In addition to the lfuse settings described by Joerg, I suggest you have
a look at the CKOPT bit of hfuse: I read in the processor manual that
this bit should be programmed to 0 for clock speeds above 8 MHz.
Maybe some remarks from the "frog-perspective" can be of help - I am
just going through the starting-at-zero experience myself.
I decided out of pure defensiveness to invest in a JTAG - that should
allow working with a CPU whose clock has been lost and to rewrite its
fuse bytes to meaningful values (hfuse=0x99, lfuse=0xe1 for the on-chip
1MHz RC oscillator of an ATmega16). On the other hand, although I will
end up with an ATmeqa32, my initial experiences are made with an
ATmega16 - much less expensive to throw away by the dozen (so far
theory, touch wood ...).
I went very slowly initially: although I intended to go for a 14.474560
crystal, I stuck to the internal 1 MHz clock until (a) I felt at home
with using avrdude and (b) having read the relevent parts of the
processor manual sufficiently often to be safe when defining the fuse
bytes. For my high-speed crystal (crystal, not oscillator!), they are
0x09 (hi) and 0xe0 (lo).
And, have you had a look at the interactive mode of avrdude (-t option)?
very helpful when you want to know what is going on and just need to
know whether the CPU is still responding.
Good luck! Juergen
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