Lpc2000

Tom Walsh wrote:

>
> I've been following this thread with interest as I expected to use the
> watchdog in my application.  The old design used a MAX690 where you
> would toggle the input to keep the watchdog happy.  This worked well for
> us as the foreground software would set the pin high and the interrupt
> routines would reset it low.  This ensured that both sections of the
> program were operating okay.  Foreground did non-time-critical tasks
> while the background serviced realtime critical tasks & communications
> over RS485.
>
> I had expected to do something similar with the LPC2000 parts.  Feed the
> watchdog with 0xaa from the interrupt layer and then feed it with 0x55
> from the foreground.  It was expected that even if the watchdog received
> something like this, it would still be fine:
>
> 0xaa, 0xaa, 0xaa, 0x55, 0xaa, 0xaa, 0xaa, 0xaa, 0x55 ....
>
>
> What value is a watchdog that requires you to carefully feed it, it
> sounds as if the watchdog is very fragile?  I noticed that Philips
> Applications people studiously stayed out of this thread about the
> watchdog!  I suspect that the watchdog is severly broken and they did
> not want to comment on it?
>
>
> Regards,
>
> TomW


At least I would say that its a bit strange behavior for a watchdog. 
Anyway there is a work around and it appears to work well (at least in 
my case). I have only noticed this on the LPC2138 part so I don't know 
if the same "problem" appears on other silicon. If it is that would have 
been nice to now though.

/Ake

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Ake Hedman (YAP - Yet Another Programmer)
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