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Subject: Re: Problems with cristal as clock for atmel AT90S8535
Date: Thu, 7 Nov 2002 00:43:50 +0100
Organization: University of Twente, Enschede, The Netherlands
NNTP-Posting-Date: 6 Nov 2002 23:43:46 GMT
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"Dave VanHorn" wrote in message
> > At the moment i have a 8 Mhz cristal connected to X1 and X2 and two 22pF
> > capacitors here a little ascii art to make it more clear:
> You probably need to double up the cap sizes. The caps are in series,
> the point of view of the crystal.
serie? are they not paralel
= = (capacitors)
> > -----| 22pF
> > X2 |-------|-------][---|
> > | cristal 8Mhz |
> > X1 |-------|-------][---|
> > -----| 22pF |
> > GND
> Does the ground lead go directly, and only, to one of the 8535 ground
yes ,the same ground that is connected to the ground of the atmel (pin 11)
> > I used a hosonic 8Mhz b214 in a HC-49/U case.
> > (it's a cristal in a metal case with two pins)
> > I can not find any datasheet of it.
> Not good, but it should still run.
which cristal should i use?
an oscilator with 4 pins (5 V,ground, output ) ?
and connect that one to X1 ?
> > I tried to measure the cristal via a osciloscope.. but i think the
> > to weak to measure.
> > many schematics i see on internet i see have this construction.
> Probe the xtal out pin only.
with a other cristal oscilator?
but then a DIL version:
i use now someting like this:
> > so i assume the atmel has an amplifier build in for the cristal.
> > I thougt the two small capacitors were there to make teh cristal
> > out of it self and it did not need any extra signal to make a signal.
> They are providing the load capacitance that the crystal needs.
> > How does a cristal actualy work.. does it just make a sinus wave all the
> > time out of itself?
> Nope, but at 8 MHz, the phase shift through the crystal, with the right
> in place, will be 180 degrees.
so i do not need to have any voltage input for the kristal?
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