LPC15xx, WatchDog Timer, what is window concept?

[richardpayne]

I wish to implement simple WDT which basically reset the MCU in case of crash or bug (freeze).

I struggled window concept part, in any I could not find sufficient how this window work to make sense, lack of demo is the problem and why to use it. I read your manual several time and sorry I do not get it. 

Do you have something better to explain this?

[Hui_Ma]

Hi

As the user manual mentioned about WDOG window conception below:

When a watchdog window is programmed, an early watchdog feed is also treated as a watchdog event. This allows preventing situations where a system failure may still feed the watchdog.

So using below picture as an example:

Fig47 is early watchdog feed issue, for the watchdog windowed mode enabled. The watchdog counter count down with watchdog clock, the counter start value is 0x2000 and Feed Window start value at 0x1200. If the watchdog counter value big that 0x1200, such as picture shows 0x1257 with a watchdog feed action, which is a early watchdog feed behavior will be treated as a watchdog event (reset or generate interrupt).

If there set the Window value to 0x2100 with watchdog counter start value 0x2000, there could not exist early watchdog feed behavior.

Fig 48 is the correct watchdog feed behavior. The feed action happens within Window counter (watchdog counter 0x11FC value is smaller than Window set value 0x1200 )

Wish it helps.

Have a great day,
Ma Hui
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