By setting the OPTION_REG bit 3 I put the prescaler to the WD. I need a 1:1
TIMER 0 in my application. So the bit PSA (OPTION_REG bit 3) has to be set.
But by setting it the prescaler goes to the WD. My problem is that it
generates a reset a short time after because of the WDT which should be
disabled.
So how can i get safely a timer 0 without prescaler and without an undesired
WDT-reset?



-----Message d'origine-----
De : pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]De la part de Dale Botkin
Envoye : mercredi 28 aout 2002 16:18
A : PICLIST@MITVMA.MIT.EDU
Objet : Re: [PIC]:problem with Watch-Dog


On Wed, 28 Aug 2002, Samuel BOUQUET wrote:

> Here is the #fuses line:
>         #fuses XT, NOPROTECT, NOWDT, PUT, NOPROTECT, NOBROWNOUT, NOLVP,
WRT, CPD

That's correct, and will disable WDT.

> I read on a Microchip datasheet (Mid Range Reference Manuel, 33023.pdf)
that
> there are assemblary lines to get the PIC working on a good way (page
176).I
> am working on it to try to get the timer working good. the WDT seems to be
> stop with those instructions.

That procedure is needed when switching the prescaler between the WDT and
TIMER0, whether you have the WDT enabled or not.  I think the problem is
occurring when you manually set OPTION_REG bit 3.  What are you trying to
accomplish with that?  This line:

setup_counters (RTCC_EXT_H_TO_L, RTCC_DIV_2);

will (safely) assign the prescaler to TIMER0, you don't need to do it
yourself.  The compiler will use the corerct procedure to avoid the
problem noted in the midrange manual.  Just delete the "bit_set
(OPTION_REG, 3)" statement and I think you'll be OK.

Dale

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