piclist 2001\01\19\083507a >
Thread: Reading Outputs as Inputs
www.piclist.com/techref/microchip/ios.htm?key=input
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face BY : mikespamBeGone@@spam@whitewing.co.uk



On Fri, 19 Jan 2001 19:54:39 +1100, you wrote:

>Bob Ammerman wrote:
>>
>> > Barry,
>> >
>> > I am trying to avoing the adding of a pull-up.  Till now, the pin had no
>> > purpose.  It is not connected to any circuitry except for a header.  Now I
>> > want to use that pin as an input to allow the user to select a setting (by
>> > shorting or not shorting the header to power or ground.
<snip>
{Quote hidden}

When you've seen a JW pic with bond wires GLOWING and it still works
afterwards you have a lot of faith in the PICs robustness.
>Doing it only for "an instruction or two" doesn't
>seem to make it any better, it is still so far
>out of spec to be scary. It does make a big difference - the only damage mechanism is thermal
heating. If you limit it to a few microseconds there isn't much chance
of heating even something as small as an on-chip transistor enough to
burn it. Also, a short pulse will be supplied by the decoupling cap, so you
don;t risk causing a brownout.

>I would much prefer to
>overclock a PIC at 1.5x its clock freqency than to
>do something like this!
I would disagree - overclockability will be more dependent on
part-to-part differences than the heating effect of a few
microseconds' output short. I would still only use it for 'very occasional' use - things like
production test though.

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