Thanks for answering, but,

<peiserma <at> ridgid.com> writes:
> The specs you listed come from Absolute Maximum ratings. The datasheet very 
> clearly says this is a stress
> rating only and functional operation is not implied. The absolute max ratings 
> only list the guaranteed
> limits under which the device will not emit the magic smoke.
> 
> Note there is still some debate wrt to the input protection diodes. I never
use > them intentionally, since
> doing so implies i'm violating the input voltage specs. The spec is Vss-0.6V. 
> You say you put -8.2V on an
> input. Thats clearly out of spec. The only reason you might be measuring -0.6V 
> is because the diodes are
> already conducting...

No, I put -8.2V *through* 1k on the pin. Even so, I don't think that it's
reasonable for the limit to be so stringent that a Schottky clamp must be used.
What's the use of a $0.5 MCU if it needs $1 in Schottky clamps to make 8 IO pins
that can be connected to usual external wires without freezing the chip. As you
know, external wiring will conduct glitches etc and these should be clamped by
the diodes. Yet in this chip they also freeze it. I am not sure if the WDT is
also frozen, I have not tested it enough.

By the way putting in an old 16F84 for testing works fine without clamps of any
kind (as expected).

thanks,
Peter P.


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