91
Western Digital Hard Disk Drive OEM Specification
Byte
Size
Field Name
Description
1:0
Word
Format Version
Data table format version (=0002h)
3:2
Word
Sampling Period
Absolute HDA Temperature sampling period in minutes.
0000h indicates sampling is disabled.
5:4
Word
Interval
Timer interval between entries in the history queue.
6
Byte
Max Op Limit
Maximum recommended continuous operating temperature. This is a
one byte 2’s complement number that allows a range from -127°C to
+127°C to be specified. 80h is an invalid value. This is a fixed value.
7
Byte
Over Limit
Maximum temperature limit. This is a one byte 2’s complement
number that allows a range from -127°C to +127°C to be specified.
80h is an invalid value. This is a fixed value.
8
Byte
Min Op Limit
Minimum recommended continuous operating limit. This is a one byte
2’s complement number that allows a range from -127°C to +127°C to
be specified. 80h is an invalid value. This is a fixed value.
9
Byte
Under Limit
Minimum temperature limit. This is a one byte 2’s complement number
that allows a range from -127°C to +127°C to be specified. 80h is an
invalid value. This is a fixed value.
29:10
Byte[20] Reserved
31:30
Word
Queue Size
Number of entry locations in history queue.
This value is 128.
33:32
Word
Queue Index
Last updated entry in queue. Queue Index is zero-based, so Queue
Index 0000h is the first location in the buffer (at offset 34). The most
recent temperature entered in the buffer is at Queue Index + 34.
See Note 1 and Note 2.
Table 71 Data Format of HDA Absolute Temperature History Table -1
Byte
Size
Field Name
Description
(Queue
Size+33):34
Byte[Queue Size]
Queue Buffer This is a circular buffer of absolute HDA
Temperature values. These are one byte 2’s
complement numbers, which allow a range from
-127°C to +127°C to be specified. A value of 80h
indicates an initial value or a discontinuity in
temperature recording.
The Actual time between samples may vary
because commands may not be interrupted. The
sampling period is the minimum time between
samples. See Note 1.
If the host changes the logging interval using the
volatile option, the interval between entries in the
queue may change between power cycles with no
indication to the host.
511
(Queue Size +34)
Byte
[512-Queue Size-34]
Reserved
