FPGA Implementation For The Communication Node Of Modbus Protocol

With the rapid development of the computer technology the industry has entered the era of electronic information and the 4.0 industry of the future from the era of electrification and automation. Factories use a large number of machineries and equipments controlled by the embedded system of automation information technology to manufacture products. It makes an unprecedented increase in the production efficiency of the plant, pass rate and the life of machinery and equipment.In order to improve Ethernet device is not easy to expand, the reaction is not fast enough, the hardware is not easy to replace and the limit of interface speed in the factory. This thesis describes the method of the Modbus protocol communication nodes based on FPGA through the software and hardware.Firstly, the thesis introduces the development and background of the communication protocol of Modbus. This paper also describes the development direction of field bus in the world. At the same time, it states the principles and applications of the Modbus model, it also details the implementation of transmission,the message frame structure, the communication between master and slave and definition of function code about the Modbus protocol. Then the difference between FPGA and CPLD is explained in the thesis, and the board of FPGA is chosen to use.We select the DE2 board of FPGA as the hardware, it is Altera's products that using the 2C35F672C6 chip based on the Cyclone II platform. SOPC system is constructed based on Nios II IDE software in the FPGA development board, we add the UART module through the costom bus, at the same time it support to modify the parameter of the baud rate, parity error check, data bits and stop bits in the software.In addition, it configured the Flash, SDRAM, I/O interface, timer, and other peripheral equipment. The method of functional modules is used to develop the Modbus communications network based on soft-core of IP, and we develop severalfunction performances, such as timers, UART, message processing and callback.In conclusion, this article has realized the SOPC system through FPGA, we implement the Modbus network protocol based on C language on IP soft core. Lastly we put forward the master-slave communication that can support the standard Modbus protocol.