A Software Framework for Hard Real-Time Distributed Embedded Systems

The paper presents a framework for distributed embedded applications that can be used to engineer open, and the same time, predictable embedded systems. Applications are composed from components (actors), which communicate transparently by exchanging labeled messages (signals) over a real-time network. The signals are exchanged at precisely specified time instants, in accordance with the Distributed Timed Multitasking (DTM) model of computation, resulting in the elimination of task and transaction I/O jitter. DTM is supported by an operational environment, which has been integrated with application components in an implementation model specifying explicitly the composition of software nodes allocated to physical network nodes. The framework is characterized by complete separation of computation and communication, whereby communication is delegated to the timed-multitasking operational environment. This has resulted in a simplified application model in which actors have been reduced to actor tasks composed of prefabricated components, such as state machine and action function blocks.