IBM DJSA-210 - Travelstar 10 GB Hard Drive Specifications page 44

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.
DJSA-XXX supports a minimum of 20,000 emergency unloads.
6.4.6.2 Required Power-Off Sequence
The required BIOS sequence for removing power from DJSA-XXX is as follows:
! Step 1: Issue one of the following commands.
! Soft Reset
! 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 187.
! Step 3: Terminate power to HDD.
This power-down sequence should be followed for entry into any system power-down state, system
suspend state, or system hibernation state. In a robustly designed system, emergency unload is limited to
rare scenarios, such as battery removal during operation.
6.4.6.3 Power switch design considerations
In systems that use DJSA-XXX, consideration should be given to the design of the system power switch.
IBM recommends that the switch operate under control of the BIOS, as opposed to being hard-wired. The
same recommendation is made for cover-close switches. When a hard-wired switch is turned off,
emergency unload occurs, as well as the problems cited in section 5.1, "Data loss by power off" on
page 19 and section 5.2, "Write Cache" on page 19.
6.4.6.4 Test considerations
Start/stop testing is classically performed to verify head/disk durability. In the case of DJSA-XXX 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 DJSA-XXX invokes the emergency unload mechanism and subjects the HDD to
nontypical mechanical stress.
Power cycling testing may be required to test the boot-up function of the system. In this case IBM
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 30. Again, if this is not done, the emergency unload function is
invoked and nontypical stress results.
Travelstar 32GH/30GT/20GN hard disk drive specifications
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