Hitachi HDS721050CLA362 Specifications page 139

Output Parameters To The Device
Sector Count Timeout Parameter.
non-zero, then the automatic power down sequence is enabled, and the timeout interval is
shown below:
When the automatic power down sequence is enabled, the drive will enter Standby mode
automatically if the timeout interval expires with no drive access from the host. The timeout
interval will be reinitialized if there is a drive access before the timeout interval expires.
HITACHI Deskstar & CinemaStar 7K1000.B & Deskstar E7K1000 Hard Disk Drive specification
If zero, then the automatic power down sequence is disabled. If
241-251
135
Value Timeout
---------- -------------------------
0 Timer disabled
1-240 Value * 5
(Value-240) * 30 minutes
252 21 minutes
253 8 hours
254 21 minutes 10 seconds
255 21 minutes 15 seconds