>*All* crystals have both a series resonance mode and a parallel
>resonance mode, the circuit determines which one is used. If you see a
>load capacitance stated it means that the crystal will operate at the
>stated frequency in a parallel resonance oscillator circuit with that
>load capacitance. The resonant frequencies are quite close , and usually
>don't matter with microprocessor applications. Microprocessor oscillator
>circuits such as that employed in PICs use the crystal in parallel
>resonance mode.


I've seen so many complaints on various NGs and lists about crystals.
One mindset is that you can't possibly understand it, it's all voodoo, use
an oscillator.
Another is that it dosent' matter, just "hook it up" and fiddle with the
caps.

It's amazing that such a simple device gets such a bad reputation.

I have seen a lot of comments about not being able to get them on frequency,
and I suspect
it comes from using "junkbox" crystals, or buying the wrong type.