Guys, When having problems with crystals, the thing you must check is the ESR rating of the crystal. I havnt followed the thread of this argument closely and cant remeber what speed your XTAl is, but in general, XTAL's are much harder to get going than Resonators. The equivalent series resistance is about 30 for XTALs at 5MHz and 150 for resonators at 5MHz. The choice of capacitors is dependant on this ESR value. See any XTAL manual s for more information, most give you the maths to work through if you have problems. regards, SW. ______________________________ Reply Separator _________________________________ Subject: Re: Osc. problems Author: pic microcontroller discussion list at INTERNET Date: 19/07/97 10:07 Andy Warren wrote:- >I have four suggestions, Tom: >1. Make sure that the Oscillator Type is set to HS (High Speed). >2. ONLY put the scope on Pin 15 (OSCOUT); unless you have a very high-impedance probe, putting it on Pin 16 (OSCIN) will load down the oscillator and can stop the clock. Note that the frequency on OSCOUT is OSCIN/4, so don't be surprised if you see "only" 5 MHz on that pin. I thought OSCOUT was OSCIN/4 only for RC not crystals. Also probing OSCOUT can stop the clock or alter the frequency, unless it is high impedance, low capacitance. >3. Check Vdd and Vss, and make sure the oscillator caps are tied to Vss, not Vdd. Does connecting osc caps to vdd affect the clock? (as long as the supply is decoupled well, I've not *yet* had a problem) >4. With the crystal, try using smaller caps (15 pF instead of 33 pF). With the ceramic resonator with built-in caps, make sure that those internal caps are in the 10 pF range. Yep, 15 or 18pf, not 33pf Hope this helps... -Andy === Andrew Warren - fastfwd@ix.netcom.com === Fast Forward Engineering, Vista, California === http://www.geocities.com/SiliconValley/2499