Timing Definition Language (TDL) Modeling in Ptolemy II

This work presents a modeling and simulation platform for embedded control systems where real-time requirements are explicitly specified in the system model by using the Timing Definition Language (TDL). TDL employs the Logical Execution Time (LET) abstraction to specify platformindependent execution times of periodic time-triggered computational tasks, with the main aim of achieving time and value determinism of composable embedded software. For a certain execution platform, this aim is attained if the software components can be suitably scheduled for execution so that the LET specifications are satisfied. In general, an embedded control system contains also concurrent computations triggered by environment conditions (dynamic events), which share the same execution platform. This makes static schedulability analysis for the LET-based part hard to achieve. Thus, a simulation platform is needed to investigate the interaction between time-triggered components and components triggered by dynamic events. We have implemented such a simulation platform by extending the Ptolemy II framework, thus leveraging models of computation that are already available in Ptolemy II, such as the modal model and the discrete event domains.