Function Unit Specification in a Timed Multitasking Environment
Christo Angelov, Jesper Berthing, Krzysztof Sierszecki, Nicolae Marian · University of Southern Denmark Research Portal (University of Southern Denmark) · 2004
Abstract: The widespread use of embedded systems mandates the development of industrial software design methods, i.e. computer-aided design and engineering of embedded applications using formal models (frameworks) and standardized prefabricated components, following practices already established in mature areas of engineering such as mechanical engineering and electronics. For that purpose, a new system design framework (COMDES) has been recently developed. Under that framework, a distributed embedded application is specified in terms of subsystems (function units), such as sensor, control unit, actuator, operator station, etc, that interact by exchanging labeled messages (signals). Function units are conceived as software integrated circuits encapsulating one or more threads of control (activities) that are configured from prefabricated lowerlevel components (function blocks), such as basic and composite function blocks as well as reconfigurable function blocks of class state machine. The paper presents an enhanced specification of function units featuring time-triggered inputs and outputs, and the related lower-level components, such as activities and signal drivers, in the context of a new scheduling paradigm known as timed multitasking. This is a powerful yet elegant and simple technique, which can be used to eliminate task and transaction execution jitter in a dynamic scheduling environment. Timed multitasking has been extended to distributed transactions involving COMDES activities executed within distributed function units. To that end, a new type of kernel component has been developed –