Abstract: A media access control (MAC) circuit is coupled to a physical layer circuit and includes a storage circuit, a receiving circuit, a checking circuit, and a protection circuit. The storage circuit is configured to store a first value and a second value. The receiving circuit is configured to receive a packet from the physical layer circuit. The checking circuit is configured to check the packet. The protection circuit is configured to perform the following steps: updating the first value according to a clock; and discarding the packet when the absolute difference between the first value and a reference value is smaller than the second value.

Abstract: A method for scanning a keyboard circuit is provided. The keyboard circuit includes a keyboard array, output wires, input wires, and a scanning circuit. Each of the output wires is electrically coupled to a corresponding column of key units of the keyboard array, respectively. Each of the input wires is electrically coupled to a corresponding row of key units of the keyboard array, and is provided with a pull-up resistor. The method includes: turning on and connecting open-drain transistors to the ground in a scanning interval to clean charges on the output wires; turning on the open-drain transistors and connecting the open-drain transistors to the ground sequentially in a scanning duration; and receiving detected electrical levels through the input wires, and when one of the detected electrical levels is substantially equal to the electrical level of the ground, determining that the corresponding key unit is pressed.

Abstract: A method for scanning a keyboard circuit is provided. The keyboard circuit includes a keyboard array, output wires, input wires, and a scanning circuit. Each of the output wires is electrically coupled to a corresponding column of key units of the keyboard array, respectively. Each of the input wires is electrically coupled to a corresponding row of key units of the keyboard array, and is provided with a pull-up resistor. The method includes: turning on and connecting open-drain transistors to the ground in a scanning interval to clean charges on the output wires; turning on the open-drain transistors and connecting the open-drain transistors to the ground sequentially in a scanning duration; and receiving detected electrical levels through the input wires, and when one of the detected electrical levels is substantially equal to the electrical level of the ground, determining that the corresponding key unit is pressed.