13.4 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 all models is different from the actual physical CHS location of the data sector on the
disk media.
All models of the drive 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. A host system must
set the L bit to 1 if the host uses the LBA Addressing mode.
13.4.1 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 cannot exceed 255 (0FFh). Heads are numbered from zero to the maximum value
allowed by the current CHS translation mode but cannot exceed 15 (0Fh). Cylinders are numbered from
zero 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 is also described in the Identify Device Information.
13.4.2 LBA Addressing Mode
Logical sectors on the device must be mapped linearly 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).
Regardless of the logical CHS translation mode currently in effect, the LBA address of a given logical
sector does not change. The following formula is always true:
LBA = ((cylinder * heads per cy 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
<--- LBA bits 27–24
Cylinder High <--- LBA bits 23–16
Cylinder Low
<--- LBA bits 15– 8
Sector Number <--- LBA bits 7– 0
Deskstar 60 GXP Hard disk drive specification
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Содержание IC35L020 - Deskstar 20 GB Hard Drive
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