Rockwell Automation Publication 1756-UM058G-EN-P - November 2012 213
Appendix C
Use Ladder Logic To Perform
Run Time Services and Reconfiguration
You can use ladder logic to perform run-time services on your module. For
example, page 59
shows how to reset an electronic fuse module by using
RSLogix 5000 software. This appendix provides an example of how to reset the
same fuse without using RSLogix 5000 software.
In addition to performing run time services, you can use ladder logic to change
configuration. Chapter
7 explained how to use the RSLogix 5000 software to set
configuration parameters in your ControlLogix digital I/O module. Some of
those parameters may also be changed through ladder logic.
Using Message Instructions
In ladder logic, you can use Message instructions to send occasional services to
any ControlLogix I/O module. Message instructions send an explicit service to
the module, causing specific behavior to occur. For example, unlatching a high
alarm can be performed by a message instruction.
Message instructions maintain the following characteristics:
• Messages use unscheduled portions of system communication bandwidth
• One service is performed per instruction
• Performing module services does not impede module functionality, such
as sampling inputs or applying new outputs
Topic Page
Using Message Instructions 213
Processing Real-time Control and Module Services 214
One Service Performed Per Instruction 214
Create a New Tag 214
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