Model-based software development is increasingly being used to develop software for electronic control units (ECUs). When developing safety-related software, compared to non-safety-related software development, additional requirements specified by relevant safety-standards have to be met. Meeting these requirements should also be considered to be best practices for non-safety-related software.This paper introduces a model-based reference workflow for the development of safety-related software conforming to relevant safety-standards such as IEC 61508 and ISO 26262. The reference workflow discusses requirements traceability aspects, software architecture considerations that help to support modular development and ease the verification of model parts and the code generated from those model parts, and the selection and enforcement of modeling and coding guidelines. Special focus is put on software unit and integration testing as an integral part of the overall verification and validation task. The presented methods and measures are mapped to the requirements of relevant functional safety-standards applied in the automotive industry.Furthermore the paper discusses the role of such a reference workflow for answering the ongoing question for software tool qualification. The new automotive safety-standard ISO 26262 introduces a new approach to adressing this topic. This approach is based on a new way of classifcation of the software tool based on the tools impact and the degree of confidence that a malfunction or erroneous output can be prevented or detected.