Lpc2000

Hi All

I am thinking about the protection provided by the internal watchdog 
in the LPC210x.

There is a brown-out reset controller on my board which ensure that 
the processor received a good reset when the power supply is turned 
on or dips.

Then I have activated the internal watchdog to reset the processor 
should the software make an error and get stuck in an interrupt 
routine or loop, etc. This seems to work well.

However.... What I do is put a mobile phone right next to the board 
and make a call. The board often dies and it is necessary to remove 
power and reapply it to get it to work again (after removing the 
source of interference). This means that the internal watchdog is 
not really doing its job because I would hope the board to at least 
continue with a reset so that it is not dead until some special 
intervention.

So what is happening? I wonder whether the following may be true:
- The internal watchdog is not active after a reset and it is up to 
the software to start it - which it does. 
- Heavy interference causes the board to fail and the watchdog 
fires, causing the processor to reset.
- The heavy interference is still present and so the processor is 
not running correctly.
- The heavy interference is removed.
- The processor is in an undefined state and so the software is not 
operating correctly and thus didn't restart the watchdog.
- No help comes from the (not activated) watchdog.
- This state remains indefinately (or until someone is called out 
and power cycles the equipment).

If this is indeed correct, the big question is - do I have to use an 
external watchdog after all and what level of protection / garantie 
am I getting from the internal one. In short - is the internal one 
of real use in a critical application?

Any comments or experience??????

Regards

Mark Butcher

www.mjbc.ch