Emergency Uload; Required Power-Off Sequence - Hitachi HTS541010G9AT00 - Travelstar 100 GB Hard Drive Specifications

• 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 emergency mode.
6.7 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 possible. 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 uncontrolled, it is
more mechanically stressful than a normal unload.
The drive supports a minimum of 20,000 emergency unloads.

6.7.1 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 fin-
ish completion; however, the BIOS time out value needs to be 30 seconds considering error recovery time. Refer to
section13.0 "Timings" on page 181.
Step 3: Terminate power to HDD.
6.7.1.1 Power witch design considerations
In systems that use the Travelstar 60GH & 40GN consideration should be given to the design of the system power
switch.
Hitachi recommends that the switch operate under control of the BIOS, as opposed to being hardwired. The same
recommendation is made for cover-close switches.When a hardwired switch is turned off, emergency unload
occurs, as well as the problems cited section "Data loss by power off."
6.7.1.2 Test Considerations
Start/stop testing is classically performed to verify head/disk durability. The heads do not land on the disk, so this
type of test should be viewed as a test of the load/unload function.
Start/Stop testing should be done by commands through the interface, not by power cycling the drive. Simple
power cycling of the drive invokes the emergency unload mechanism and subjects the HDD to nontypical mechan-
ical stress.
Power cycling testing may be required to test the boot-up function of the system. In this case Hitachi recommends
that the power-off portion of the cycle contain the sequence specified in section 6.4.6.2, "Required Power-Off
Sequence" on page 29. If this is not done, the emergency unload function is invoked and nontypical stress results.
Travelstar 5K100 (Serial ATA) Hard Disk Drive Specification
30