All,

I worked yesterday getting my one wire routines working, which I accomplished.
The 1822 One Wire Temp Sensor is a 9 bit sensor.  It has a range of -55C to +125C.
It uses 2's complement math for the negative temps.  It's temperature measurement is
contained in 2 bytes.  The LSB is the temp reading in .5C increments.  The MSB is the
sign bit.  All 8 positions in the MSB are sign bits.  So, I gather that if the temp is negative, 
all 8 bits of the MSB would be set.   However, when the PIC reads the  Temp sensor, I get 
the correct (approximately) reading in the LSB, but the MSB has 1 or 2 bits set.  It's not 
clear to me from the datasheet whether all 8 bits should be set for negative temps, or if it can 
be any number of bits set for negative temps.

Does anyone have any experience with one wire comms, especially with this temp sensor?
If so, do you have any idea about the MSB and how the sign bit is supposed to work?
Or any other insight that may give me an idea if I'm doing anything wrong.

BTW, I've tried powering this sensor from Vdd and using parasite power, and it acts the same either way.
Also, I opowered it from 5 volts and from 3 volts, and that doesn't change anything either.

Please advise.


                                                                    Thanks and Regards,

                                                                               Jim
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