Rockwell Automation Publication 1756-RM012B-EN-P - April 2018 97
Appendix F
Studio 5000 Logix Designer Application,
Version 31 or Later, Safety-application
Instructions
De-energize to Trip System
All safety input values that are associated with a particular connection are set to
safe state when a CIP Safety connection fault condition is detected. When
using diverse input pairs, one of the inputs uses a value of one to initiate the
safety function. This requires safety logic that evaluates fault conditions, so
that the safety function is executed when an input fault occurs (even though
the input value remains at zero).
Use Connection Status Data
to Initiate a Fault
Programmatically
The following diagrams provide examples of the application logic that is
required to latch and reset I/O failures. The examples show the logic necessary
for input only modules, and for input and output combination modules. The
examples use the Combined Status feature of the I/O modules, which presents
the status of all input channels in one Boolean variable. Another Boolean
variable represents the status of all output channels. This approach reduces the
amount of I/O conditioning logic that is required and forces the logic to shut
down all input or output channels on the affected module.
Use the Input Fault Latch and Reset Flowchart on page 98
to determine which
rungs of logic are required for different application situations. Ladder Diagram
Example 1 on page 99 shows logic that overwrites the actual input-tag variables
while a fault condition exists. If the actual input state is required for
troubleshooting while the input failure is latched, use the logic shown in
Ladder Diagram Example 2 on page 100
. This logic uses internal tags that
represent the inputs to be used in the application logic. While the input failure
is latched, the internal tags are set to their safe state. While the input failure is
not latched, the actual input values are copied to the internal tags.
Use the Output Fault Latch and Reset Flowchart on page 101
to determine
which rungs of application logic in Ladder Diagram Example 3 on page 101
are
required.
Topic Page
De-energize to Trip System 97
Use Connection Status Data to Initiate a Fault Programmatically 97
IMPORTANT We recommend use of general safety-application instructions (Table 5 on
page 69) rather than the instructions detailed in this appendix.
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