At 02:02 PM 6/8/01 -0700, you wrote:
>erk... I knew that, I was just testing you.

Good save.

>Duh! If the processor went nuts, it could easily disable the WDT, which
>would make it useless. Of course, there is nothing that prevents a whacked
>out processor from getting stuck in a loop where the WDT is constantly being
>reset either, but I suppose that would be a lot less likely.

Yup, and as the programmer you can *make* it less likely by not doing
silly things like resetting the WDT in a timer interrupt routine, by doing
some basic checking to see if things "seem" to be ok, before resetting, that
sort of thing. Even if the WDT requires resetting at a higher rate than
the most complex operations in your program, you can have a countdown
timer that inhibits the WDT reset if, say, an important result is not
delivered every few seconds.

The PIC has a circular buffer for the hardware stack, so this
isn't a consideration for PICs, but on some processors I write a "canary"
byte past the end of where the stack should end (in RAM). If the stack
grows too far for some reason, it over-writes the byte (which is only set
at power-up) and the WDT eventually resets everything.

Best regards,

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.