Lpc2000

At 12:04 AM 10/18/05 +0200, Sten wrote:
>lhaddix wrote:
> > I guess as Marcio points out the larger issue is why are there
> > situations where the internal watchdog can't reset the micro.
> > Unfortunately this is probably a feature of the LPC design.
> >
> > Microchip uses an internal RC for thier watchdog which is not
> > dependant of the system clock for instance.
> >
> > I think what happens is it's possible for an ESD hit to stop
> > the crystal osc on the LPC such that reset is needed to restart
> > the oscillator, but there can be no watchdog reset without a system
> > clock.
> >
> > I've considered using an external osc to feed the ARM, but don't
> > wish to do this. I can't be sure it would fix the problem without
> > mocking it up and then blasting with the static gun, but I know that
> > toggling reset from outside will restart the clock.
> >
> > Landrum
> >
>
>I had some similar problems with a LPC2124 last year. During ESD test
>the LPC stops with and without internal watchdog. But we had another
>(bigger) MCU on our board which was able to turn off/turn on the LPC if
>it didn't response to hello-request packet in such a case.


I think the additional micro as watchdog is not a bad idea.  A little 8 pin 
micro can act as quit a flexible watchdog.  1 pin for reset, 1 as the 
watchdog input, a couple to check for various startup or runtime 
conditions.  If it has a good reliable power monitor built in even 
better.  It' may even be cost competitive with a windowed watchdog.

Jack Ganselle has an article where he waxes rhapsodic about the possibilities.

Robert

" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/