The design space that a system architect should manage when designing a microcontroller for a safety related system is rather large due to the variety of faults that can affect the given Equipment Under Control (EUC), the different failures that these faults can generate and the wide set of techniques that can be used to detect, confine or stop the resulting hazards, each one with its efficiency and cost. In this paper it is proposed a systematic platform-based approach, in which a library of blocks (HW and SW) is used together with a set of tools and methodologies to find the optimum solution in this design space, following the IEC61508 guidelines.