Clock Jitter

I got my new Tiny45s this week and programmed up one yesterday. It worked but it didn't look so good. After further analysis I have determined that although the Tiny45 has a much more versatile internal clock, it is a much less stable one. Here is the observed clock stability looking at one each of the two parts:

	Tiny12		100 ppm
	Tiny45		3000 ppm

I measured this by watching edge jitter over 5 second intervals for edges that were from 2us to 20 ms apart. I made these measurements with my digital scope using 5-sec variable persistence and window-delay (old b-delay). I thought that the Tiny45 might be inserting wait-states non-deterministically in the ram accesses. The new part has a ram and keeps the return address stack in it. But I was able to rule this out by observing the internal clock directly using a new fuse option that routes the internal clock to an output pin.

I'm sitting here thinking that I should try a few more parts before I get too discouraged. I'll let you know if I discover part to part variation. But for now the conclusion is that the new part can't do one chip video. Bummer.


Last edited March 4, 2006
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