECT or MODE SELECT
EXTENDED command, or an INIT that releases the sense hold state.
(4) Changed operating definition
When the operation mode is changed by the CHANGE DEFINITION command, the UNIT
ATTENTION condition is generated for all INITs.
1.5.2 Response and release condition at UNIT ATTENTION condition hold state
A UNIT ATTENTION condition generated by the IDD by the occurrence of the previously
mentioned events is held individually for each INIT and it is held until it is released by the INIT it is
held for issuing the commands specified below.
When the IDD is holding a UNIT ATTENTION condition, if the IDD receives a command from the
INIT that the UNIT ATTENTION condition is held for, it performs one of the following operations
depending on the type of command issued.
(1) Commands other than the INQUIRY and REQUEST SENSE commands
The IDD reports a CHECK CONDITION status to the issue command. The UNIT ATTENTION
condition for that INIT is then cleared by the CHECK CONDITION status report. The sense key of the
sense data generated at this time is UNIT ATTENTION [=6] and the sense codes shown below indicate the
event that generated the UNIT ATTENTION condition.