Tom=E1s =D3 h=C9ilidhe wrote:
> =

> James Nick Sears wrote:
>> And Olin, have YOU even looked at the datasheet?  There is some info
>> yes, but it's not immediately apparent how to select RC values or the
>> range of appropriate frequencies with an RC to someone who doesn't
>> have some prior knowledge of how RC oscillators work.
> =

> I know about RC circuits, about the time constant, about exponential =

> decay and all that. What I don't know is how the RC values actually =

> yield a specific processor speed. I just need an equation, something like:
> =

>     Processor Speed =3D 7.56 * Time Constant
> =

> And then my next question would be what capacitor value I should use, =

> given that I can have a really small one with a really big resistance, =

> or a really big one with a really small resistance.
> =


Right. And you have got your answers. The most
common seems to be "Do not do that, unless you
have a realy, realy good reason".

And, from what I know, there isn't any real
answer to your question, RC-osc doesn't give
a particualy predictable oscillator speed.

 > Could you give me a part number for one of these
 > resonator thingies?

Check :
http://www.voti.nl/shop/catalog.html?xtals
for a couple of examples.

Also note the application notes listed on the
oscillator page (page 64) in the data sheet.

 > I want something small and cheap.

What is "small" and what is "cheap" ?
And what about "works" ? :-)

Best Regards,
Jan-Erik.

-- =

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