The Firmware Development Based On Domestic PLC Slave And Application Research Of CoE Protocol

In recent years,there have been many information security issues in the field of industrial control.At home and abroad,there have been a large number of attacks on industrial control system,which has sounded the alarm for the information security of industrial control system in China.So it is of great significance to achieve the localization of alternative industrial control products.The national PLC(Programmable Logic Controller)is a kind of industrial control product which is designed to deal with information security threats to achieve the purpose of autonomous control.It takes use of modular design,in which the host computer achieves the configuration of the PLC master station and the master station achieves the real-time control and diagnosis of the PLC slave station,while the specific logic function is realized by the PLC slave station.Thesis completes the firmware development of the PLC slave I/O modules and implements the application layer CoE(CANopen over Ether CAT)protocol.Firstly,it analyzes the necessity and urgency of realizing PLC domestic substitution,and briefly introduces the development status of PLCs at home and abroad as well as the application of different industrial Ethernet.From the point of view of timeliness and synchronization of the bus,the Ether CAT(Ethernet Control Automation Technology)bus is selected as the communication b us between the PLC master and slave stations.It uses the dedicated hardware to realize the sending and receiving of the Ether CAT data frame,and the response time can be realized in milliseconds,which meets the real-time requirements of the industrial field.Secondly,the Ether C AT application layer protocol is briefly described.From the point of view of current application requirements,thesis proposes a scheme to implement CoE protocol of application layer.Compared with other application layer protocols,this protocol has the characteristics of high reliability and timeliness.O n the basis of deeply analyzing CoE protocol,a unified interface for the application is provided by means of the station dedicated processing chip.Then,on the basis of deep understanding of the characteristics of PLC slave system and SPARC architecture,an analysis of detailed application requirements is made for four slave modules,including digital input,digital output,analog input and analog output slave modules.Combined with the logic function of each slave module,a detailed software program is designed to achieve the process data communication and mailbox data communication,which is based on modular design principles and developed by the use of embedded C language.Slave code not only implements the logic function,but also has good readability and portability.Finally,a simple test environment is built to test each I / O slave module.In order to ensure the communication function of the master and slave station is normal,a communication function test about the CoE protocol is carried out to verify the response mechanism of the master station request datagram and the slave response datagram.A total of four slave modules are tested for logic functions,including digital input filtering,digital output diagnostics,analog calibration,and emergency events.The analog input / output modules are calibrated using the least squares method to achieve industrial conversion accuracy requirements,and the error after calibration does not exceed 0.05% FSR.The test results show that the PLC slave not only realizes the normal communication with the Ether C AT master station,but also uses the CoE protocol to achieve the purpose of the master station to configure the slave station flexibly and realize the accurate data exchange with the slave station,which tests the correctness of the PLC slave hardware circuit and reliability of the basic control functions of the peripherals.In general,it meets the expected design requirements.