At Interface; Command Set - Seagate ST3780A Product Manual

Medalist Family AT Product Manual, Rev. A

3.0 AT interface

The AT interface implemented on these drives is compatible with the
requirements of the IBM AT bus. The AT interface consists of single-
ended, TTL-compatible receivers and drivers communicating through a
40-conductor flat-ribbon, nonshielded cable with a maximum length of
18 inches (0.46 meters) using an asynchronous interface protocol. The
drivers can sink up to 24 mA and drive a load up to 300 pF.

3.1 Command set

This section lists all ATA commands implemented in the ST31220 family
drives and describes certain commands in detail. Some commands, as
mentioned in the text, supplement the standard ATA commands. For a
complete description of all AT interface commands, refer to the Seagate
ATA Interface Reference Manual , part number 36111- xxx . Additional
information on Fast ATA-related features is provided by the Small Form
Factor specification, SFF-8011 Rev 1.1, September 18, 1993.
The Set Features command and the Sleep command, described in the
Seagate ATA Interface Reference Manual , require further elaboration.
These commands are described in Section 3.1.2 and 3.1.3.
The table on page 24 lists all commands implemented in the ST31220
family drives. The table uses the following abbreviations:
FR Features register
SC Sector Count register
SN Sector Number register
CY Cylinder register
DH Drive/Head register
n This register does not contain a valid parameter for this
command.
y This register contains a valid parameter for this command. In
the Drive/Head register, both the drive and head parameters
are valid for this command.
D The Drive/Head register contains a valid drive parameter for
this command. The head parameter is not valid for this
command.
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