Sounds like MCLR is floating.

On Sat, 16 Nov 2002 13:38:32 +0300, you wrote:

>   I need your advices, guys.
>
>   I have few working 16F874-based boards.
>   I decided to replace 16F874 by cheaper 16F871
> as code is about 1K locations.
> Ordered and received a couple of PIC16F871-I/P
> $3.6 each from local Microchip folks.
>   Placed them on the boards, programmed with the
> same code and the same configuration word, verified.
>
>   Now all is working fine, but-t-t start - up time got
> unacceptable: first 16F871 - 4.4 s, second - 6.3 s.
>  The same code working with I/O ports and RS-232
> through ICL-232, the same config word "3FFE",
> the same boards and  crystals, only PICs are changed
> and all these resulted in different damned start - up
> times 4 - 6 seconds. (The time between Power-Up
> moment and when PIC starts to send repeatedly
> bytes (250 bytes per second) to PC. I monitor it with
> a scope.)
>
>   With 16F874 on board start - up time is almost
> imperceptible.
>   I tried different crystals and resistors with them:
> the picture is the same.
>
> What am I missing?
> Maybe something simple & obvious?
> I need your advices, guys.
>
> Thank you.
>  Mike.
>
>PS: Locations:
>h2007 - config word (h3FFE)
>h2006 - device ID value (h0D21)
>h2005 - (h3F15) - what is it? Does anybody know?
>h2004 - (0000)
>h2000-h2003 - (h3FFF)

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