Operating Mode Specific WCET Analysis

Many embedded control systems work in different operating modes, for example start-up, stand-by, shut-down and failure mode. These different operating modes usually have different timing requirements, and the different functional behaviour also leads to differences in timing behaviour. A Worst-Case Execution Time (WCET) analysis of such a system needs to determine mode-specific bounds on execution times, because a single overall bound may be too pessimistic. Mode determination and mode-specific analysis also form a prerequisite for analysing system behaviour during mode transitions, a most critical phase of a system. The operating modes of embedded control systems are often not precisely represented, neither in hand-written code nor in code synthesised by model-based design tools nor on the model level. In this paper, we outline the use of operating modes for WCET analysis. Furthermore, we describe ongoing work on semi-automatically deducing mode information from C source code and using that information in WCET analysis.