> Don't confuse common practise with good idea.  I can live 
> with 10nF as upper limit although I doubt there is a 
> legitimate reason for going above 1nF. However 100nF is 
> definitely excessive is you are intending the circuit to work 
> with ICSP.  Again, do you really want a 1.3A pulse during programming?

And the solution is simple. You can have your cap for a power-on reset,
but keep some resistance between the cap and the MCLR. How much is a
balance between drive capalility of your progger and the amount of such
current that is tolerable, and the track distance and junk field
strength. Keep it short, and use 1 k (with Olins proggers?) .. 33k (with
Wisp628, which has a more feeble MCLR drive, maybe even higher when you
misuse a PS+ as ICSP progger) and you will be fine in all but the most
exception situations. And you can have a big cap (10s of uF's) without
destroying the PIC.


Wouter van Ooijen

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Van Ooijen Technische Informatica: www.voti.nl
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docent Hogeschool van Utrecht: www.voti.nl/hvu
 
 

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