In order to take advantage of the speediness of digital circuit to improve the realtime performance of protocol stack，a series of circuits are designed to implement the functions of data link layer and layer below. The network management( NMT) which determines the operational mode of communication functional unit is on the core status. A circuit for data storage and sorting is used to store the events orderly. Without changing protocol consistency， a few new main states are defined to read events from the event queue， implement the function of the NMT state machine，and do some relevant treatment after the NMT state has been changed． All of them are designed by Verilog HDL. Finally， the circuits are simulated by Modelsim SE，an EDA development software，and the correctness of the function of them is verified.