IEC 61508 Functional Safety Assessment Rosemount Inc. - Exida

5.1.2 Safety Requirements Specification and Architecture DesignAs defined in [D17] a safety requirements specification (SRS) is created for all products that mustmeet IEC 61508 requirements. For the 3051 C/T/L Pressure Transmitter, the requirementsspecification [D30] contains a system overview, safety assumptions, and safety requirementssections. During the assessment, exida certification reviewed the content of the specification forcompleteness per the requirements of IEC 61508.Requirements are tracked throughout the development process by the creation of a series oftraceability matrices which are included in the following documents: [D30], [D35], [D73], and[D127]. The system requirements are broken down into derived hardware and softwarerequirements which include specific safety requirements. Traceability matrices show how thesystem safety requirements map to the hardware and software requirements, to hardware andsoftware architecture, to software and hardware detailed design, and to validation tests.Requirements from IEC 61508-2, Table B.1 that have been met by Rosemount, Inc. include projectmanagement, documentation, structured specification, inspection of the specification, andchecklists.Requirements from IEC 61508-3, Table A.1 that have been met by Rosemount, Inc. includeBackward traceability between the safety requirements and the perceived safety needs.[D80a] documents more details on how each of these requirements has been met. This meets therequirements of SIL 3.5.1.3 Hardware DesignHardware design, including both electrical and mechanical design, is done according to [D17]. Thehardware design process includes creating a hardware architecture specification, a peer review ofthis specification, creating a detailed design, a peer review of the detailed design, componentselection, detailed drawings and schematics, a Failure Modes, Effects and Diagnostic Analysis(FMEDA), electrical unit testing, fault injection testing, and hardware verification tests.Requirements from IEC 61508-2, Table B.2 that have been met by Rosemount, Inc. includeobservance of guidelines and standards, project management, documentation, structured design,modularization, use of well-tried components, checklists, semi-formal methods, computer aideddesign tools, simulation, and inspection of the specification. This is also documented in [D80a]. Thismeets the requirements of SIL 3.5.1.4 Software (Firmware) DesignSoftware (firmware) design is done according to [D17]. The software design process includessoftware architecture design and peer review, detailed design and peer review, critical codereviews, static source code analysis and unit test.Requirements from IEC 61508-3, Table A.2 that have been met by Rosemount, Inc. include faultdetection, error detecting codes, failure assertion programming, diverse monitor techniques,stateless software design, retry fault recovery mechanisms, graceful degradation, forward andbackward traceability between the software safety requirements specification and softwarearchitecture, semi-formal methods, event-driven, with guaranteed maximum response time, staticresource allocation, and static synchronization of access to shared resources.© exida Certification rosemount 11-07-062 r007 v1 r1 iec 61508 assessment.docx, 3/8/2012Michael Medoff Page 15 of 21