Window Watchdog (Wwdg) - STMicroelectronics STM8 Manual

Window Watchdog (WWDG)

The WWDG is a bit more advanced watchdog timer. Unlike the IWDG, it will trigger a reset condition
if its counter is reloaded earlier or later than a predefined time window. This kind of timer is usually
found in high-end microcontrollers like ARMs, ATXMegas and recently released micros. Cool features
like this and others make me feel that indeed STM8s are high-end affordable 8-bit alternatives when
compared to traditional 8-bit MCUs.
The WWDG works by comparing a down counter against a window register. The counter can only be
refreshed when its value is greater than 0x3F and less than window register value. If the counter is
refreshed before the value set on window register or when the counter is less than or equal to 0x3F.
If the counter hits the value 0x3F, reset automatically triggers. It is programmer's responsibility to
refresh the counter at proper time. Note unlike IWDG, WWDG is not independent of main clock.