16F887 20Mhz External Clock Problems

[BrianT]

I have had very intermittent results with 20 Mhz 3 leg resonators. 4 MHz resonators work every time on every chip I have tried but 20 MHz units have been most disappointing. A few work, most don't. I have tried HS and XT settings but the answer is always the same - intermittent working and bulk frustration.

Go for the appropriate cut crystal, preferably with the recommended capacitors and I reckon your clock problems will vanish. I have just soldered the crystal into the outer pin positions of the resonator PCB footprint and left the capacitors off and over the last 5 years or more have never had a unit run significantly off frequency.

HTH
BrianT