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:
quirements for on-line in-service testing and diagnostics should be provided. Robustness requires that the behavior of the software in the presence of unexpected, incorrect, anomalous and improper (1) input, (2) hardware behavior, or (3) software behavior be fully specified. Of particular *Implementation of safety functions should not rely upon a date (calendar time). Actions depending upon calendar time should account for concerns such as those identified with the year 2000 (two-digit 00). Rev. 4 — June 1997 Appendix 7-A BTP HICB-14-30 concern is the behavior of the software in the presence of unexpectedly high or low rates of message traffic. Safety requires that the software functions, operating procedures, input, and output be classified according to their importance to safety. Requirements important to safety should be identified as such in the SRS. The identification of safety items should include safety analysis report requirements, as well as abnormal conditions and events as described in Reg. Guide 1.152. Security requires that security threats to the computer system be identified and classified according to severity and likelihood. Actions required of the software to detect, prevent, or mitigate such security threats should be specified, including access control restrictions. Timing requires that functions that must operate within specific timing constraints be identified, and that timing criteria be specified for each. Timing criteria should be provided for each mode of operation. Timing requirements should distinguish between goals and requirements. Timing requirements should be stated in such a way that the time delay between stimulus and response for safety actions is deterministic under normal and anticipated failure conditions. BTP HICB-21 provides additional guidance on real-time performance. Software Development Process Characteristics Software development process characteristics exhibited by the SRS should include completeness, consistency,