PES and are widely used in real world. consist of hardware, firmware and application software. The PES are easily apply to many applications because its implementation has high flexibility. The PES's application are extended to safety critical systems...
PES and are widely used in real world. consist of hardware, firmware and application software. The PES are easily apply to many applications because its implementation has high flexibility. The PES's application are extended to safety critical systems such as train control system, process control system and so on. Many safety critical functions are realized through software in safety critical system. It means that a failure provokes accidents in case of the software malfunctionning. Normally, it is difficult to detect failures for PES system because the PES is too sophisticated to identify sources of the failure. The software safety ensuring arises as key problem in safety related PES applications. The safety activity of safety critical system needs to add safety activiy of software to the ordinary safety activity. In this paper, we present software safety activity and related technique for fault avoidance and fault tolerant.