> "E" ("bad") revision wasn't used until late 2004.
My understanding of the current DS1620 data sheet is that you can better than
0.5 C resolution, by reading some extra registers and doing a subtraction and a
division, as mentioned below. Just wondering if this is something that could be
accessible in a recent Thunderbolt, or is the firmware not modifiable, and the
chip's 3-wire interface is not available externally?
http://datasheets.maxim-ic.com/en/ds/DS1620.pdf
Higher resolutions may be obtained by reading the temperature, and truncating
the 0.5°C bit (the LSB)
from the read value. This value is TEMP_READ. The value left in the counter may
then be read by
issuing a READ COUNTER command. This value is the count remaining
(COUNT_REMAIN) after the
gate period has ceased. By loading the value of the slope accumulator into the
count register (using the
READ SLOPE command), this value may then be read, yielding the number of counts
per degree C
(COUNT_PER_C) at that temperature. The actual temperature may be then be
calculated by the user
using the following:
TEMPERATURE=TEMP_READ-0.25 + ((COUNT_PER_C - COUNT_REMAIN)/COUNT_PER_C)
John Beale
(list lurker - first post)
N8JUF
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