Rockwell Automation 1756-SPESMNRMXT GuardLogix Controllers User Manual - Manuel (Page 92)

92 Rockwell Automation Publication 1756-UM020I-EN-P - August 2012
Chapter 6 Develop Safety Applications
Safety Programs Safety programs have all the attributes of standard programs, except that they can
only be scheduled in the safety task and can only contain safety components.
Safety programs can only contain safety routines, one of which must be
designated as the main routine, and one of which may be designated as the fault
routine.
Safety programs cannot contain standard routines or standard tags.
Safety Routines Safety routines have all the attributes of standard routines, except that they exist
only in a safety program. At this time, only ladder diagram is supported for safety
routines.
Safety Tags A tag is an area of a controller’s memory where data is stored. Tags are the basic
mechanism for allocating memory, referencing data from logic, and monitoring
data. Safety tags have all the attributes of standard tags with the addition of
mechanisms certified to provide SIL 3 data integrity.
When you create a tag, you assign the following properties:
• Name
• Description (optional)
• Tag type
• Data type
• Scope
• Class
• Style
• External Access
You can also specify if the tag value should be a constant.
TIP RSLogix 5000 software uses a watermark feature to visually distinguish a safety
routine from a standard routine.