Sector Addressing Mode | Hitachi HCS721016CLA382, HCS721050CLA382

9.3Sector Addressing Mode

All addressing of data sectors recorded on the device's media is by a logical sector address. The logical CHS address for HDS7210xxCLA3yz / HUA7220xxCLA33z / HCS5C10xxCLA382 / HCS7210xxCLA3y2 / HDS5C10xxCLA382 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.

HDS7210xxCLA3yz / HUA7220xxCLA33z / HCS5C10xxCLA382 / HCS7210xxCLA3y2 / HDS5C10xxCLA382 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	<---	LBA	27-24
		bits
Cylinder High	<---	LBA	23-16
		bits
Cylinder Low	<---	LBA	15- 8
		bits
Sector Number	<---	LBA	7- 0
		bits

Hitachi hard disk drive specifications

HCS721016CLA382, HCS721050CLA382, HCS721025CLA382, HDP725050GLA360, HUA722050CLA330/1 specifications

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