I'm OK with how the WD is. You can't turn it off by
mistake, and if you
have a bug or bad data that your code didn't catch, things
get reset /
rebooted and life goes on. It's some work to get it all
going, but the
system just doesn't hang up or require manual re-boots. I
can't imagine an
embedded system without one.
I think I would have build the part with the reset state
such that the
watchdog was disabled so you could do time intensive stuff
like clear memory
or bootload, then turn it on with your once only write. But
there may be
other types of embedded stuff where on at boot is a win.
Things like the flash programmer (internal or external)
just need to kick
the WD as part of their main loop. I would think that a
boot loader could
kick it both while it waits for data and as it gets data.
Breaking a big
single loop into two loops and only kicking the watchdog on
the outer loop
minimize the time hit. Most code that would hang and wait
for something has
a fairly simple loop structure and it's not that hard to
kick it. I have it
set for the maximum amount of time.
A related trick: I have a hack that counts exceptions
(bad memory access,
writes to read only spaces, etc). A "global exception
counter" if it's
non-zero gets decremented once a second. If it ever gets to
100, I reboot.
So the occasional bug gets a chance to have its exception
reported via
syslog, but if things really go wrong there's a reboot.
Note that a number
of the offending exceptions still get reported via syslog,
so you can get a
clue as to what went wrong.
Between the two mechanisms, the platform has a lot of up
time and even
occasional or data/situation dependant errors can slowly be
tracked down
over a year or so.
- pete
> -----Original Message-----
> From: ColdFire lists.wildrice.com [mailto:ColdFirelists.wildrice.com] On
> Behalf Of NZG
> Sent: Tuesday, April 11, 2006 7:13 PM
> To: peteeflandvfd.org
> Cc: Marc Vincent
> Subject: Re: [ColdFire] 5282 watchdog
>
> On Tuesday 11 April 2006 5:52 pm, Marc Vincent wrote:
> > You can only write/modify the watchdog-enable bit
once after reset, ie.
> > writing 0 turns the watchdog off until the next
reset. I know its
> > inconvenient; I guess it is so you don't
accidentally turn-off the WD
> once
> > you have forced-it on (by writing 1 to the enable
bit).
>
> More than inconvient, darn near unusable since the
thing is enabled on
> reset.
> Any bootloader in it's right mind is going to turn it
off.
>
> Ah well, thanks for the verification Marc.
> I'll just build a watchdog into the my PLD,that's
easy enough.
>
> NZG
>
> >
> > HTH,
> > Marc
> >
> > -----Original Message-----
> > From: ColdFirelists.wildrice.com
[mailto:ColdFirelists.wildrice.com]On
> > Behalf Of NZG
> > Sent: April 11, 2006 5:43 PM
> > To: marc.vincentexeosystems.com
> > Subject: [ColdFire] 5282 watchdog
> >
> >
> > My bootloader disables the 5282 watchdog by
writing 0 to it.
> > For some reason, the processor doesn't seem to
enable re-enabling it.
> > Is there a way to do this?
> > Why is this?
> >
> > thx,
> > NZG
> >
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