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Subject: Problems with cristal as clock for atmel AT90S8535
Date: Wed, 6 Nov 2002 23:03:08 +0100
Organization: University of Twente, Enschede, The Netherlands
NNTP-Posting-Date: 6 Nov 2002 22:03:03 GMT
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I'm building a simple ISP flash board for an atmel AT90S8535.
But i have some problems with the clock.
At the moment i have a 8 Mhz cristal connected to X1 and X2 and two 22pF
here a little ascii art to make it more clear:
| cristal 8Mhz |
-----| 22pF |
The problem is that i can not get any signal out of it.
But when i give a pulse via the parralellport or via a wave modulator
(between 1Mhz and 8Mhz) the board works fine.
I was wondering what i could do wrong here.
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.
I tried to measure the cristal via a osciloscope.. but i think the signal is
to weak to measure.
many schematics i see on internet i see have this construction.
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 osciliate
out of it self and it did not need any extra signal to make a signal.
How does a cristal actualy work.. does it just make a sinus wave all the
time out of itself?
or does it need any trigger?
Is there anyone here who might be able to help me with this problem?
Who made a simple flash board and could give me some advice?
Thanks in advanced
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