
Normally, I would include the Tiny-11 and M128 data sheets in this ZIP, 
but by not including them, it shrinks the dist from 3164k to 6k.
You can DL the data sheets if you need them.

WHAT THIS IS:

A quick hack to program fuse bits on a mega-128 system that got 
shipped with the CKOPT fuse in the wrong state.

It's also a little mini-tutorial on serial programming of the AVR, and
could be worked into a "code loader" using a chip large enough to hold 
the target code in rom. 

THE PROBLEM:

The default for the CKOPT fuse is "Unprogrammed" or 1, and this enables a low
power "Vittoz mode" oscillator. (google it.)

IF you are not prepared for it, this low power mode is no end of trouble 
and wierd non-deterministic behaviour.

IF you're lucky, your prototypes will crash and behave badly, but if you're
not, they will work fine and this will only surface after you've shipped a 
bunch of systems. Then the temperature shifts enough that some stages in the
chip don't clock always, like maybe the UART baud rate generator, or timers,
or you get other snaky hard to find problems.

The low power mode can be used, but only if you exercise far more care in 
crystal selection than is usually done.  

To date, I have not seen any app notes or data from Atmel on how to select
a crystal for this mode. 

Do you think that I'm exaggerating, and the problem can't really be this bad?
Good luck.
