Document: NUREG-0800
Document ID: 4f141c71-35ca-4353-9047-a13efe6d56b7
Document Type: srp
Title: Revision 6 - August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A308.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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CFR Title: 

Content:
behavior, or (3) software behavior is fully specified. Of particular concern is the behavior of the software in the presence of unexpectedly high or low rates of message traffic. Safety means 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 RG 1.152. Security means the establishment of SDOE per RG 1.152. Timing means that functions that must operate within specific timing constraints are identified, and that timing criteria are 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. SRP BTP 7-21, “Guidance on Digital Computer Real-Time Performance,” provides additional guidance on real-time performance. B.3.3.1.2 Process Characteristics of SRS Software development process characteristics exhibited by the SRS should include completeness, consistency, correctness, style, traceability, unambiguity and verifiability. Completeness means that all actions required of the computer system are fully described for all operating modes and all possible values of input variables (for example, the complete span of instrument inputs or clock/calendar time).* The SRS should describe any actions that the software is prohibited from executing. The operational environment within which the software will operate should be described. All variables in the physical environment that the software *Implementation of safety functions should not rely upon a date (calendar time). Actions depending upon calendar time should