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What is the maximum frequency for the AT90S2343?

In the official specs, it says 10 MHz as absolute maximum, but then, on the next page in figure 39 (acive supply current vs. frequency) the graphs are drawn well beyond 50% over that rating (15 MHz). That same in figure 42...

Do I have to take special precautions, is the logic core unstable at these high frequencies, other side effects?

Regards,
Arms

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Read the speed on your chip

Jens

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Hi,

I don't know about 2343 since I haven't ever used it. I have a prototype on my desk at home and there is 8515 clocked at 10.24MHz. Eeprom and external ram is not used so I can't say anything about them, but all other things seems to be working allright. Supply voltage is 3.4V and the cpu is working so near to the maximum frequency that I'm planning to drop it back to 6.7MHz. I know it's
maximum frequency for 5V supply because I've tested the same chip a few months ago and it stopped working with higher frequencies than 11.592MHz.

2313-4 clocked at 18.432MHz but refused to be programmed. Both chips are dated around -98,
I don't know about newer versions.

Anyway, I don't think it's wise to use overclocked chip in commercial product. There are so many
environmental things that could cause erratic operation, temperature, for example. And changes in manufacturing (silicon) affects too.

So if your code isn't fast enough, the only "legal" solution would be optimizing your code.

Tommi

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Thanks for that info...

I'm running the 10 MHz rated 2343-P10 right now with 10,24 MHz. From your statements I figure, if i overclock the core temporarly in my tests, nothing gets broken... Worst thing is, that execution stops, right?

My code is fast enough right now, I'm just curious about these two odd figures in the Specs, with input current data up to 15 MHz (with the fastest 2343 rated at 10 MHz).

Low-Voltage programming is also no problem with the 10,24 MHz clock (in the manual, a maximum clock of 8 MHz was given during programming).

Arms

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Hi all!

We strongly urge you to operate your AVR devices within spec. We do not guarantee the correct operation outside of spec, and you're therefore on your own when something happens with your design.

Execution failure is not the only thing that can happen when you're running at too high frequencies. Your program counter may go juggernaut if your part is forced out of spec, and the program operation can become totally erratic. Usually, the first thing to go wrong is communication with the EEPROM, which is a slow interface.

Programming is even more critical, and there's no guarantee that the program you intended ends up in the part's memory if the programming interface is not clocked correctly.

The figures in the data sheet graphs you've observed do not mean the part can be operated under the depicted circumstances. All features are tested above and below spec, and the resulting operating spec is the interval of every parameter where we can guarantee the AVR's operation. We're considering truncating these graphs in order for this kind of misunderstanding not to happen.

Just say no! :)

Morten, AVR tech. support, Atmel FAE

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Hi Morten,

I'd just like to cast my vote for Atmel's continuing to publish the complete device characterization curves for parameters like current vs. clock freq.

I believe most engineers designing commercial products understand this information doesn't imply valid operation beyond the listed specs, and such data can be very useful.

Thanks lots!
-Mark

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