Constantin:
I have a dumb question... is there such a thing as polarity with crystals or resonators? I thought they weren't polar, i.e. any orientation is OK.The reason I ask is that I have a Atmega 1284P here which is operating at maybe 10% of nameplate speed. The crystal is allegedly a 16MHz version, though I am beginning to doubt it. Maybe my supplier sent me a 1.6MHz version instead?
If that's the problem, how would one determine the speed of a crystal other than breadboarding it with a Atmega and watching different "blink" sketch responses?
FWIW, the backside of the crystal states "TXC G" and "16.0Dk7F"
Here's one way I found, using a counter and a "dip" meter:
Neither are common bench test devices (unless you work with RF or other oscillating circuits with regularity; pun kinda intended).
Here's a thread, in which a similar method is described:
http://forums.qrz.com/showthread.php?188949-unknown-crystal-how-do-you-find-frequency
There's probably a way of doing the above using a high-speed oscillator circuit (or a frequency generator?) and an oscilloscope to look for resonance (which is, IIRC, what the dip meter and counter method are doing).