This paper describes a simulation technique for Real-Time Hw/Sw systems based on an object executable model. It allows designers to seamlessly estimate and verify their solutions from a high-level functional description to a Hw/Sw partitioned design. The same model, enhanced with algorithms, can be used to simulate interpreted models in order to observe the behavior of a whole system and its environment, as well as uninterpreted models which are useful for performance estimation and so to help Hw/Sw partitioning. Our (co-)simulation technique is based on the translation of a high level model of the application into a C++ program which uses a library of predefined classes. While running, the program produces an event trace which contents can be set by the user. This technique allows to quickly analyze the influence of application or architecture parameters on the application behavior.