Lpc2000

Cheers for the input guys.

The actual environment this board will live in is on a steel propeller shaft
rotating at up to 1000Rpm (not an ideal environment but given its job is to
measure physical parameters of the shaft somewhat unavoidable). Due to the
nature of the rotation and required freedom, power is provided by induction
from a power head mounted close to the shaft, however this can lead to
intermittent problems with power loss/surge. Surge and spikes we can deal
with electronically however power drop/loss can lead to the ramp condition
you both describe. Hence I'm looking at the potential use of an external
supervisor / WDT and wondered if anyone had had any prior experience using
them with the Philips Micros.



-----Original Message-----
From: lpc2000@yahoogroups.com [mailto:lpc2000@yahoogroups.com]On Behalf
Of unity0724
Sent: 11 March 2006 01:53
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: Use of external reset supervisor chips


Sorry, could not fully understand your question.
I was suggesting extra external hardware WDT to Mr Andrew Berney as
there might be cases of CPU not starting up, even with H/W
reset/power supervisor.  His type of working condition is just too
tough for the CPU.

If external hardware WDT is installed, this type of hardware WDT are
normally cleared by reset (Power supply below threshold level) and
will start to "WDT ticking" only after the reset (Power is above
threshold level + some reset delay).   It will always ensure some
fixed WDT timeout after reset before that WDT "bites" (typically 1-2
seconds).

For the core voltage delay, it is the duty of the reset/power
supervisor chip to have enough extra reset delay, typical 50-200mS
(extra reset delay after 3.3V power good to be longer than your 1.8V
LDO ramp delay)

Regards

--- In lpc2000@yahoogroups.com, "lpcarmed" <lpcarmed@...> wrote:
>
> I had startup issues when the power supply did not ramp up the
voltage
> fast enough. The reset supervisor will make sure you reached the
> operating voltage and then apply the delay. If your CPU is locked
up
> in a slow startup of the core voltage when peripheral supply
already
> applied the watchdog might not work. Is there a specification for
> these conditions?
>
> --- In lpc2000@yahoogroups.com, "unity0724" <unity0724@> wrote:
> >
> > Wow, very tough working condition for that Arm Chip...
> > and interesting...  :)
> >
> > May be you should use both power supervisor/monitor chip +
external
> > Hardware WDT. => WDT "kicks" the CPU again if it does not power
up
> > properly.
> >
> > I've seen some AVR chips flash program-able for WDT always on
after
> > reset.  (WDT default as on after reset)
> >
> > Could you help eMail me your experience after the project??
> > Thanks in advance!
> > Regards
> >
> >
> > --- In lpc2000@yahoogroups.com, "Andrew Berney" <amb@> wrote:
> > >
> > > Hi all,
> > >
> > > We're currently in the process of putting together a device
that
> > will be
> > > powered via an induction ring and as such there is the
potential
> > for the
> > > device to lose sufficient power intermittantly.
> > >
> > > I was wondering on peoples' general opinion of using an
external
> > supervisor
> > > chip to ensure a clean startup by keeping reset pulled to
ground
> > for a
> > > period of around 150 milliseconds.
> > >
> >
>








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