Unit attention after block descriptor

Alan Dayley adayley at adtron.com
Thu Jun 7 14:52:10 PDT 2001

* From the T10 Reflector (t10 at t10.org), posted by:
* Alan Dayley <adayley at adtron.com>

I need clarified two parts of the SCSI-2 specification.

Section "8.3.3 Mode parameters", paragraph right after "Table 93 - Mode
parameter block descriptor", the last sentence states:

"A unit attention condition (see 7.9) shall be generated when any block
descriptor values are changed."

UNDERSTANDING 1: To me this means "Generate a unit attention when block
descriptor values are changed. Always. For all initiators. All of them."

Section "7.9 Unit attention condition" describes the events which generate
a unit attention condition.  Event "b)" states:

"b) The mode paramters in effect for this initiator have been changed by
another initiator;"

Note the terms "this initiator" and "another initiator."

UNDERSTANDING 2: To me this means "Generate a unit attention for initiator
A (this initiator) if initiator B (another initiator) changed the mode
paramters.  Initiator B does not need a unit attention because he made the

Assuming UNDERSTANDING 2 is correct, that would mean that in a one
initiator, one target system a unit attention does NOT need to be generated
when the one initiator changes mode parameters.  But that violates
UNDERSTANDING 1 that mode parameter changes always generate unit attention
for all initiators.

So, finally, my question: is UNDERSTANDING 1 correct or UNDERSTANDING 2
correct or am I not UNDERSTANDING?  ;^)


|Alan Dayley             www.adtron.com
|Software Engineer       602-735-0300 x331
|ADayley at adtron.com
|Adtron Corporation         
|3710 E. University Drive, Suite 5
|Phoenix, AZ  85034

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