Design of PLC Sequential Function Chart Based on IEC61131-3 Standard

Abstract

According to the requirements of IEC61131-3 standard, the system of Programmable Logic Controller (PLC) using Sequential Function Chart (SFC) as the main programming language is build. Aiming at the requirements of the SFC programming system, the framework of SFC is established, on this basis, a suit of data structure based on Object-Oriented thinking is designed. It describes the data structure of SFC mainly, and in this way, the functions of SFC, including edit, modify and compile, etc, are realized.The syntax check and logic check of SFC are achieved by traveling recursively and iterating the layers of the nested data structure of SFC. After making SFC into intermediate code, eventually the intermediate code is translated into the corresponding object code.