At 12:49 PM 2/7/00 +0100, Thomas wrote: >I'm just wondering if the capacity of the two capacitors in the crystal >oscilator is important. i have two 22pF for my 4 Mhz crystal. Some projekts >use different values. Does that make a difference? 1. Sometimes the oscillator won't work if you don't have enough capacitance, although > 15 pF and < 100 pF should work at 4 MHz. 2. The size of the capacitors used will increase with increasing frequency. 3. About 27-33 pF seems to work best (i.e., give closest to exact frequency) for 4 MHz. About 22 pF works for 8 MHz. About 15-22 pF for 20 MHz. 4. You can pull the crystal frequency about +/- 0.01% by adjusting the capacitors used, particularly the OSC1 capacitor. You would do this to get the exact frequency 4.00000 MHz. ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral@lcfltd.com Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causae scire" ================================================================