1.1 General This International Standard is applicable to NPP computer-system hardware for systems of Class 1 and 2 (as defined by IEC61513 ). The structure of this standard has not changed significantly from the original 1989 issue; however, some issues are now covered by standards which have been issued in the interim (for example, IEC61513 for system architecture design) and references to new standards have been provided where applicable. The text of the standard has also been modified to reflect developments in computer system hardware design, the use of pre-developed (for example, COTS) hardware and changes in terminology. Computer hardware facilities used for software loading and checking are not considered to form an intrinsic part of a system important to safety and, as such, are outside the scope of this standard. NOTE1 Class 3 computer-system hardware is not addressed by this standard, and it is recommended that such systems should be developed to commercial grade standards. NOTE2 In 2006 the development of a new standard to address hardware requirements for “very complex?? hardware was discussed within IECSC45A . If such a standard is developed then that standard would be used for the development of “very complex?? hardware in preference to IEC60987 . 1.2 Use of this standard for pre‑developed (for example, COTS) hardware assessment Although the primary aim of this standard is to address aspects of new hardware development, the processes defined within this standard may also be used to guide the assessment and use of pre-developed hardware, such as COTS hardware. Guidance has been provided in the text concerning the interpretation of the requirements of this standard when used for the assessment of such components. In particular, the quality assurance requirements of 4.3, concerning configuration control, apply. Pre-developed components may contain firmware (as defined in 3.8), and, where firmware software is deeply imbedded, and effectively “transparent?? to the user, then IEC60987 should be used to guide the assessment process for such components. An example of where this approach is considered appropriate is in the assessment of modern processors which contain a microcode. Such a code is generally an integral part of the “hardware??, and it is therefore appropriate for the processor (including the microcode) to be assessed as an integrated hardware component using this standard. Software which is not firmware, as described above, should be developed or assessed according to the requirements of the relevant software standard (for example, IEC60880 for Class 1 systems and IEC62138 for Class 2 systems). 1.3 Applicability of this standard to programmable logic devices development I&C components may include programmable logic devices that are given their specific application logic design by the designer of the I&C component, as opposed to the chip manufacturer. Examples of such devices include complex programmable logic devices (CPLD) and field programmable gate arrays (FPGA). While the programmable nature of these devices gives the development processes used for these devices, some of the characteristics of a software development process and the design processes used for such devices, are very similar to those used to design logic circuits implemented with discrete gates and integrated circuit packages. Therefore, the design processes and design verification applied to programmable logic devices should comply with the relevant requirements of this standard (i.e. taking into account the particular features of the design processes of such devices). To the extent that software-based tools are used to support the design processes for programmable logic devices, those software tools should generally follow the guidance provided for software-based development tools in the appropriate software standard, i.e. IEC60880 (Class 1 systems) or IEC62138 (Class 2 systems).