At 11:43 AM 4/8/97 +0000, you wrote:
>>>  I
>> >don't think, though, that a WDT will help much in a noisy
>> >environment.
>
>>  Thanks,Lawrence.But if WDT isn't usefull for that,then what is it
>>  there for?
>>                    Walter.
>>
>My understanding is that the WDT will mostly protect the chip from
>software related glitches.  Anyone else have a clear idea?

how do you "glitch" in software?

WDT is usable when the cpu has been 'upset' and not executing
user code any more. This may happen if the internal registers
have corrupted by noise on VCC or by other means.

It may also be work when the software likes the "runaway"
melodie, ie jumps to where it was not supposed too, and
stays there in a loop long enough for WDT to trigger.

If a program is written correctly and does not trigger
WDT timeouts for some special purpose (like power saving
mode used by Stamps) then WDT timeouts should not occour
during normal program execution.

WDT does not help against Brown Out situation where some
RAM registers are destroyed but cpu continues to work
without performing a full hardware reset.

a program that runs with WDT enabled and has CLRWDT in
every possible loop, is making no actual use of the WDT
protection. CLRWDT should be used only in important places
that are executed during normal work.

antti


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