—The development of real-time embedded systems is quite complex because of the wide range of execution platforms and of the importance of non-functional requirements. Further-more, Model Driven Engineering is particularly suitable for han-dling the diversity of implementation targets. Therefore, several real-time embedded systems development suites leverage Model Driven Engineering by automatically generating platform-specific code from high-level design models. Such tools may also take non-functional requirements into account by integrating verification activities. These activities typically rely on the generation of formal models from the same high-level design descriptions used for code generation. However, few tool suites support both code and formal model generation. Furthermore, among these, most overlook real-time operating systems mechanisms. Therefore, both code and formal models generated by these tool suites may not behave as specified in the high-level design descriptions. The present work extends the SExPIsTools code generator tool suite with a support for the generation of formal models. The proposed strategy relies on the composition of formal model fragments described using an extension of the classical Time Petri Nets. This paper presents a formalization of this composition that generically considers the behavior of platforms. As an illustration, we then give the formal model describing the behavior of an application on two different platforms (OSEK/VDX and VxWorks) and check a safety property on both models.