Hi,

> I've got this signal
>
> http://home.clear.net.nz/pages/joecolquitt/lv_an.html
>
> going into AN0 of a 16F877. It works but the signal must
> have some negative-going components (or possibly a
> switch glitch) as the port occassionally latches. How can
> I best protect the pin against signals going below Vss-0.6V


    I would put a resistor in series with the signal, a cap after the
resistor to ground and to be on the safe region use a schockty diode reverse
biased to ground. That should clear any problems you might be having
directly. Should be easy to test. The values will depend on the response you
need but basically 100 ohms and 10 nf should leave fast glitches out and
should not affect your circuit operation.

best regards,
Alexandre Guimaraes

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