| In order to realize process control and state management of avionics system,resource sharing among subsystems or modules,reduce the weight of interconnected media,reduce complexity,and improve the real-time and reliability of information transmission.Moreover,avionics systems often work in harsh environments such as high altitude,high temperature,high speed,and strong electromagnetic interference.It is urgent to seek a reliable communication method.The time division command/response multipath data transmission bus(MIL-STD-1553B)communication protocol emerged in this context and perfectly solved these problems.MIL-STD-1553 B adopts half-duplex communication mode,which can effectively integrate system communication and adopt integrated control.Due to its high reliability,high speed and high stability,the protocol was originally applied to aircraft avionics systems in the United States.The application has basically covered the whole world and has become an international standard.The MIL-STD-1553 B communication network is mainly composed of a bus controller(BC,Bus Controller),a remote terminal(RT,Remote Terminal),and a bus monitor(Bus monitor).The bus controller is responsible for controlling the entire MILSTD-1553 B communication network.It is the only terminal on the bus that is configured to perform setup and start data transmission,that is,the initiator of all communication events on the bus,responsible for initiating communication commands.The remote terminal is the interface of the user subsystem to the data bus,and is always a passive receiving command,that is,responding to commands sent by the bus controller(except broadcast messages),it only receives the transmission sent by the bus controller.The data is sent to the bus only after the command word.The bus monitor monitors all transmitted messages on the bus to complete the recording and analysis of the data source on the bus,but it does not itself participate in bus communication.Considering that the 1553 B bus does not have an off-the-shelf IP(Intellectual Property)core available in the FPGA,this paper mainly uses the logic code language Verilog to realize the functions of the three terminals of the 1553 B bus,and refers to the protocol of 1553 B.To realize the transmission and reception of ten kinds of message types,so as to verify the feasibility of the whole 1553 B system,and draw on the scheduling method of FlexRay bus to realize the scheduling control of its messages,so that the scheduling of messages is more flexible.The work of this paper mainly completes the system design based on MIL-STD-1553 B communication protocol.The logic design and implementation of BC,RT and BM are completed by Field-Programmable Gate Array(FPGA).Previous hardware limited the traditional 1553 B bus rate to 1MB/s,and today’s better devices enable bus speeds of up to 10MB/s and 20MB/s,and the bus speed can be switched between the two;updating the original 1553 B network The topology structure uses an optical line terminal(OLT,Optical Line Terminal)and an optical network unit(ONU,Optical Network Unit)to implement data transmission and reception of each module,and is suitable for cascading of multiple subsystems;The new message scheduling mode uses a periodic scheduling area and an aperiodic scheduling area to send messages in a small period,making the entire 1553 B bus system more reliable and faster. |
