Application software design and development

1 The first objective of the requirements of this clause is to create an application software architecture that is consistent with the hardware architecture and that fulfils the specified requirements for software safety (see 12.2). 

2 The second objective of the requirements of this clause is to review and evaluate the requirements placed on the software by the hardware and embedded software architecture of the SIS. These include side-effects of the SIS hardware/software behaviour, the application specific configuration of SIS hardware, the inherent fault tolerance of the SIS and the interaction of the SIS hardware and embedded software architecture with the application software for safety. 

There are a number of approaches to providing safe application software in SISs. However, regardless of the approach used to achieve safe application software, it is assumed that the safety life cycle steps prior to application software development have been executed properly (for example, hazard and risk assessment, functional description development, equipment (hardware and software) selection). 

Following is a list of items to consider when developing application software for SISs. 

No reproduction or networking permitted without license from IHS 

The application software documentation will be used to determine the suitability of the application software to each SIF SIL. An independent analysis should be made to determine that the application software meets the SIL. 

2 With regard to guidance on selection of application software design methods and techniques, systems with a safety requirement up to SIL 3 should be designed in accordance with the instructions given in the supplier s safety manual as part of a system conforming with lEC 61508. For SIL 4 systems, the developer should additionally confirm that the selected methods do conform with the requirements of lEC 61508-3. 

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Application software design and development Architecture To create a software architecture that fulfils the specified requirements for software safety To review and evaluate the requirements placed on the software by the hardware architecture of the SIS 12.4.3 SIS application software safety requirements specification SIS hardware architecture design manuals Description of the architecture design, for example, segregation of application S/W into related process subsystem and SIL(s), for example, recognition of common application S/W modules such as pump or valve sequences... 

Application software design, and development. Support tools and programming languages To identify a suitable set of configuration, library, management, and simulation and test tools, over the whole safety life cycle of the software (utility software) 12.4.4 SIS application software safety requirements specification Description of the architecture design Manuals of the SIS List of procedures for use of utility software Verification information... 

Application software design and development To create software architecture, this fulfils the software safety requirements as well as the requirements placed by hardware architecture. 12.4.3... 

Application software design and development Support tool and programming language Configuration, library, and management simulation and test tool necessary for software safety life cycle. Also procedure for program development of application software. 12.4.4... 

Application software design and development Application module development and implementation of application software to fulfill application safety. 12.4.5... 

Depending on applicability, various requirements discussed in Clauses 2.1.4 and 2.2.4 will be valid here. The foregoing bullet points specify the objective, whereas those listed next are applicable for various requirements for software design and development ... 

The procedures used to design and develop project-specific application software, including version control and management, the documentation provided, and backup copy availability. 

In many instances operating system software has already been developed and is offered as a fundamental part of the computer system ready for application software to be developed or configured. In such cases it is prudent to establish the existence of the respective software quality assurance plans and procedures and the design, development, and testing records. Identification and examination of this documentation can be conducted and recorded as part of the supplier audit. (See Sec. VI.)... 

During the design and development of computer systems or application software to be used as components in medical devices, to be manufactured and/or sold in the USA, consideration must be given to meeting the requirements for design in 21 CFR Part 820 of the FDA regulations. 

Many examples of inventory management software and systems exist with capabilities to translate across different part identification numbers and actively track inventories. The Army should not have to engage in basic design and development of software. Conversely, not all existing applications are appropriate or effective for this particular situ-... 

In general, in order to ensure testability, it is recommended that the application software integration test specifications are considered during the design and development phase. 

One aspect of comparison is not mentioned the amoimt of precise design and development suggestions to achieve a safe system. Such precise suggestions can be related to the system (safety) design, e.g. software or hardware redimdancy and failure tolerance, as well as techniques and measures. We think that precise recommendations are very important for the application of a standard concerning safety-critical systems. 

NOTE 2 lEC 61511-2 ANSI/ISA-84.00.01-2004 Part 2 flEC 61511-2 Modf provides guidance on how to design and develop the application software when SIF of different SIL are to be implemented in the SIS. 

This promotes the basic requirements for design and development of E/E/PE systems including hardware and software architecture, sensor, actuators, and PE including embedded software, application specific integrated circuit (ASIC), etc. Major issues related to this shall include but not be limited to the following ... 

It is concluded that it would be reasonable to claim that available systems and application software design techniques were suitable for safety related applications. The limiting factors are perhaps the lack of an integrated development environment extending to formal methods and the poor support for testing. The provisos are less significant when PLCs are used in simple plications. 

The embedded operating system we use for our experiments has been designed and developed according to the ARINC 653 avionics standard Avionics Application Software Standard Interface). The ARINC 653 is a standard interface for time and space partitioning of embedded systems resources. It is compliant with the IMA Integrated Modular Avionics) trend. The main objective of IMA is to simplify the integration of avionics software, by proposing the use of... 

Software quality assurance methods are deployed throughout the development and testing of both operating system and application software development. Software development takes place under safety life cycle procedures as specified in lEC 61508 part 3. The software design and testing is fully documented so that third-party inspectors can understand PLC operation. 

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