ABSTRACT
Changes in the approaches taken to ensure reliability are refl ected in several international standards. The international standards of IEC 60300 series, established by the IEC TC56, are known as the standards for dependability management. This originally was a technical standard dealing with reliability of electronic components, but IEC 60300-1 (2003 edition), a core standard of the IEC 60300 series, did not fully include what was required for today’s software. The next edition is in progress, which will set standards for extended areas of products, systems, services, and processes as targets of dependability management. International safety standards ISO 13849-1 (EN954-1) and IEC 60204-1 (IEC 60204-1: 2009) can handle simple systems, subsystems, and parts, but are not sufficient to deal with systems that include software. Functional safety standard IEC 61508 was established in 2000 out of necessity for a safety standard for systems that include software. In IEC 61508, a system malfunction is divided into “random hardware failure” and “systematic failure”. The probability of random hardware failure is calculated by monitoring malfunctions due to the deterioration of parts; while systematic failures, caused by incorrect system design, development, production, maintenance, and operation, are kept from exceeding allowed target values through a verifi cation process such as the V-model and the documentation of all operations based on
the safety lifecycle. Systems are categorized according to mode of operation: low demand mode or high demand/continuous mode. The target failure limit for each mode is defi ned and managed as the Safety Integrity Level (SIL). The requirements of 4 stages from SIL1 to SIL4 (highest safety integrity) are also defi ned. With IEC 61508 as the base standard, machinery-related IEC 62061, process-related IEC 61511, nuclear-related IEC 61513, railway-related IEC 62278, etc. were established. For automotive systems, ISO 26262 was issued in 2011.
