Lpc2000

--- In lpc2000@yahoogroups.com, "Rick Collins" <gnuarm@a...> wrote:
> 
> --- In lpc2000@yahoogroups.com, "tah2k" <tah2k@y...> wrote:
> > 
> > When enabled and timed out, the LPC2138 watchdog with generate an 
> > interrupt and may cause a reset depending on the state of 
> > WDMOD:WDRESET bit.
> > 
> > I can see the interrupt being useful during debugging when the reset 
> > is disabled, but does it serve any purpose when the reset is 
> > enabled? Would the ISR even get serviced if the watchdog times out 
> > and a reset is forced?
> 
> I think the idea is that you can either reset the chip, or you can 
> use the interrupt.  I don't know why you would use the interrupt 
> instead of the reset, but I have seen PC based embedded systems that
> use a normal timer interrupt as a watchdog when no watchdog hardware
> was available.  It was more of a way to detect that one of the tasks
> was not responding.

Hi,
using the watchdog with interrupt has two options, you use it as a
periodic timer interrupt or for debugging, if it ever hits you know
that your application is not feeding the watchdog frequently enough.

For the reset, this should be default in a running and debugged
application. The idea behind the watchdog is that e.g. your main loop
services the watchdog and if your program execution becomes undefined
the program will not longer return to the lowest priority main loop.
The only way to get out is probably a reset. This is what the WDT will do.

hth Bob