[avrdude-dev] [bug #35474] Feature request: print fuse values in safemode output.

[Joerg Wunsch]

Follow-up Comment #3, bug #35474 (project avrdude):

The issue with those "al cheapo" selfmade bitbang programmers
wasn't to overclock the ISP in terms of not satisfying the
f_ISP < f_CPU/4 requirement: you'll usually immediately
notice that, as it already fails to read out the signature
at start-up.

Their issue was that the drivers used (often just a simple
LS-TTL output), together with the length of the cables (you
somehow had to route the signals from your computer's printer
port to the desk) were prone to produce `flakey' signals,
which could eventually lead to the controller getting some
signal sequence that didn't really originate from the
programmer, due to signal distortion.  If you hit that really
bad, the sequence might have resulted in the clocking fuses
being modified, so upon leaving the ISP session, your
controller was at risk of being fused for a clock (like an
external crystal) that wasn't actually present, which resulted
in "shooting into your foot", as this disables further ISP
connections.

So the idea of the "safemode" implementation is to verify
the fuse setting just before closing the ISP session, to
give the user a chance of intervening.

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