At 10:48 AM 3/27/01 -0500, Bob Ammerman wrote:
>The simplest solution, which many on the PICLIST will jump on immediately
>as being 'out of spec', is to just bring your signal into the PIC through
>a high value series resistor. This is depending on the input protection
>diodes of the PIC to clamp the signal and the resistor to limit the
>clamping current.

Did they ever publish a value for max current into a pin like that?

I don't have a problem with the approach, but I like to know where the
walls are.

Alternatively, use two resistors, and put in your own protection diodes to
VCC and ground, between them.  The outer resistor limits current from the
source, and your diodes can be pretty beefy. (anything's pretty beefy
compared to the on-chip diodes)  I'd guess 1k - 10k for the outer.

The second resistor limits current in case your diodes have a larger drop
than the on-chip diodes, and dosen't need to be too large a value. 1K
should be plenty.

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