Re: questions about crystals
"series" or "parallel" from the crystal standpoint, is only a frequency calibration issue. 99.99% of the crystal oscillators integrated onto micro. is of the Pierce configuration which will have a load that appears in series with the crystal to form the final frequency. the load is usually on the order of 10pF to 30pF. the effect of this load is threefold (at least) it affects the oscillator frequency(smaller load capacitance means higher frequency), Gain margin (higher the load capacitance the lower the margin), crystal power dissapation (higher the load capacitance the higher the crystal power dissapation will be). Generally for microcontroller applications(or similar) a very lite load(small caps) is desirable since frequency stabiality is not real important and reliable operation is. hope this helps