IEC 61131 and the future of PLC programming
The IEC61131-3 standard was introduced in December 1993 and since then it has been the only worldwide valid standard that defines languages for PLC programming. The five programming languages Ladder Diagram (LD), Function Block Diagram (FBD), Sequential Function Chart (SFC), Instruction List (IL) and Structured Text (ST) have different application objectives and are used individually or in any combination for the automation of machines and entire plants. With the latest state-of-the-art engineering tools, the original strengths of the languages can now be combined with the most advanced development workflows. This enables the implementation of sophisticated applications with a high degree of flexibility and security for the programmer.
The architecture of the IEC61131-3 is fully aimed at robustness and must nowadays master ever shorter clock cycles and parallel processing in addition to the hard real-time capability. Here it is definitely worth taking a look at IEC 61499 Combination of distributed programming language and legacy PLC programming with IEC 61131-3.
Industrial automation is still based on IEC 61131-3, and modern editors give the engineering environment a new touch. This makes the changeover easier even for die-hard programmers of high-level languages such as C, FORTRAN, or Pascal. In addition, engineering efficiency is increased enormously by integrating principles from modern software development, without having to sacrifice the high reliability of a real-time-capable PLC runtime. It can be assumed that IEC61131-3 will continue to be used for a long time to come in the programming of highly available and long-lasting automation systems.