Software failure modes and effects analysis for a small embedded control system

The work shown here provides a comprehensive example illustrating how software failure modes and effects analysis (FMEA) can be effectively applied to a microprocessor based control system having little or no hardware protection. Functional, interface, and detailed software FMEAs are described. Initially, the system is described functionally and the component failure modes, which must be functional in a functional system description, are analyzed. Then the interfaces between software modules and between the software and hardware are defined and the interface failure modes are analyzed. Finally, a detailed analysis of the failure modes of individual software variables is done. Doing the analysis in this manner allows the results of the functional analysis to be used to reduce the amount of effort required for the interface and detailed analyses; similarly, the results of the functional and interface analyses reduce the effort required for the detailed analysis. One interesting result is that an analysis of the software includes certain hardware failures such as "stuck-at" and memory faults that might not otherwise be analyzed. The analysis reveals several design deficiencies for which corrections or mitigating actions are needed.