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Author Topic: Resonator Vs Crystal Vs Internal Resonator  (Read 3889 times)
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Shannon Member
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Perhaps the datasheet is nonsense on this matter (I found it odd that the rating for fixed voltage fixed temperature was 10% whereas for unspecified temp/voltage was 1%...)  This suggests that the factory setting is actually +/- 1% (but only at 3V 25C).  Can't hurt to assume the worst and recalibrate under expected conditions.

Do worry about the temperature variation though...  All works fine till a hot day in summer!
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In the crystals.txt file in the git link below you will find some frequency measurements for crystals, resonators, and RC oscillators, including variations on OSCCAL.

  https://github.com/manitou48/crystals
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OSCAL is done at chip test before encapsulation and according to a basic measurement a close value is programmed as a default.  Has to be as no one would pot a chip and then test it and you can be certain they are tested to "Some" functionality... How far is based on statistical models and varies by part family and process width and material for the same part.

Bob
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