Document: NUREG-0800
Document ID: c90016c6-e03f-4224-8ff3-87a6f7d3ca42
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500547.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
ced. The SAD should include all of the functional and software development process characteristics listed below. Functional Characteristics For each of the functional characteristics, the requirements imposed on the software for that characteristic should be satisfied by the software architecture. A review of the software architecture requires a concurrent review of the hardware architecture. Functional characteristics addressed by the SAD should include reliability, safety, security, and timing. Reliability requires that the combined hardware and software architecture be such that individual software element failure will not compromise safety. The software architecture should identify actions to be taken in the event of error detection. The hardware and software architecture should be reviewed to verify that the propagation of errors is controlled via a well-structured modular design. Safety requires that the software architecture introduce no new hazards into the safety system. The safety functions should be separated from normal operating and overhead functions, with well-defined and strictly controlled interfaces between them. Any online maintenance features should be included. The hardware and software architecture should be reviewed to verify that there is no violation of other criteria such as single failure, channel separation, and separation between Class 1E and non-1E systems. The review should verify that no new hazards are introduced into the safety system as a result of the architecture configuration. Security requires that the architecture correctly handle identified security threats, and introduce no new security threats. Rev. 4 — June 1997 Appendix 7-A BTP HICB-14-32 Timing requires that the architectural design describe all timing limitations, the strategy for handling each, the required margins, and the method of measuring those margins. A timing specification should exist for each architectural element, in terms of minimum and maximum times for