On Fri, 8 Jun 2001 15:37:31 PDT, William Chops Westfield wrote:

>I think it's the Atmel parts (and perhaps other) where software can tur=
n
>on the watchdog timer, but not turn it off.  So you turn it on in
>initialization (if you want) and then have to reset it periodically,
>but bogus code can't cause it to be turned off accidentally...

Not *quite* accurate... to quote the data sheet:

  Bit 3 - WDE: Watchdog Enable
When the WDE is set (one) the Watchdog Timer is enabled, and if the WDE =
is cleared (zero) the Watchdog Timer function
is disabled. WDE can only be cleared if the WDTOE bit is set (one). To d=
isable an enabled Watchdog Timer, the following
procedure must be followed:
1. In the same operation, write a logical "1" to WDTOE and WDE. A logica=
l "1" must be written to WDE even though it
is set to one before the disable operation starts.
2. Within the next four clock cycles, write a logical "0" to WDE. This d=
isables the Watchdog.

>
>BillW
>
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>

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