Output drive — source vs sink matters
Each I/O can sink 25 mA but source only 100 µA. Drive LEDs or small relays by sinking current from the load to ground, not sourcing from the pin. The push-pull output structure eliminates the need for pull-up resistors on outputs.
POR feature — no external reset needed
Power-On Reset (POR) initialises all I/O registers to a known state when the supply crosses the threshold. This eliminates the need for a dedicated reset pin and external RC circuit.
