The STWD100 watchdog timer circuit is a standalone device that prevents system failures caused by certain types of hardware faults (such as unresponsive peripherals, bus contention, etc.) or software errors (such as incorrect code jumps, code stuck in loops, etc.). The STWD100 watchdog timer has an input pin WDI and an output pin WDO (overline). The input pin is used to periodically clear the internal watchdog timer within the specified timeout period twd.