A novel comparator with hamming code correction for Safety Programmable Logic Controller

Safety Instrumented Systems (SIS) are automatic systems designed for the purpose of taking an action to avoid an accident or minimize its consequences. Safety Instrumented System relies on many devices that must work as designed at a specific point in a hazard scenario to stop propagation of the hazardous event. Safety Programmable Logic Controller (PLC) plays a more and more important role in the SIS. This paper introduces a quad architecture Safety PLC, which provides complete integration within a single control architecture, where safety and standard control functions reside and work together. A novel comparator is designed with a FPGA chip, which performs hamming code correction and data bus comparison. The safety integrity level and the evaluation approach are introduced.