Research And Realization Of ATM Switch Unit Of Fast Lookup Table Based On Knockout Switch Fabric

Information times, communication networks have become very important media for transferring information. In traditional communication mode, Voice, Data, Image and Video are transferred by communication networks with different transfer property. With the development of society, single characteristic network can't satisfy the demand of modern communication, all kinds of information need speedily transporting in single network, therefore Integrated Services Digital Network (ISDN) is put forward. Now B-ISDN based on fiber has been the major trend. As a core transfer mode of B-ISDN, Asynchronous Transfer Mode (ATM) can dynamically allot and make the best of frequency band of channel, and fulfill high-speed, high-throughput and high-QoS information exchange. As a result, it is widely used.ATM switch fabric is one of the key technologies of realizing ATM switching. In this paper on the basis of thoroughly researching the basic principle of ATM, ATM switch fabric, the control principle of ATM switch fabric and design principle of multistage switching network, a design method that is based on Knockout switch fabric and makes use of lookup table to achieve ATM switching is brought forward. The method uses a N2 separate access, modularization and nonblocking interconnection frame. The frame is easily fulfilled, and its inputs have high transfer rate. ATM switch fabric based on the algorithm of speediness lookup table and VHDL is designed by this method. In this design lookup table is used, and improves the lookup efficiency and reduces the demand for the process rate. In this paper a hierarchical design method of Top Down is adopted, all of function blocks of ATM switch unit are described by synthesizable VHDL, and are functionally simulated and logically synthesized, so 8×8 ATM switch unit is obtained. According to this unit, n×n ATM switch unit and multistage switch network are also obtained. In this design Modelsim 5.6 is used as the simulation software, and synthesis software is Quartus II 3.0, by which the design entry, function simulation, timing simulation and device programming can be done. By simulating the switch unit, it can be seen that ATM switch unit that is designed by use of hierarchical design of top down with VHDL can perform the basic function of cell head changing, routing and queuing. If many cells race one output channel, the ATM switch can put these cells into a buffer, then queue and output them. When the broadcast cell advents, it can be delivered to all channels.