BS EN 61508-3:2002

BS EN 61508-3:2002:

• is intended to be utilised only after a thorough understanding of IEC 61508-1 and

  IEC 61508-2

• applies to any software forming part of a safety-related system or used to develop a safetyrelated system within the scope of IEC 61508-1 and IEC 61508-2. Such software is termed safety-related software

  - Safety-related software includes operating systems, system software, software in communication networks, human-computer interface functions, support tools and

  firmware as well as application programs.

  - Application programs include high level programs, low level programs and special purpose programs in limited variability languages (see 3.2.7 of IEC 61508-4).

• requires that the software safety functions and software safety integrity levels are specified.

  NOTE 1 – If this has already been done as part of the specification of the E/E/PE safety-related systems (see 7.2 of IEC 61508-2), then it does not have to be repeated in this part.

  NOTE 2 – Specifying the software safety functions and software safety integrity levels is an iterative procedure; see figures 2 and 6.

  NOTE 3 – See clause 5 and annex A of IEC 61508-1 for documentation structure. The documentation structure may take account of company procedures, and of the working practices of specific application sectors. 

• establishes requirements for safety lifecycle phases and activities which shall be applied during the design and development of the safety-related software (the software safety lifecycle model). These requirements include the application of measures and techniques, which are graded against the safety integrity level, for the avoidance of and control of faults and failures in the software.
• provides requirements for information relating to the software safety validation to be passed to the organisation carrying out the E/E/PES integration.
• provides requirements for the preparation of information and procedures concerning software needed by the user for the operation and maintenance of the E/E/PE safetyrelated system.
• provides requirements to be met by the organisation carrying out modifications to safetyrelated software.
• provides, in conjunction with IEC 61508-1 and IEC 61508-2, requirements for support tools such as development and design tools, language translators, testing and debugging tools, configuration management tools.