Lpc2000

Do you have a 'loop forever' debug routine (that you can activate on 
demand) to test if your watchdog is working normally?

If your application is mission (or especially safety) critical, I 
would definitely use an external watchdog. Medical system 
requirements (In Aus anyway) require one. - also pass the reset 
signal through any external fpga or cpld to make sure that still 
works too.

Our micro, a h8 now but the next version an arm 8), has got to be in 
one of the worst environment:- our laser ps switches 900V -1000A in 
20ns! We make sure to have a excellent ground plane and all i/o off 
the board gets a schottky to rail + ground.

That's my experience. I'm keen to hear from the others designing in 
noisy environments.

Rob