Excellent, thanks to all who helped clear this up for me!

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of promero
> Sent: Friday, April 27, 2001 12:09 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: tmr0 on 16F84 interrupt period
>
>
>
>
> Nick Veys wrote:
>
> > Ok, so I have the clock coming in @ 4MHz, effectively 1MHz to
> the processor.
> > If I set the prescalar to 1 and assign it to the WDT I'll get a 1:1
> > prescalar and an interrupt every ~244us.
>
> if you are using TMR0 as a free running timer (without
> prescaler), then it will
> set its interrupt flag every 256 us
>
> > Now I know that I can add to that
> > value to speed it up so that's good, but my one problem with this is, I
> > don't want to use the Watchdog timer... If I have it disabled but still
> > assign the prescalar to the watchdog, will it be disabled?  The /only/
> > interrupt I want is the tmr0 one.
> >
>
> As long as you keep the watchdog timer disabled, you will never
> get a WDT reset.
>
> >
> > > >Just double checking this.  At 4MHz, the timer will interrupt every:
> > > >256((2^(prescaler+1)/(2^22)) seconds.  So with a 0 prescalar
> you'll be
> > > >getting an interrupt every: 256(2/(2^22)) seconds (122us)?  This
> > > appears to
> > > >be the smallest obtainable period with this clock speed.  If
> anyone can
> > > >confirm this, it'd be much appreciated!!
> > >
> > > No, actually at 4MHz, TMR0 will interrupt every 256us with a 1:1
> > > prescaler.
>
> > >
> > > >sheet, I'd appreciate that too.  The datasheet merely says
> 1:2 .. 1:256
> > > >prescalars are available and I only assume that means
> > > clock/2^(prescale+1).
> > >
> > > The datasheet says that the minimum prescale value for TMR0
> is 1:2 when
> > > assigned to TMR0.  To achieve a 1:1 scale for TMR0, assign the
> > > prescaler to
> > > the WDT instead of TMR0.
> > >
> > > --Andrew
> >
> > --
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