Is a watchdog timer appropriate in a radio?

Paul E. Bennett wrote:

> Kevin D. Quitt wrote:
> 
>> On Mon, 11 Apr 2005 14:08:24 GMT, Michael <NoSpam@att.net> wrote:
>>>Which is why it's a good idea to make that watchdog hardware untouchable
>>>by
>>>programmers.  In the case I cited, the watchdog implemented as little
>>>more than a binary counter and a bit of glue.
>> 
>> Something has to feed the dog cookies to keep it from going off.  This is
>> usually something in the idle loop of the OS or application.  Where this
>> code is, and exactly how it works isn't something for a novice to decide.
>> If the status of the system can be verified externally, that's much
>> better.

Sorry about that. I seemed to have hit the send key when the phone rang. 
I'll pick up where I left off.
 
> I consider that the output to kick the watchdog should only be proferred
> when the complete set of sanity checks of the system operation have proved
> to be in the "sane system" region. For me that means really reading its
> inputs, still in control of its outputs and having no other detectable
> errors. I use a pulse maintained relay circuit that is wired to drop 
output power if the state of its input is not inverted at regular 
intervals. The circuit is configured such that any single component failure 
is almost certain of achieving the outputs powered down state.


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Paul E. Bennett ....................<email://peb@amleth.demon.co.uk>
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