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11.4.3 Required power-off sequence
When power is removed on most drives at an arbitrary time, problems can result. The followoing are
examples of such problems:
!
Data is lost 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 may land in the data zone instead of the landing zone depending on the design of the drive
You may then turn off the drive 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 a typical
case.)
3. Terminate power to 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.
11.5 Sector Addressing Mode
All addressing of data sectors recorded on the device's media is done by a logical sector address. The
logical CHS address for the drive is different from the actual physical CHS location of the data sector on
the disk media.
The drive supports both Logical CHS Addressing Mode and LBA Addressing Mode as the sector addres-
sing mode.
The host system may select either the currently selected CHS translation addressing or LBA addressing
on a command-by-command basis by using the L bit in the DEVICE/HEAD register. A host system must
set the L bit to 1 if the host uses LBA Addressing mode.
11.5.1 Logical CHS addressing mode
The logical CHS addressing is made up of three fields: the cylinder number, the head number, and the
sector number. Sectors are numbered from 1 to the maximum value allowed by the current CHS trans-
lation mode but cannot exceed 255 (0FFh). Heads are numbered from 0 to the maximum value allowed by
the current CHS translation mode but cannot exceed 15 (0Fh). Cylinders are numbered from 0 to the
maximum value allowed by the current CHS translation mode but cannot exceed 65535 (0FFFFh).
When the host selects a CHS translation mode using the INITIALIZE DEVICE PARAMETERS command,
the host requests the number of sectors per logical track and the number of heads per logical cylinder.
The device then computes the number of logical cylinders available in requested mode.
The default CHS translation mode is described in the Identify Device Information. The current CHS trans-
lation mode also is described in the Identify Device Information.
Hitachi Travelstar 60GH & 40GN hard disk drive specifications
78
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