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6.4.5 Preventive maintenance
None.
6.4.6 Load/unload
The product supports a minimum of 300,000 normal load/unloads.
Load/unload is a functional mechanism of the hard disk drive. It is controlled by the drive micro code.
Specifically, unloading of the heads is invoked by the following commands:
! Hard reset
! Standby
! Standby immediate
! Sleep
Load/unload is also invoked as one of the idle modes of the drive.
The specified start/stop life of the product assumes that load/unload is operated normally, not in emergen-
cy mode.
6.4.6.1 Emergency unload
When hard disk drive power is interrupted while the heads are still loaded the micro code cannot operate
and the normal 5-volt power is unavailable to unload the heads. In this case, normal unload is not possi-
ble. The heads are unloaded by routing the back EMF of the spinning motor to the voice coil. The actuator
velocity is greater than the normal case and the unload process is inherently less controllable without a
normal seek current profile.
Emergency unload is intended to be invoked in rare situations. Because this operation is inherently uncon-
trolled, it is more mechanically stressful than a normal unload.
The drive supports a minimum of 20,000 emergency unloads.
6.4.6.2 Required Power-Off Sequence
The required BIOS sequence for removing power from the drive is as follows:
! Step 1: Issue one of the following commands.
! Standby
! Standby immediate
! Sleep
Note: Do not use the Flush Cache command for the power off sequence because this command
does not invoke Unload.
! Step 2: Wait until the Command Complete status is returned.
In a typical case 350 ms are required for the command to finish completion; however, the BIOS time
out value needs to be 30 seconds considering error recovery time. Refer to section 14.0, "Time-out
values," on page 195.
! Step 3: Terminate power to HDD.
Hitachi Travelstar 60GH & 40GN hard disk drive specifications
29
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