HGST Travelstar 7K500 BE, 250GB 0A79102 ユーザーズマニュアル

製品コード

0A79102

7K500 OEM Specification

Page 53 of 176

12.3

12.3 Power

Power

Power----off considerations

off considerations

12.3.1

Load/Unload

Load/Unload is a functional mechanism of the HDD. It is controlled by the drive microcode.
Specifically, unloading of the heads is invoked by the commands:

Command

Response

Standby

UL -> Comp.

Standby immediate

UL -> Comp.

Sleep

UL -> Comp.

“UL” means “unload”.

“Comp” means “complete”.

Table 33 Device’s behavior by ATA commands

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.

12.3.2

Emergency unload

When HDD power is interrupted while the heads are still loaded, the microcode cannot operate and
the normal 5V power is unavailable to unload the heads. In this case, normal unload is not possible,
so  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.

A single emergency unload operation is more stressful than 100 normal unloads. Use of emergency
unload reduces the start/stop life of the HDD at a rate at least 100X faster than that of normal
unload, and may damage the HDD.

12.3.3

Required power

Required power----off sequence

off sequence

Problems can occur on most HDDs when power is removed at an arbitrary time. Examples:

Data loss from the write buffer.
If the drive is writing a sector, a partially-written sector with an incorrect ECC block results. The sector

contents are destroyed and reading that sector results in a hard error.

Heads possibly land in the data zone instead of landing zone, depending on the design of the HDD.

You may then turn off the HDD in the following order:

1.  Issue Standby Immediate or sleep command.
2.  Wait until COMMAND COMPLETE STATUS is returned. (It may take up to 350 ms in typical case)
3.  Terminate power to HDD.

This power-down sequence should be followed for entry into any system power-down state, or 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.

12.4

12.4 Sector Addressing Mode

Sector Addressing Mode

All  addressing  of  data  sectors  recorded  on  the  device’s  media  is  by  a  logical  sector  address.  The
logical  CHS  address  for  HTS7250XXA9A3XX  is  different  from  the  actual  physical  CHS  location  of
the data sector on the disk media.