This slide shows the operation of the watchdog timer using the window size (the green area) which here has been defined as 50%. When the window is opened the watchdog timer can be retriggered after it has reached 50% of the overall overflow time. If the retrigger is too late, i.e. the overflow time has been reached, an interrupt will be generated. Using the window function, if the retrigger comes too early (before 50% of the complete overflow time) the reset will be generated. Other operations that cause a reset from the watchdog timer are when an incorrect magic word is written to the WDTE register or when a bit operation is attempted on the WDTE register.