ATMega48V - longer startup delay with external crystal

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Hi,

when using external crystal it should take only 14CK (+ optional WDT timeout) to "wake up" from reset. With ATMega48V I have tried different crystals (both clock crystal and a 8MHz one) and different reset times but it always count either 1K or 16K cycles that should be counted only after power-down. Why? Is the datasheet wrong?

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Last Edited: Thu. Oct 10, 2019 - 12:39 PM
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Smajdalf wrote:
when using external crystal it should take only 14CK

I'd like to start there.  14 clocks is about a microsecond.  IME it takes even a "warm" crystal on the order of a millisecond to become stable when awakening from power-down sleep, and thus I use a different clock source in apps that need a fast wakeup time.

 

So maybe you sparkies can shed some light on that?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Are you really using a '48V?  That must have a date code from over 10 years ago, right?

 

Anyway, I think you misread the table.  The 14CK is >>additional<< time coming out of reset, over the base number for starting the crystal.

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Thank you, I really misread the datasheet. Crystal is running while in reset so I expected it is considered stable when leaving reset.

48V is the cheapest on eBay. The date code is 1602 - you are right, it is old.