Watchdog device driver

[Andrei Chichak]

At 10:12 PM 5/21/2008, you wrote:
>I think a single call to RESET or SERVICE the watchdog is all that is needed.

Needed perhaps, but I have been using a safer(?) harder(?) system 
where the watchdog is half strobed, the main processing of the system 
is done, then the second half of the strobe happens. On a processor 
like the 68332 the sequence must be exactly a write of 0x55 then 0xAA 
in that order, so if you miss the second half of the strobe and do 
the first half again, the processor resets. You get another sanity 
check for cheap.

The Motorola 68HC12 series they have a windowed COP mode where the 
second part of the strobing has to happen in the last 25% of the COP 
timeout period, strobing within the first 75% will cause the 
processor to reset. This is used to ensure that the system does not 
run too fast (a process went away, pll not correct, temperature issues???)

That is why I think a pair of half service calls is better.

Andrei