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Western Digital Hard Disk Drive OEM Specification
11.12 Idle (E3h/97h)
Command Block Output Registers
Command Block Input Registers
Table 123 Idle Command (E3h/97h)
The Idle command causes the device to enter Idle mode immediately, and set auto power down timeout parameter
(standby timer). And then the timer starts counting down.
When the Idle mode is entered, the device is spun up to operating speed. If the device is already spinning, the spin
up sequence is not executed.
During Idle mode the device is spinning and ready to respond to host commands immediately.
Output Parameters To The Device
Timeout Parameter. If zero, then the automatic power down sequence is disabled. If non-zero,
then the automatic power down sequence is enabled, and the timeout interval is shown below:
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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.