FPGA Implementation of Programmable Logic Controller Compliant with EN 61131-3

The paper discusses the design process of a simple programmable logic controller. The conception of the PLC is presented. The idea is to develop PLC, which is compatible with EN 61131-3 standard. This part of standard refers to programming languages. However, instructions of the PLC are directly related to the hardware structure of the PLC. The most important part of the PLC is central processing unit and the paper especially focuses on this aspect. Instruction set, encoding and some elements of the design are presented and the paper is structured to show design flow from instruction list to a hardware design. The CPU was implemented in FPGA device.