A safety signature verifies the integrity of a safety application:
The safety signature applies to the entire safety portion of the controller project. The ability to create, record, and verify the safety signature is a mandatory part of the safety-application development process. The safety signature must be present to operate as a SIL 2/PLd or SIL 3/PLe safety controller. Nothing in the standard application is included in the safety signature.
The safety signature is a hierarchy of multiple safety signature elements. For example, the safety task, programs, and routines are examples of safety signature elements. Safety signature elements can help you during impact analysis by identifying the individual changes within a controller project. If your validation plan does not require revalidation of unchanged elements, your certification effort can be reduced.
All safety signature elements are created at the time that you generate the safety signature for the project. To view all safety signature elements for a project, you can run the Safety Signature report.
The safety signature and each of its elements have the following:
Time stamp—The date and time that the safety signature was generated. For a safety signature element, the time stamp changes whenever its signature ID changes. The time stamp is based on the local clock of the computer that generated the signature.
