Formal methods are making their way into the development of safety-critical systems. In this paper, we describe a case study where a simple 2oo3 voting scheme for a shutdown system was verified using two bounded model checking tools, CBMC and EBMC. The system represents Systematic Capability level 3 according to IEC 61508 ed2.0. The verification process was based on requirements and pseudo code...

For the development of Application Specific Integrated Circuits (ASICs) for safety-related applications Hardware Description Languages (HDLs) are used. The process of such development is presented in the international standard IEC 61508, which introduces guidelines and calculations to achieve a specific Safety Integrity Level (SIL). However, it is not concerning the estimation and calculation o...

The 2 out of 4-system (2oo4) is an advanced safety architecture. A 2oo4-system is 2-failure safe, this means that at least two of the four channels have to work correctly in order to trigger the safety function. In order to classify the quality of a system different parameters have to be calculated, like the PFD and MTTF. In this paper, equations are indicated for PFD for normal and common-caus...

Functional safety standards (ISO 26262, IEC 61508) require a safety life cycle which demands additional design and engineering tasks to be managed. This paper addresses how the existing FMEAs have to be extended and refocused to address and overview signal paths throughout the system. The safety standards require to classify signals with a SIL (Safety Integrity Level) and the higher the SIL the...

With the advent of comprehensive safety standards for software intensive safety related systems, such as IEC 61508 and its speciali-sations for particular industry sectors (medical, machinery, process, etc), there is a need to establish combinations of techniques which can be used by industry to demonstrate conformance to these standards for particular developments. In this paper we describe on...

Many software development practices aim at ensuring that software is correct, or fault-free. In safety critical applications, requirements are in terms of probabilities of certain behaviours, e.g. as associated to the Safety Integrity Levels of IEC 61508. The two forms of reasoning – about evidence of correctness and about probabilities of certain failures – are rarely brought together explicit...

Formal methods have been successfully used to establish assurances for safety-critical systems with mathematical rigour. Based on our experience in developing a methodology and corresponding tools for a change management for formal methods, we have generalised this approach to a comprehensive methodology to maintain heterogeneous document collections consisting of both formal and informal docum...

Um Software verantwortungsbewusst in den Markt zu bringen, muss sie ebenso wie andere Produkte dem Stand der Technik entsprechen. Das zwingt zur Arbeit mit Normen, z.B. der IEC 61508 oder ISO 26262, denn sie repräsentieren diesen Stand der Technik, insbesondere für sicherheitsgerichtete Software. Den Normen gerecht zu werden bedeutet, die für eine Arbeit zutreffenden Normenanforderungen zu iden...

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