Specifications

If the drive supports reformatting of headers as well as data fields, the
data block is interpreted as shown in the following table:
DD15———-DD0 DD15———-DD0
First sector
descriptor
: : : :
Last sector
descriptor
Remainder of buffer
filled with zeros
One 16-bit word represents each sector, the words being contiguous
from the start of a sector. Any words remaining in the buffer after the
representation of the last sector are filled with zeros. Words DD15–8
contain the sector number. If an interleave is specified, the words appear
in the same sequence as they appear on the track. Words DD7–0 contain
a descriptor value defined as follows:
00
H
Format sector as good
20
H
Unassign the alternate location for this sector
40
H
Assign this sector to an alternate location
80
H
Format sector as bad
5.4.3 Identify Drive command
The Identify Drive command (command code EC
H
) transfers information
about the drive to the host. When the command is issued, the drive sets
BSY, prepares to transfer a single 512-byte block of data, sets DRQ, and
generates an interrupt. The host then reads the data from the drive. The
data is organized as shown in the table below. All reserved bits or words
are zero.
Words 53 to 59 and 62 to 63 change depending on the current operating
mode of the drive. All other words are constant for a particular drive.
An asterisk (*) indicates words for which a value of 0000
H
indicates
parameter not specified.
Identify Drive Command
Word Bit Description
0 15 0 = reserved for nonmagnetic drives
0 14 1 = format speed tolerance gap required
0 13 1 = track offset option available
0 12 1 = data strobe offset option available
40 ATA Interface Reference Manual, Rev. C