I have a question of the intent of the Power Condition mode parameters.

The following text is from SPC-4r16.
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7.4.12 Power Condition mode page

The Power Condition mode page provides an application client with methods to control the power condition of a
logical unit (see 5.10). These methods include:
a) Specifying that the logical unit transition to a power condition without delay; and
b) Activating and setting of idle condition and standby condition timers to specify that the logical unit wait for a period of inactivity before transitioning to a specified power condition.
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Item a) implies to me that there is a method of telling the target to "go to specified power condition immediately (i.e., now)".
Item b) implies to me that there is a method of specifying a timer value for when to transition to the power condition.

Is the intent of listing a) separately to infer that a timer value of zero is the "go immediately" command and that it is a one time event?  Or is the intent that the timer value is modified to be zero and the side effect of that modification is that the power condition is immediately transitioned to?  Stated differently, does a mode select specifying a power condition timer of zero modify that timer until the next mode select (or event that changes mode parameters) thereby causing a device to transition out of and back into that state on the receipt and completion of each command that causes a transition (e.g., write)?

Thanks,

Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt@us.ibm.com
http://www-03.ibm.com/servers/storage/