Well, OK, how about a temporary test circuit:  set a momentary contact
switch on an input pin.  Write a btfss debounce loop to read the pin
without a CLRWDT in it (light up an led or beep something to
confirm).  Prescale the WDT to max.  Fire up the circuit, and tap the
button.  the light should flash.  Now restart, and hold down the
button.  Because there is no CLRWDT, the thing will crash and
restart.

For more entertainment, write a loop for a 2-minute sleep delay.
Measure delay with stopwatch.  Now, using hair dryer, heat up the
circuit and measure the same delay.  Then move outdoors, and stand
outside shivering in the dark for half an hour and measure the sleep
delay again.  There are resistive elements in the pic, and resistors
change resistance with temperature.

alice


> So you have completed your design, and now comes the testing.
> How do you test such a design to prove that the WDT is working
> correctly?
>
> Do you zap the PIC with some electricity and see if it has regained
> control correctly?
> Flood it with intense noise that is sure to freak out some of its
> transistors?
>
> This is where a true hardware ICE probably comes into play (for those
> that can afford them).
>
> In addition, can someone explain the drift with regards to temperature
> that a WDT on
> a PIC (eg. 16F84) can have?  I would like to understand more of it and
> eventually incorporate
> the WDT usage in my designs, but not if its too unstable.
>
> Reliability is the key here.
>
>
> Thanks.
>
>
> - Sebastian
>
>
>
> > -----Original Message-----
> > From: Harold M Hallikainen [SMTP:haroldhallikainen@JUNO.COM]
> > Sent: Tuesday, October 26, 1999 12:47 PM
> > To:   PICLIST@MITVMA.MIT.EDU
> > Subject:      Re: watchdog timer
> >
> >         In terms of computers (including PICs), I don't think it's a
> > question of IF they will crash, but more a question of WHEN they will
> > crash.  Having a WDT allows the system to recover from the crash.  I
> > once
> > had to drive 100 miles through Kansas in the middle of the night to
> > hit
> > reset on a system I built to control broadcast transmitters so the
> > station could go back on the air at 6am.  EVERYTHING I've built from
> > then
> > on includes a watchdog timer...
> >
> > Harold
> >
> >
> >
> > Harold Hallikainen
> > harold@hallikainen.com
> > Hallikainen & Friends, Inc.
> > See the FCC Rules at http://hallikainen.com/FccRules and comments
> > filed
> > in LPFM proceeding at http://hallikainen.com/lpfm
> >
> > ___________________________________________________________________
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