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.