Thanks,
   I was about to blame these guys who sold me chips.
 Really, I don't use CCP and other extra stuff, rather simple
 code is within one bank.
   After your post, I begun to suspect things are not so
 simple. So I wrote a small program to toggle Port B 0 pin.
 It started normally, I checked it with the scope. So oscillator
 matters are out of the game as well as MCLR etc, I think.
   I'll look through the program these days.(PICing is my
hobby).

   Thanks again.
   Mike.



Olin Lathrop wrote:
> All these are long shots, but here goes in random mind-blurt order:
>
> 1  -  Get rid of the code that disables the comparator since the 871
> doesn't have a comparator.
>
> 2  -  Make really really sure your code isn't trying to use CCP2 since
the
> 871 doesn't have that either.
>
> 3  -  Check for a bug in your code that might have been covered up by
the
> dead instructions in the extra unused memory space of the 874.
>
> 4  -  You should rebuild the code specifically for the 871.  That
would
> guarantee to catch problems 1 and 2 above.  It would also make sure
the
> linker didn't decide to stick something into the high addresses of the
> 874.
>
> 5  -  You didn't say what speed crystal you were using, but maybe the
> oscillator configuration is marginal and the 874s happened to work but
> that batch of 871s aren't as tolerant.
>
> 6  -  Look at the oscillator on a scope during these 4 - 6 seconds.
What
> is it doing?  Don't forget to switch the probe to high impedence.  Is
it
> an oscillator problem or a code problem?
>
> 7  -  Check what exactly MCLR is doing during the 4 - 6 seconds.
>
> Now that I've looked this list over, start with #4, which allows you
to
> immediately check off #1 and #2.  Then do #6 and #7 next.  You need to
> know what the oscillator and MCLR are doing before chasing after
anything
> else.
>

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