Rockwell Automation Allen-Bradley POINT Guard - Message Instructions

Rockwell Automation Publication 1734-UM013J-EN-P - July 2014 155
Appendix B
Get I/O Diagnostic Status from Modules in Logix
Systems
You can use message instructions in a Logix system to determine the cause of
input point or output point faults.
Message Instructions
When the controller detects a fault on an input or output point, you can use a
message instruction to explicitly retrieve the cause of the fault.
In this example, we use a 1734-OB8S module with the Input Status set to return
Point Status. This table illustrates the controller tags that you can monitor for
this module.
Use the Point Output Status bits to detect if one or more of the output points on
the module have a fault:
• If any status bit goes to a value of 0 (0 = error, 1 = no error), use the status
bit to condition your message instruction as follows.
• Place these rungs in the standard task.
Topic Page
Message Instructions 155
Configure the Message Instruction 156
Class, Instance, and Attribute Data for I/O Modules 157