IBM IC35L040AVVN07-0 Hard Drive Specifications - Page 90

Sector Addressing Mode

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9.4 Sector Addressing Mode All addressing of data sectors recorded on the drive media is 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 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. 9.4.1 Logical CHS Addressing Mode The logical CHS addressing is made up of three fields: cylinder number, head number and 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 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 translation mode is also described in the Identify Device Information. 9.4.2 LBA Addressing Mode Logical sectors on the device shall 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 x heads per cylinder + heads) x 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

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9.4 Sector Addressing Mode
All addressing of data sectors recorded on the drive media is 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 address-
ing 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.
9.4.1 Logical CHS Addressing Mode
The logical CHS addressing is made up of three fields: cylinder number, head number and 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 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 is also described in the Identify Device Information.
9.4.2 LBA Addressing Mode
Logical sectors on the device shall 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 x heads per cylinder + heads) x 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 120GXP hard disk drive specifications
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