Fault insertion testing of a novel CPLD-based fail-safe system

According to the standard IEC 61508 fault insertion testing is required for the verification of fail-safe systems. Usually these systems are realized with microcontrollers. Fail-safe systems based on a novel CPLD-based architecture require a different method to perform fault insertion testing than microcontroller-based systems. This paper describes a method to accomplish fault insertion testing of a system based on the novel CPLD-based architecture using the original system hardware. The goal is to verify the realized safety integrity measures of the system by inserting faults and observing the behavior of the system. The described method exploits the fact, that the system contains two channels, where both channels contain a CPLD. During a test one CPLD is configured using a modified programming file. This file is available after the compilation of a VHDL-description, which was modified using saboteurs or mutants. This allows injecting a fault into this CPLD. The other CPLD is configured as fault-free device. The entire system has to detect the injected fault using its safety integrity measures. Consequently it has to enter and/or maintain a safe state.