Simple clock question

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Hi there,

There is something that I can't find in any Atmel's document. If I have connected an 8MHz external crystal (22pF capacitors), which is the best fuse bits sellection: Ext.Crystal 3.0-8.0MHz or 8.0- MHz???

Thanks for your time,

Michael.

Michael.

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1st option 8mhz xtal. 2nd option for 16 or 20 mhz xtal.

Imagecraft compiler user

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Both are equally good. There is a fair amount of overlap so there should not be any problem.

My guess is that the lower range will consume less power, so that would be the way to go if your design is power consumption sensitive.

If you think education is expensive, try ignorance.

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Quote:
Both are equally good. There is a fair amount of overlap so there should not be any problem.

I was thinking the same thing, but is there any data sheet or APnote from ATMEL???

Michael.

Michael.

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There is an App note that discusses drive level, crystal cut mode etc. You will have to weigh up for yourself any power advantages.

Otherwise you have a glass half-empty / half-full situation. You still possess the same amount of water, it will still quench the same amount of thirst. But which description satisfies your pessimism / optimism.

David.

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I would try the first option, THEN the second if the crystal fails to oscillate. The reason being is that the higher frequency crystals - depending on construction may need the stronger drive to get them out of bed. :P

Jim

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