Specifications

Identify Drive Command
Word Bit Description
53 0 1 = the fields reported in words 54–58 are valid;
0 = the fields reported in words 54–58 are not valid
54 — Number of current cylinders
(the number of user-addressable cylinders in
the current translation mode; not valid unless bit
0 of word 53 is set to 1)
55 — Number of current heads
(the number of user-addressable heads in the
current translation mode; not valid unless bit 0
of word 53 is set to 1)
56 — Number of current sectors per track
(the number of user-addressable sectors per
track in the current translation mode; not valid
unless bit 0 of word 53 is set to 1)
57–58 — Current capacity in sectors
(the current capacity in sectors excludes all
sectors used for device-specific purposes. The
number of sectors of available capacity is
calculated as: (
Number of current cylinders ) ×
(
Number of current heads ) × ( Number of current
sectors per track
); not valid unless bit 0 of word
53 is set to 1)
59 15–9 ATA reserved (should be zero)
59 8 1 = Multiple sector setting is valid
59 7–0 Number of sectors transfered during Read/Write
Multiple commands (xx
H
= Current setting for
number of sectors that can be transferred per
interrupt on Read Multiple and Write Multiple
commands; only applies if the valid bit [bit 8] is
set to 1)
continued from previous page
44 ATA Interface Reference Manual, Rev. C