In recent years, co-simulation and model exchange approaches have become ever more popular within the context of model-based design and analysis. This trend has led to the development of the Functional Mock-up Interface (FMI) specification—the de facto standard for model exchange and cosimulation— and a growing number of FMI-compliant tools. This paper addresses the FMI-based co-simulation of hybrid models representing closed-loop control systems, where a continuous time-based plant model is connected to a discrete event-driven controller model. The semantics of execution and data flow of such models are discussed and demonstrated with the help of a model that has been inspired by real-world applications. An example illustrates that popular proprietary simulation environments are not necessarily able to properly capture the semantics of these models. Furthermore, it is shown how existing concepts and tools can be successfully applied to implement such simulations properly.@en