During the operation of the safety digitalized instrument and control system of nuclear power plant, it is necessary to monitor the data of online operation in real time. The communication between the engineer station and the safety level shall ensure the real-time, accuracy, reliability and safety requirements of data monitoring. How to design the maintenance network between non-safety engineer station PC and safety instrument and control system is a difficult problem in the industry of nuclear safety DCS research and design. The FirmSys is the first digital nuclear safety instrument and control system platform successfully developed and appraised in China. This paper is based on the networking characteristics of the data communication network in the FirmSys. A data real-time monitoring design based on 802.3 protocol is proposed. The design is based on standard MAC frame structure, and a new data frame format is formed by adding new data segments to meet the real-time requirement of network node interaction. Then, different communication instruction function codes and fixed communication flow are designed to meet the accuracy requirements of the data, and finally, the communication security requirements are met through CRC check, function code check and communication error check. After testing, the method has the characteristics of high real-time performance, high data accuracy and low configuration requirement, and can meet the requirements of real-time data monitoring of nuclear power instrument and control system, and can also be applied to industrial control fields such as ships and thermal power plants.
