SAT TEST UNIT READY command translation

Douglas Gilbert dougg at
Fri Aug 12 19:42:43 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* Douglas Gilbert <dougg at>
Sheffield, Robert L wrote:
> There is a proposal in-process to redefine the Test Unit Ready
> translation in SAT:
> See the SAT WG agenda:

Those references do not mention the TEST UNIT READY command
but the closely related START STOP UNIT command.

SAT revision 5 ties the implementations of those two commands
together, so perhaps Mark Evan's proposal to change
the START STOP UNIT command in SAT could be extended to
cover the TEST UNIT READY command (and REQUEST SENSE, see

> In this proposal - if the device is in standby the SATL issues the
> command anyway. If it completes without error - GOOD status is returned.

If you are proposing that TEST UNIT READY still translates
to the Check Power Mode ATA command and returns a SCSI
status of GOOD unless that ATA command fails, then that
seems reasonable.

I just noticed that REQUEST SENSE in SAT (rev 05) does
yield a sense key of NO SENSE and an additional sense
code of LOW POWER CONDITION ON when the ATA disk is
in Standby power mode. Perhaps a note could be added
about how the SAT layer comes to this conclusion (i.e.
issues a Check Power Mode ATA command).


cc-ed to Mark Evans

Doug Gilbert
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