At 01:19 PM 2/22/00 -0800, you wrote:
>How about adding the diodes as shown in the data book??
>We've been using the pullup (47K), diode, and .01 to .1uF cap for a couple
>of years.
>Any other experiences with this combination?
>Kelly

I've been doing this (R and C on MCLR) and I haven't seen any damage to the
parts.  I'm planning on adding the diode on the next spin of the board,
because for me to reprogram these suckers with my boot loader I have to
wait like 10 minutes for the cap to drain (unless I grab it with tweezers).
 The tweezer approach won't work when the boards are conformal coated!  BTW
I'm using 16F876 parts.

HTH


>
>
>
>At 12:45 PM 2/22/00 -0700, you wrote:
>>At 04:19 AM 2/23/00 +1100, you wrote:
>>>Dan Michaels wrote:
>>>
>>>> Secondly, I've found, much to my chagrin (meaning $$$ wasted),
>>>> that you don't want to tie a capacitor straight onto MCLR on a PIC,
>>>> as this can damage the chip and lead to very large leakage
>>>> currents into the MCLR line (order of 100s of uA).
>>>
>>>  What I think you mean is that a large cap on MCLR pulls it well above
>>>Vcc when Vcc is shut off and that may cause strange behaviour.
>>>--
>>>  Cheers,
>>>        Paul B.
>>>
>>
>>Paul,
>>
>>Right. My take on it is, when you shutdown the system, Vcc goes
>>down fast and the cap discharges into MCLR, damaging internal
>>circuitry, probably the programming (rather than reset) stuff.
>>
>>The chips are clearly damaged, as evidenced by large *quiescent*
>>leakage currents into MCLR, subsequently (cap or no cap). How/why
>>this causes flaky/hit-or-miss program execution, I have no idea.
>>
>>Because of this susceptibility, I now use lower pullup R's (1-5K,
>>formerly used 20-50K), and NEVER tie any caps on MCLR.
>>
>>- Dan Michaels
>>Oricom Technologies
>>http://www.sni.net/~oricom
>>==================
>>
>>
>William K. Borsum, P.E. -- OEM Dataloggers and Instrumentation Systems
><borsum@dascor.com> & <www.dascor.com>San Diego, California, USA

Erik Reikes
Software Engineer
Xsilogy, Inc.

ereikes@xsilogy.com
ph : (858) 535-5113
fax : (858) 535-5163
cell : (858) 663-1206