On Nov 10, 2005, at 11:38 PM, Vincent Trouilliez wrote:
I set my function generator to 1MHz to be safe. My
generator is a bit old and at that frequency the square wave looks
more
like a sine, but somehow the AVR is happy with it... who said digital
circuits were picky...
The crystal oscillator circuit is analog. The delta voltage the
crystal swings is pretty low. Way out of normal TTL or CMOS switching
ranges. You observed about 2 volts on the pins. If the crystal was
running it might have been only 50 mV AC on that 2V DC bias.
There is some magic to making crystals oscillate. Not all crystals
are alike. Motorola/Freescale is very good about spec'ing crystals,
Atmel is sloppy. Wrote to Atmel once asking and was told the page
number to consult in the manual for setting oscillator fuses. Wrong
answer. I wanted to know, "Series, parallel, A/T cut, drive level,
capacitance, etc?"
--
David Kelly N4HHE, [EMAIL PROTECTED]
========================================================================
Whom computers would destroy, they must first drive mad.
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