Safe PLD-based programmable controllers

In many industrial processes, an incorrect operation can lead to irreparable damage to people, equipment, or the environment. In order to reduce risks, the electronic control systems used in this kind of processes must comply with international standard safety requirements. The safety market solutions are mainly based in the use of high-end programmable logic controllers (PLCs) and/or application specific integrated circuits (ASICs) for concrete processes or machines. The solutions proposed in this paper are based on the implementation of safety redundant control systems in programmable logic devices (PLDs and FPGAs). The proposed methodology for safe controllers design is based on the combination of dynamic logic and redundant circuits with voting capabilities. The use of programmable logic devices (PLDs) instead of high-end programmable logic controllers (PLCs) adds flexibility to the design of safety-related control systems and reduces costs, while maintaining high reliability and a good degree of failure detection.