SpinPoint Barracuda Series, Product Manual

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Barracuda Product Manual Rev04
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SQUELCH
-This block establishes a limit so that detection of a common mode signal can be properly
accomplished.
WORD-
A word is sixteen (16) bits of data. A word may be represented as 16 bits or as two adjacent bytes.
When shown as bits the least significant bit is bit 0 and most significant bit is bit 15. The most significant bit
is shown on the left. When shown as bytes the least significant byte (lower) byte is byte 0 and the most
significant byte (upper) byte is byte 1.
6.2 Physical Interface
For information please consult the document entitled “Serial ATA Revision 2.5” released on October 27,
2005 available from the Internet http://www.sata-io.org/ still retrievable on May 11, 2006. Section 7 of the
document contains physical layer specifications related topics.
6.3 Signal Summary
For details, please consult the document entitled “Serial ATA Revision 2.5” released on October 27, 2005
available from the Internet http://www.sata-io.org/ still retrievable on May 11, 2006.
6.3.1 Signal Descriptions
For data packets and additional information please consult the document entitled “Serial ATA Revision 2.5”
released on October 27, 2005 available from the Internet http://www.sata-io.org/ still retrievable on May 11,
2006.
A device can operate in either of two addressing modes, CHS or LBA, on a command-by-command basis.
The CHS mode is supported for legacy command access only. The task file registers contains the Cylinder,
Head, and Sector information of a requested location. Because the disk drive has its own mapping, the CHS
mode is translated into disk drive physical address by the HDD firmware. There is no direct relationship of
the CHS that can be accessed from the host.
This CHS term defines the addressing mode of the device as being by physical sector address. The physical
sector address is made up of three fields: the sector number, the head number and the cylinder number.
Sectors are numbered from 1 to a device specific maximum value, which cannot exceed 255. Heads are
numbered from 0 to a device specific maximum value, which cannot exceed 15. Cylinders are numbered
from 0 to a device specific maximum value, which cannot exceed 65,535. Typically, sequential access to the
media is accomplished by treating the sector number as the least significant portion, the head number as the
mid portion, and the cylinder number as the most significant portion of the CHS address.
In LBA mode the sectors on the device are assumed to be linearly mapped with an initial definition of: LBA
0 = (Cylinder 0, head 0, and sector 1). Irrespective of translate mode geometry set by the host, the LBA
address of a given sector does not change: