Research On Key Technology Of Token Bus-oriented Testing

With the continuous development of information technology,the amount of data in the airborne electronic equipment system is getting larger and larger,and the data blending becomes more and more frequent.It is necessary to explore a new type of bus as the medium of information transmission between electronic equipment,which is the nerve center of the system,organically connects physically dispersed electronic equipment,realizes mutual coordination and sharing of system information,and makes the system huge and complex Reliable and efficient transmission of data information.Because the distributed topology has higher reliability,it is more suitable for aircraft,missiles and other equipment.According to the survey results of multiple institutions,the best bus solution supporting the distributed topology is the token medium access control method.This control method can accurately transmit information to the destination node,and has high reliability,determinism and fault tolerance.However,due to the current lack of test methods,test specifications and test instruments for the token bus,it has produced huge resistance in application,and it is of great significance to study the corresponding bus test technology.Based on this,this article explores the token bus test technology.First,the Token Bus(IEEE802.4)standard protocol is deeply studied.In order to facilitate the test of the protocol content,the Token Bus control node is designed,and the nodes are connected together using RS-485 to construct the Token Bus.Taking this as the test object,the test technology of the token bus is explored.Then,with reference to a large number of bus testing related literature and the testing requirements and methods of Manchester code,the testing requirements and testing methods of the token bus are studied and analyzed.A test procedure suitable for the token bus is proposed,including the physical layer and data link layer of the IEEE802.4protocol.Finally,according to the proposed bus test requirements and bus test procedures,a token bus test system was designed,and the prototype of the token bus test principle was developed.Waveform acquisition can be performed according to the bus test requirements.When the frame start delimiter is monitored,the set multiple bus waveform parameters are compared with the actual waveform,and the waveforms that exceed the range specified by the test procedure are captured and stored.Based on the above research,using simulation and experimental verification,first use the Modelsim simulation tool to perform joint debugging and joint test simulation on the various modules of the token bus control node.After the node receives a valid frame,it can make corresponding state transitions,which conform to the token bus The agreement stipulates.Use the test principle prototype to test some test items of the constructed bus,which can complete the waveform acquisition of the frame and generate the test results.