40 Rockwell Automation Publication 5094-UM001E-EN-P - April 2020
Chapter 1 Digital I/O Module Operation in a Logix 5000 Control System
Safety Application Requirements
Safety application requirements include evaluating the following:
•Probability of failure rates (PFD and PFH)
• System reaction time settings
• Functional verification tests that fulfill appropriate safety-level criteria
Creating, recording, and verifying the safety signature is also a required part of 
the safety application development process. The safety controller creates the 
safety signatures. The safety signature consists of an identification number, date, 
and time that uniquely identifies the safety portion of a project. This number 
includes all safety logic, data, and safety I/O configuration.
For safety system requirements, including information on the safety network 
number (SNN), verifying the safety signature, functional verification test 
intervals, system reaction time, and PFD/PFH calculations, see the 
GuardLogix 5580 and Compact GuardLogix 5380 Controller Systems Safety 
Reference Manual, publication 1756-RM012
.
You must read, understand, and fulfill the requirements that are described in this 
publication before you operate a safety system that uses FLEX 5000 I/O safety 
modules.