The Communication Technology Research Of Soft PLC Based On FPGA

Soft PLC overcomes some disadvantages of the traditional PLC,such as closed hardware system,disunity software programming standards.It is widely used in industrial control.But with the development of information and control technology,soft PLC's load about communication(Field bus,HMI,special communication needs,etc.)is growing.Coupled with the control logic of soft PLC gets more complicated,the processing performance of soft PLC which is based on the traditional "general processor + real-time system " system architecture is facing challenges and the bottleneck of enhancing.FPGA has the advantages of high-speed,parallel and programmable.The application of FPGA in the field of bus communication can solve some practical problems encountered in the research of soft PLC.The research contents of this paper are as follows:On the one hand,the control requirements of complex communication process in redundant soft PLC system are analyzed,and the communication control scheme based on FPGA(the FPGA device is referred to as redundant bridge)is proposed.On the other hand,against the instability of Modbus RTU bus communication in a kind of soft PLC which is running in the domestic processor,the Modbus RTU slave based on the FPGA resource of the processor is proposed.According to the overall design of redundant bridge,the design work of the simple Ethernet MAC controller and Ethernet-CAN converter is discussed.On this basis,The soft PLC duplex and state synchronization control mechanism is been thoroughly studied.And the design work of relevant functional modules have been completed.According to the overall design and Modbus RTU protocol,the design of Modbus RTU serial link communication module and Modbus RTU protocol processing unit is completed.In order to ensure the security of the data stored in the holding registers which is realized based on dual-port RAM,a secure access mechanism is proposed.Finally,a series of experiments is designed to verify the research production of this paper.On the one hand,some experiments are designed to verify the technical performance of the redundant bridge and its sub-modules.The experiment results shows that the redundant bridge has realized the design functions and its reliability has been basically verified.On the other hand,some experiments is designed to verify the technical performance of the Modbus RTU slave.The experiment results shows that the Modbus RTU slave basically conforms to the Modbus RTU protocol standard and realized the design target.