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Why can I not connect to my PLC over Modbus Serial?

Published date: 30 May 2019

Issue
Connecting over Modbus Serial

Product Line
Modicon

Enviroment
Modbus Serial

Cause
RSLinx conflict

Resolution
If you cannot connect to your PLC over Modbus Serial you may have Rockwell Drivers/RSLinx installed on your PC. The Rockwell software takes full control of the COM port and will not allow anything else to communicate out. The Rockwell software needs to be completely shut down to free up the COM port. 

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