With all this discussion about RC oscillators, I just remembered a question
that I had some time ago, but forgot about since I just worked around my
question.

I want to generate a 4MHz clock speed with my 16F84 using an 18pF cap. (it's
all I have :)  How do I calculate this?  What I originally did was to make
the time constant = RC and take the inverse.  That gave me a value of ~13K
for the R.  My reasoning?  I have none, just doing this blindly, I'm not an
EE.  I do know that the time constant is the time the RC takes to discharge
to 33% of its peak, but that doesn't seem to work in my calculations either.

What turned out to give me ~2MHz was to use a 4.7K for the R with my 18pF
cap.  I wrote my code around this, but never really had a reason.

Now with this discussion about lowering the current draw, it might be
prudent to change my RC because I'm running my circuit off a battery.

This shouldn't be a tough one.  Thanks in advance.

--Drew
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