Rockwell Automation Logix5000 Controllers Controller Information and Status Programming Manual - Manual (Page 13)

Connections Chapter 1
Configure a major fault to occur
You can configure modules to generate a major fault in the controller if they lose
their connection with the controller. This interrupts the execution of logic and
runs the Controller Fault Handler. If the Controller Fault Handler does not clear
the fault, the controller shuts down.
When you select Major Fault On Controller…Run Mode, the controller:
• Must be connected to the module during the Program transition to Run
mode. During the Program to Run mode transition, there can be a 20-
second delay.
During this delay, the controller makes one attempt to connect to a module.
If you select Major Fault On Controller…Run Mode and you cannot
connect during the 20-second delay, a fault occurs because at least one
required connection is not established before going to Run mode. This is a
3/23 type fault code. This fault can occur in large systems with networked
I/O.
• Registers a fault if the connection is dropped while in Run mode. A required
I/O module connection failed, creating a 3/16 type fault.
For fault codes, see the Logix5000 Controllers Major and Minor Faults
Programming Manual , publication 1756-PM014 .
Monitor the health of a module
If you do not configure the major fault to occur, you should monitor the module
status. If a module loses its connection to the controller, outputs go to their
configured faulted state. The controller and other I/O modules continue to
operate based on old data from the module.
Rockwell Automation Publication 1756-PM015F-EN-P – October 2014 13