Specifications

5.0 ATA interface commands

All ATA commands are decoded from the command register in the

command block. The host sets up all necessary parameters and enables

INTRQ (if used by the host) through other registers of the command block

before the command code is written to the command register. The drive

begins to execute a command immediately after the command register

is written. Upon completion of the command, the drive returns valid status

information through the Status register. If the error bit in the Status

When two drives are daisy-chained on a single interface, commands are

sent to both drives. In most cases, only the selected drive executes the

command. The desired drive is selected through the drive bit in the

Drive/Head register.

The host can program the drive to perform commands and report its

status to the host after the completion of each command. In the case of

a diagnostic command, both drives execute the command. The slave

reports to the master that it has completed the diagnostic command using

the PDIAG– signal. For all other commands, only the selected drive

executes the command.

Note. Some ATA commands are optional and may not be supported by

all drives. See the appropriate Seagate product manual, which

will identify any of the following commands that may not be

supported by a particular drive model.

5.1 Logical block addressing

Some Seagate drives can operate in either standard cylinder-head-sec-

tor (CHS) or logical block addressing (LBA) mode, on a command-by-

command basis. A drive that supports LBA indicates this through word

49, bit 9 of the Identify Drive information. If the host selects LBA (by

setting bit 6 of the Drive/Head register), then the sectors on the drive are

assumed to be linearly mapped, with an LBA 0 of cylinder 0 / head 0 /

sector 1.

Seagate drives that support logical block addressing have the following

characteristics:

• The data returned from the Identify Drive command changes as

described below:

– Bit 9 in Word 49 is set to 1, and

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