microcontroller
According to the research I have done so far it appears that the stability of the internal clock of a typical microcontroller is approximately 1% (calibrated) to 10% (uncalibrated). Do you agree with these numbers? Which microcontroller has the most stable internal clock?
Thank you!
It is rare to have that kind of failure. You might expect to see a little more noise on a pin, or have that pin completely non-functional. But to have it "somewhat work, but not in a useful way" is rare. I would suspect there are design issues that are causing the problems, and have something to do with a difference between the 164A and 164P. Since jitter is high, I would look at power related things. Are all the power/gnd pins connected? Are are the I/O pins either driven or pulled high or low? Etc.
But there still remains the possibility that the parts are bad. It's rare, but not unheard of. The only real way to tell is to get some more parts, from a different supplier, and try them. If they work, then you need to investigate further and see if you killed them in handling/soldering or if they really did come from Digikey bad.
If you are willing to do the measurement over a period of time (one midnight to the next), the frequency of the US power grid is maintained to exactly 60 Hz over a 24-hour period as discussed here. The frequency will vary during the day, but it is trimmed at the end of the day so that exactly 5,184,000 (60*60*60*24) cycles will occur from one midnight to the next.
To count this, you will need a zero-crossing detector. There are many such circuits on the web, here's a fairly simple one:
Count up how many cycles your clock is putting out in 24 hours (perhaps after going through a divider), and then compare those counts with the counts off the power lines.
Run this the first time and it will give you the frequency. Run it another day and it will give you the drift.
Best Answer
Based on your comment that you want 1ms error maximum in 4 seconds, I would say that no microcontroller has an internal RC clock that is that accurate under typical operating conditions. +/-0.025%.
It's also probably too tight for a ceramic resonator (more like 0.1 to 0.5%).
On the other hand, it's well within expectations for a typical inexpensive crystal, but if you want to be really sure you can use an external oscillator, which will be guaranteed over temperature and for initial accuracy.