The Realization Of Ladder Diagram Software In PC And Displaying Arithmetic Based On The Standard IEC61131-3

The article generally introduces the development history of PLC and the standard of IEC61131, the content of the standard of IEC61131, five types of programming language based on the standard IEC61131-3, software model structure, and the present situation of domestic and international PLC development, then introduces the structure and run mechanism, then narrates the realization of designing PLC with ladder diagram language based on the standard IEC61131-3, the project includes the design of total structure and data structure. The total structure contains the design of PC software and the design of the software and hardware in AVR. PC software includes the modules below: project management module, editor module, debug module, arithmetic module and serial communication module. The integral structure is designed independently, mainly divided into three layer data structures, the first layer data structure is the form of struct array, every struct element contains the information of every element; the second layer data structure is the form of binary instructions, we design arithmetic to translate first-class codes into second-class codes; after optimizing the second layer data structure, we form the third layer data structure, third-class codes are stored in RAM, the system software we devoloped in FLASH execute third-class codes step by step, controlling distant I/O modules. Then the article analyses the structures of first-class codes and second-class codes, the arithmetic of translating ladder diagrams into first-class codes and transforming second-class codes to ladder diagrams. At last, the paper explains the realization of serial communication between PC and AVR.The project is completed by three persons. I mainly take charge of designing PC software and three layer data structures, translating the ladder diagrams into first-class codes, transforming second-class codes to ladder diagrams and the design of serial communication in PC software. The article is very important to develop homemade PLC system.