AVR-Chat

Thanks for your reply.

I am planing to use a 16Mhz crystal with an
atmega128 mcu. I saw some schematic use
some values, and some do not use cap at all.

I saw some crystal spec mentioning about
load cap. Does this value come into the
formulate somehow? What if I do not use 
cap? What will happen?

I am pretty new to electronics. So when you
mention about parallel operation. What
do you mean? Outputing data to a port
for example?

thank you again

--- In AVR-Chat@yahoogroups.com, David VanHorn <dvanhorn@c...> wrote:

> 
> There used to be a page on this.. Back when I had web hosting :)
> 
> Use a crystal specified for parallel operation. It will have a
loading cap spec.
> 
> Take the crystal's specified load capacitance.  (22pF typical)
> Double it (44pF)
> Subtract 5pF for the parasitics in the circuit (39pF)
> 
> Use two 39pF caps in this case. 
> Without measuring the parasitics, or a shortwave receiver to get the
crystal's exact frequency, this will get you pretty close.