Document: NUREG-0800
Document ID: be3ce44f-6784-4f40-baef-12c96ec1ff96
Document Type: srp
Title: provides additional guidance on digital data communications systems.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070670183.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.9
CFR Part: 
CFR Title: 

Content:
s means that the design is such that the software will operate correctly in the presence of unexpected, incorrect, anomalous and improper (1) input, (2) hardware behavior, or (3) software behavior. In particular, the software should not fail, and should not provide incorrect outputs, in the presence of these conditions. Attention should be paid to those values of input variables that are physically possible to the device, even if logically impossible in the application (to account for sensor errors, communication line noise, and similar concerns). Safety means that the detailed design introduces no new safety hazards into the safety system. Security means that unauthorized changes are prevented, detected, or mitigated as appropriate. Regulatory Guide 1.152, Revision 2, Section C.2.3, “Design Phase,” contains guidance on security requirements to be addressed during the design phase. BTP 7.14-58 Revision 5 - March 2007 Timing means that the time delay between stimulus and response is deterministic. SRP BTP 7-21 provides additional guidance on real-time performance. B.3.3.3.2 Process Characteristics of SDS The SDS should exhibit each of the following software development process characteristics: completeness, consistency, correctness, style, traceability, and verifiability. Completeness means that the detailed design specifies the actions of each software unit for the entire domain of each input variable (for example, the complete span of instrument inputs or clock/calendar time). The design should be sufficiently complete to permit implementation to take place. Actions should be specified for all situations anticipated in the SRS. Equipment, human, hardware, and software interfaces should be correctly and fully specified. Equations, algorithms, and control logic should be correctly and fully specified. Consistency means that the detailed design is consistent with the architectural design, and that the detailed design elements are mutually consistent. Design