Abstract: A network device including an address move detection unit, a loop detection packet generation unit, a packet parser unit and a loop determination unit coupled to the packet parser unit is provided. The address move detection unit detects whether an address field of a first packet received by the network device is moved. The loop detection packet generation unit generates a loop detection packet if the address move detection unit detects that the address field is moved. The packet parser unit parses a second packet received by the network device to extract an information. Based on the information, the loop determination unit determines whether the second packet matches the loop detection packet so as to determine whether there is any loop existing in the network device.

Abstract: The present invention relates to a phase detector with no dead zone comprising two detecting means and two control logic circuits. The phase-frequency detector employs the control logic circuits to proceed with reset operation of the detecting means such that the existence of a phase difference between the reference clock signal and the feedback clock signal prevents the misdetection of the up, down signals (output signal), and the up, down signals will not be simultaneously at "1".