Study on fault-diagnosis and testability design for microprocessor-based railway signalling equipments

This paper first analyzes the algorithms for testing microprocessors, static random-access memories (RAMs), read-only memories (ROMs), and input/output interfaces (U/O), and selects the suitable ones for the signaling equipments. Then, the systems´ fault-diagnostic methods are presented. They include the self diagnosis for being powered on, the static self-diagnosis for maintenance and the dynamic self-diagnosis for the system operation. By adding appropriate testing points to improve each board´s controllability, and by combining with the static self-diagnosis programs to locate most faults, the system´s maintainability is improved