Logical Chs Addressing Mode; Lba Addressing Mode; Sector Addressing Mode - Hitachi HDS723020BLA642 Specifications

9.3

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 HDS7230xxBLA642 / HDS5C30xxALA632 / HCS5C20xxALA632 is different from the actual
physical CHS location of the data sector on the disk media. All addressing of data sectors recorded on the
device's media.
HDS7230xxBLA642 / HDS5C30xxALA632 / HCS5C20xxALA632 support both Logical CHS Addressing Mode
and LBA Addressing Mode as the sector addressing 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. So a host system must set the L
bit to 1 if the host uses LBA Addressing mode.
9.3.1

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 translation mode but
can not exceed 255(0FFh). Heads are numbered from 0 to the maximum value allowed by the current CHS
translation mode but can not 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 translation
mode also is described in the Identify Device Information.
9.3.2

LBA Addressing Mode

Logical sectors on the device shall be linearly mapped with the first LBA addressed sector (sector 0) being the
same sector as the first logical CHS addressed sector (cylinder 0, head 0, sector 1). Irrespective of the logical
CHS translation mode currently in effect, the LBA address of a given logical sector does not change. The
following is always true:
LBA = ( (cylinder * heads_per_cylinder + heads)
* sectors_per_track ) + sector - 1
where heads_per_cylinder and sectors_per_track are the current translation mode values.
On LBA addressing mode, the LBA value is set to the following register.
Device/Head
Cylinder High
Cylinder Low
Sector Number
<--- LBA 27-24
bits
<--- LBA 23-16
bits
<--- LBA 15- 8
bits
<--- LBA 7- 0
bits
Hitachi hard disk drive specifications
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