A 1.024 kHz Oscillator Clock (CLK_WDT_OSC) is sourced from the internal Ultra Low-Power Oscillator, OSCULP32K. Due to the ultra low-power design, the oscillator is not very accurate, and so the exact time-out period may vary from device to device. This variation must be kept in mind when designing software that uses the WDT to ensure that the time-out periods used are valid for all devices.
The 1.024 kHz Oscillator Clock, CLK_WDT_OSC, is asynchronous to the system clock. Due to this asynchronicity, writing to the WDT Control register will require synchronization between the clock domains.