Electronic apparatus and operation method thereof having a low power wake-up mechanism

An electronic apparatus operation method having a low power wake-up mechanism used in an electronic apparatus, comprising:

• powering off an upper layer circuit in a sleep state;
• waking up the upper layer circuit in the sleep state by a physical layer circuit according to a logic state transition event that indicates a pair of differential signal lines of a Universal Serial Bus interface transiting from a sleep logic state to a wakeup logic state, such that a power of the upper layer circuit is restored, wherein the pair of differential signal lines electrically couple the physical layer circuit to a host apparatus;
• determining, by the physical layer circuit, whether the physical layer circuit comprises a state storage area configured to store a previous state of the upper layer circuit before the upper layer circuit is powered off;
• modifying a voltage state of the pair of differential signal lines by the physical layer circuit to drive the host apparatus to detect a pull-out event and a plug-in event in a sequential order when the physical layer circuit does not comprise the state storage area;
• and controlling the upper layer circuit by the physical layer circuit to perform an initialization and enumeration process with the host apparatus to reconnect with the host apparatus;
• and
• not modifying the voltage state of the pair of differential signal lines when the physical layer circuit comprises the state storage area and directly controlling the upper layer circuit to retrieve the previous state of the upper layer circuit from the state storage area by the physical layer circuit to reconnect with the host apparatus.