The development process of electronic control units (ECU) is increasingly supported by different tools. The target-specific code-generation for single micro-controllers becomes a standard technology. Thus a continuous tool support during the whole development cycle is possible. This extends from the specification of the functionality to the implementation of the software on the controller. The next generation of tool support is not only focused on single micro-controllers it also supports the design of systems consisting of different controllers connected via various communication entities. Thus the goal of the tool support is the automatic code-generation for such distributed embedded real-time systems including support of different communication buses (e.g., Controller Area Network CAN, Time Triggered Protocol TTP) and different processor targets. The additional aspects resulting from the distribution of functionality on different hardware requires support in the following domains: modeling of a hardware architecture, mapping of the software elements on hardware elements, time analysis, feasibility check of the architecture and code generation.This paper describes the whole development process using the tools Cierto VCC and ASCET. The emphasis is placed on the coupling of both tools via automatic C-code generation.