Hitachi HTS548040M9AT00 Specifications page 40

• 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.
6.3.6.1 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 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.
6.3.6.2 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 187.
Step 3: Terminate power to the drive
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.
6.3.6.3 Power Switch design considerations
In systems that use this drive consideration should be given to the design of the system power switch.
Hitachi recommends that the switch operate under control of the BIOS rather than be hardwired. The same recom-
mendation is made for cover-close switches. When a hardwired switch is turned off, emergency unload occurs, as
well as the problems cited in Section 5.1, "Data loss at power off" on page 17 and Section 5.2, "Write Cache" on
page 17.
Travelstar 5K80 Hard Disk Drive Specification
26