> I have setup an external interrupt on RB0 of
> P16F877-20P. On the rising edge, the controller
> entered the interrupt service routine, but exited the
> routine automatically after half a sencond without any
> changes of the external condition.

You need to explain this better.  What do you mean by "exited the routine
automatically" after half a second.  Automatically as opposed to what?  What
do you mean by "exited"?  Deliberately returned via RETFIE or just jumped
somewhere unexpected?  Unless you are using interrupts in an unusual way,
you probably want the interrupt routine to return as soon as possible.
500mS is a VERY long time for a normal interrupt.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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