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Fuser Dist Small.zip

Fuser Dist Small.zip

2006-01-21 by Dave VanHorn

I just uploaded a little hack that might prove useful to others.

This is a tiny-11 project, that programs the fuse bits of a M128.

Why?

Well, the default state of the CKOPT fuse in the M128 and others 
enables a low power "vittoz" oscillator, (google it) which can cause 
you some real problems if you're not designing for it.  BTW: to date 
I've seen no design guidance from atmel on using this mode. 

In this Vittoz mode, the crystal runs from 0V to about 1/2VCC instead 
of rail to rail.  This saves power, but if the crystal amplitude is 
just a little low, very odd things may start to happen.  Wierd, 
slightly wrong serial baud rates, non-deterministic execution, un-
reproducable bugs, or if you're very lucky, it will just not run.

If you're supremely unlucky, you'll have shipped a bunch of these 
with CKOPT in the default "Unprogrammed" or 1 state, and you'll only 
notice problems later when VCC or temperature changes, you get a 
different crystal vendor/batch, or you get AVR chips with a different 
date code that don't drive quite as hard.

So in case someone finds themselves in that position, here's a quick 
hack that just needs a programmed tiny-11, a 10 or 6 pin header, and 
a resistor.  Plug it in, and when the target starts running again, 
it's done.

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