On 05-Feb-02 wouter van ooijen & floortje hanneman wrote:
>> I can't see now a simple switch to ground and a 10K pull up to Vcc and a
> small
>> capacitor are going to create voltage spikes below ground that can pump
>> 80mA of current into the MCLR pin.  Even with a several inches of wire to
> the
>> switch I doubt there would be enough inductance about to cause problems.
>
> The cap can!

Wouter,

Please explain in more detail how you think this can happen.

Do you mean that the capacitor (acting as a capacitor) can create the negative
voltage, OR that the capacitor (acting as an inductor) can create the negative
voltage.
>
>> Is the MCLR input any different in this respect to other pins ?
>
> Yes, it does not have the normal protection diode to Vcc (because it must
> accept the ~14 V Vpp). I guess RA4 is similar.

OK, but we are talking about problems caused by negative spikes going below Vss
not posititive spikes going above Vcc.

Peter

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads