James, Try changing your configuration to HS mode. The only different is the higher amplitude. Use 2 scope probes connect them to both crystal pins at the same time and take a picture of it and let us see it. I use pic all the time I never had oscillation startup problem at all. Are you using water Soluble solder? Andre -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of James Cizek Sent: Friday, September 26, 2008 11:06 AM To: piclist@mit.edu Subject: [PIC] Oscillator stability question Hi folks, new to list but have been searching archives for several days now. I have been using 16F84 pics for a long time. No trouble. Venturing out to the 16F877A chip now and having LOTS of OSC problems. I found several people on list in the archives that seem to say the Murata ZTT-4.00MG ceramic osc works great. I cannot get mine to start at all. I gave up and went to a parallel cut 4.00mhz crystal with 27pf caps to ground. All leads are VERY short, and grounding is good. It will start, but oscillates wildly, one interesting point, if I touch the crystal pins while it's running (with my finger) it seems to settle down and operate close to proper. I get same results with breadboard OR soldered into circuits. I have tried several different 877's also with same result. I did see that in the datasheet for the 877 they show a resistor marked "RF" in series with the crystal and state that it "may be needed with AT strip cut crystals". Might I need this resistor? I am not sure if my crystals are strip AT, I was sold them as "parallel cut" and nothing more. Anyone have any insight on my instability with the 877?? Many thanks. -James -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist IMPORTANT NOTICE: This notice constitutes Proprietary Rights identification of this email including all attachments, which is property that is intended only for the use of the individual or entity to which it is addressed. It also may contain proprietary data or information that is privileged, confidential, or otherwise protected from disclosure under applicable law. The recipient of this data agrees to abide by the United States Export Control of Technical Data and Equipment under the International Traffic in Arms Regulations (ITAR) and Export Administration Regulations (EAR). The recipient agrees to abide by these laws and their regulations not only for export and re-export, but for disclosure to non-U.S. citizens. This email does not grant or assign rights of ownership in the proprietary subject matter herein, nor shall it be construed as a joint venture, partnership, teaming agreement, or other formal business relationship. If the reader of this e-mail transmission! is not the intended recipient or the employee or agent responsible for delivering the transmission to the intended recipient, you are hereby notified that any dissemination, distribution, copying or use of this e-mail or its contents is strictly prohibited. Please notify the sender you received it in error by responding to the e-mail and then permanently delete it and all copies of the e-mail immediately, including any copies of it in your deleted email folder. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist