Goran,

I agree with Steve, use an off-the-shelf oscillator. Crystal oscillators on the microcontroller are subject to changes in board material, layout, and IC layout. Many problems have been created by changing the board layout or when the manufacurer of the IC does a die shrink. It may cost a little more to use an oscillator, but you can sleep better at night.

If the microcontrollers are very far apart, use two oscillators to reduce EMI.

Cory Spackman