Model-based development is state of the art in software engineering, due to its potential regarding automatic code synthesis. Nevertheless for embedded systems, where there exists a huge heterogeneity of used platforms, it is obvious that it is impossible to design a code generator that supports a priori all required platforms. Instead a code generator architecture is needed that is suited for an easy extensibility of the code generation ability. One possible solution is the use of template-based approaches. In this paper, we describe an approach 1 to develop safety-critical realtime systems by using openArchitectureWare, a modular MDA/MDD generator framework. We will present the tool-chain and discuss two lab applications.