What is the main function of Watchdog Timer (WDT) controller?

[Henry]

The purpose of Watchdog Timer is to perform a system reset when system runs into an unknown state.
User needs to clear the WDT counter before the WDT controller resets a chip if the chip is operating normally.
Moreover, user can also use the WDT interrupt event, and use the WDT wake-up function to wake up the CPU from Power-down mode.