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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.
Reserved
511
(Queue Size +34)
Byte
[512-Queue Size-34]
Note 1 – The Absolute HDA Temperature History is preserved across power cycles with the requirement that
when the drive powers up, a new entry is made in the history queue of 80h, an invalid absolute temperature
value. This way an application viewing the history can see the discontinuity in temperature result from the drive
being turned off.
Note 2 – When the Absolute HDA Temperature history is cleared, for new drives or after changing the Logging
Interval, the Queue Index shall be set to zero and the first queue location shall be set to the current Absolute
HDA Temperature value. All remaining queue locations are set to 80h.
Table 72 Data Format of HDA Absolute Temperature History Table -2
107
Western Digital Ultrastar DC HC310 SATA Product Manual