Lpc2000

lhaddix wrote:
> Sten,
> What do you mean 'bad foul!!!' my design or this situation?
The situation of course! This is like building a house without a door. ;-)

> 
> I think I will add circuitry to inhibit the external watchdog
> when P0.14 is low. I also want to inhibit the external watchdog
> when my 20pin JTAG is in use. 
> 
> What can I sense to tell if the JTAG port is connected to an 
> emulator? 

Roberts idea with the JTAG-Enable pin (RTCK) is quite good. If you
pull-up this pin (e.g. LPC2138) JTAG is enabled. If this pin is
unconnected (or pulled-low) JTAG will be disabled.

> 
> I thought about counting on one of it's many grounds
> pulling a pin low, but would rather use something that didn't
> depend on certain grounds being connected inside the emulator
> pod.
Mmmmh...

> 
> I guess as Marcio points out the larger issue is why are there
> situations where the internal watchdog can't reset the micro.
> Unfortunately this is probably a feature of the LPC design.
> 
> Microchip uses an internal RC for thier watchdog which is not
> dependant of the system clock for instance.
> 
> I think what happens is it's possible for an ESD hit to stop
> the crystal osc on the LPC such that reset is needed to restart
> the oscillator, but there can be no watchdog reset without a system 
> clock.
> 
> I've considered using an external osc to feed the ARM, but don't
> wish to do this. I can't be sure it would fix the problem without
> mocking it up and then blasting with the static gun, but I know that
> toggling reset from outside will restart the clock. 
> 
> Landrum
> 

I had some similar problems with a LPC2124 last year. During ESD test
the LPC stops with and without internal watchdog. But we had another
(bigger) MCU on our board which was able to turn off/turn on the LPC if
it didn't response to hello-request packet in such a case.

  Sten
-- 
/************************************************
 Do you need a tiny and efficient real time
 operating system (RTOS) with a preemtive
 multitasking for LPC2000 or AT91SAM7?

   http://nanortos.net-attack.de/

 Or some open-source tools and code for LPC2000?

   http://www.net-attack.de/

************************************************/