Development Of Modbus RTU Slave Station Module Based On FPGA

Modbus Fieldbus applications expand quickly in the field of industrial due to its advantages of stablity, reliablity and convinent-link. It is of significant practicability and applicability for the development of typical Modbus slave station module. However, the existing Modbus product is expersive and the applications is limited. Thus, a novel Modbus RTU slave station based on FPGA is designed and implemented to promote the universality and cost-effective rations of Modbus product. The main contents of this thesis are as follows:The function requirements of typical platform for industrial control areas are analyzed. Then, a FPGA-based Modbus RTU salve station is proposed. In addition, the hardware platform is designed followed by the detailed principles introduction of the key modules for this platfrom.Based on the hardware platform, data processing of Modbus communication IP core and state machine are presented. Considering of modular programming ideas of FPGA, the design and test of main modules are accomplished, which consist of data receive/send module, error detection, abnormal response module and function code module. In order to improve the communication stability, a mechanism on the basis of oversampling technology is put forward.According to the function requirements of the platform and the designed Modbus communication IP core, application interface modules are designed including I/O input and output, AD/DA, matrix keyboard, matrix LED, pulse transmission and encoder receive module. Futhermore, a pulse transmission algorithm is proposed to solve the pulse width mutations problem which leads to dithering phenomenon.Finally, cooperated with filedbus IO, matrix keyboard, Pulse adapter, PC machine, servo driver and incremental motor, experimental platform of the Modbus RTU slave station is built. Functional test and reliability test are conducted. The results verifies the validity and effectiveness of the proposed Modbus RTU slave station.