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'[PIC]: - mailto:PICLIST@MITVMA.MIT.EDU?Subject=%5B'
2002\03\19@233014 by Bin Yu

picon face
"Interrupt on RB0 of P16F877"

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.

Only the external interrupt was enabled, and the
oscillator is runing at 11MHz.

My questions are
1. Did anyone else have the similar problem?
2. Did I set it up wrong?
3. How do I fix it?

Thanks,

YUB

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2002\03\20@005730 by michael brown

flavicon
face
> "Interrupt on RB0 of P16F877"
>
> 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.

Interrupt routines never exit "automatically".  What exactly do you mean?
If you executed a retfie instruction then the routine is finished and will
not be run again until another interrupt occurs.  Interrupts are not
"controlled" by external events, only triggered by them.  IOW, holding RB0
high will not force the interrupt routine to keep running over and over
(unless you forget to clear the INTF in which case it's not the RB0 pin that
is keeping the routine looping).

Sounds like maybe you have the watchdog timer enabled.

> Only the external interrupt was enabled, and the
> oscillator is runing at 11MHz.
>
> My questions are
> 1. Did anyone else have the similar problem?
> 2. Did I set it up wrong?

Did you read the datasheet? ;-)

> 3. How do I fix it?

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2002\03\20@010517 by Bob Blick

face picon face
Watchdog timer is enabled, resetting the processor?

On 19 Mar 2002 at 20:18, Bin Yu wrote:

{Quote hidden}

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2002\03\20@080225 by Olin Lathrop

face picon face
> 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, spam_OUTolinTakeThisOuTspamembedinc.com, http://www.embedinc.com

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