48 Rockwell Automation Publication 1756-RM093J-EN-P - April 2018
Chapter 5 Characteristics of Safety Tags, the Safety Task, and Safety Programs
Tags classified as safety tags are either controller-scoped or program-scoped.
Controller-scoped safety tags can be read by either standard or safety logic or
other communication devices, but can only be written to by safety logic or
another GuardLogix safety controller. Program-scoped safety tags are accessible
only by local safety routines. These are routines that reside within the safety
program.
Tags associated with Safety I/O and produced or consumed safety data must be
controller-scoped safety tags.
Standard Tags in Safety Routines (tag mapping)
Controller-scoped standard tags can be mapped into safety tags, providing you
with a mechanism to synchronize standard and safety actions.
Any controller-scoped safety tag is readable by any standard routine, but
the update rate is based on the execution of the safety task. This means
that safety tags are updated at the safety task periodic rate, which is
different from standard tag behavior.
ATTENTION: When using standard data in a safety routine, you are responsible
for providing a reliable means of ensuring that the data is used in an appropriate
manner. Using standard data in a safety tag does not make it safety data. You
must not directly control a safety output with standard tag data.
This example illustrates how to qualify the standard data with safety data.
Figure 14 - Qualify Standard Data with Safety Data
ONS
MappedBooleanTag LatchOneShot
Node30ComboModule:O.Pt03Data
Node30ComboModule:I.Pt07Data Node30ComboModule:O.Pt03Data
Latch circuit to prevent automatic restart if the standard input
(MappedTag) is failed in a ‘stuck at 1’ state.
Safety Input Qualifier for Mapped Tag
Safety Output
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