Quote Originally Posted by buntay View Post
The only question I have is how stable is the clock speeds of a 20X2?
Whenever I've used a PICAXE with an internal oscillator its timing has been bang-on when I've looked at hardware output with a logic analyser.

I would say it's probably going to be 'good enough' and, if worried it might not be, just choose a 28X2 instead and use an external resonator.

It can be false economy to try and minimise costs when something is just a small part of a project and the savings pretty minimal.

Though I'm not entirely sure that PICAXE clock accuracy matters much. I would have expected you to be using a battery backed-up RTC for timing so you can handle loss of power and missed time easily.