Résumé : This paper presents a model and its semantics for the design of embedded systems that contain data-intensive parts such as multimedia applications, and require adaptivity w.r.t. criteria such as platform resources or quality of service (QoS). The proposed solution relies on a combination of: i) the repetitive model of computation dedicated to the design of high-performance embedded systems and ii) reactive control features based on finite state machines and modes. It is defined within a framework, called Gaspard, that implements automatic transformations that lead to various target languages, e.g., synchronous languages, SystemC, VHDL. The new model offers the adequate expressive power to describe complex behaviors of high-performance embedded systems. It also reconciles execution models dedicated to regular computations and control-oriented models that rather lead to irregular computations.