I'm using the PIC16F877 at 4MHz, XT osc.

I thought the same.  In the Mid-range manual, there is a very specific way
for the prescaler to be switched from TMR0 to the WDT, and vice versa.  It
is in Section 11.6.1.  I tried this, but it didn't seem to help.

BTW, there is an error in Microchip's manual, on page 11-8, example 11-1.
Line 6 should read :
BSF    STATUS, RP0
and not what is given.

-Mike


----- Original Message -----
From: "Josh Koffman" <listsjosh@3MTMP.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, August 07, 2002 4:21 PM
Subject: Re: [PIC]: TMR0 Mishaps (Sorry for double post)


> I don't know what PIC you are using, so I can't look up the data for
> myself, but maybe the problem has to do with your choice of oscillator.
> Perhaps there is a prescaler issue or something as well.
>
> Hopefully this might steer you in the general direction.
>
> Josh
>
> --
> A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.
>         -Douglas Adams
>
> "Michael A. Powers" wrote:
> > I wrote a program that interrupts on TMR0 overflows in the MPLAB
simulation,
> > but for some odd reason it doesn't work when programmed in a circuit.  I
> > have confirmed that the rest of the program and TMR0 are working, but
the
> > interrupt just doesn't fire when put into an actual circuit.  What could
be
> > the problem?
> >
> > (TMR0 source is CLKOUT)
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
>
>

--
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