This is what I was thinking too. My first thought was actually that the probe used to measure the signal might be killing the oscillator. If the feedback resistor is 1MOhm and you are loading it with a 100KOhm FET probe, then you pull the bias completely out of its linear region where the AC gain exists. So the oscillation stops.... The general advise is to probe the inverter output where this sensitivity for DC load does not exist. If you want to see the waveform on the input, add a capacitor in series with the probe tip to remove the DC load. Eddy > --- Andrew Ingraham <a.ingraham@xxxxxxxx> wrote: > > > > > 2) By keeping the load capacitance value > > same as 15pF, a 100K > > > externalresistor between the XTAL &EXTAL pin of > > the microcontroller, > > > population starts oscillations. > > > > I don't know much about xtal oscillators, but I'm > > wondering if there might > > be a DC bias problem with the circuit. With the > > circuit not oscillating, is > > the input (one of the pins) biased so that the > > inverters are in their linear > > (amplifying) region? Perhaps the 100K resistor is > > needed to help make that > > happen. > > > > Andy > > > > > ------------------------------------------------------------------ > > To unsubscribe from si-list: > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' > in > > the Subject field > > > > or to administer your membership from a web page, > go > > to: > > //www.freelists.org/webpage/si-list > > > > For help: > > si-list-request@xxxxxxxxxxxxx with 'help' in the > > Subject field > > > > > > List technical documents are available at: > > http://www.si-list.net > > > > List archives are viewable at: > > //www.freelists.org/archives/si-list > > or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > > Old (prior to June 6, 2001) list archives are > > viewable at: > > http://www.qsl.net/wb6tpu > > > > > > > > > > > ____________________________________________________________________________________Ready > for the edge of your seat? > Check out tonight's top picks on Yahoo! TV. > http://tv.yahoo.com/ > ____________________________________________________________________________________Be a better Globetrotter. Get better travel answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545469 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu