IBM DTCA-24090 Hard Drive Specifications - Page 79

Sector Addressing Mode

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10.3 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 DTCA-2xxxx/DPLA-2xxxx is different from the actual physical CHS location of the data sector on the disk media. DTCA-2xxxx/DPLA-2xxxx 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. 10.3.1 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. 10.3.2 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

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10.3 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 DTCA-2xxxx/DPLA-2xxxx is different from the actual physical CHS location of the data sector
on the disk media.
DTCA-2xxxx/DPLA-2xxxx 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.
10.3.1
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 trans-
lation mode also is described in the Identify Device Information.
10.3.2
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
<---
LBA bits 27-24
Cylinder High
<---
LBA bits 23-16
Cylinder Low
<---
LBA bits 15- 8
Sector Number
<---
LBA bits 7- 0
General Operation Descriptions
71