Modicon 984 Model 685 Modbus Plus Address


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Hello folks,

I am working on testing some network issues on a PLC network developed in the early 90s. It is a Modicon Modbus/Modbus Plus network.

We have a Modicon 984 Series 685 PLC with one Modbus Port and one Modbus Plus port. This PLC has two sets of DIP switches - One set of 8 switches on the top of the PLC and one set of 7 switches on the bottom of the PLC.

I have not been able to find an explanation of how these DIP switches work. Most of the resources online only talk about the 685E controller which has only one bank of 8 DIP switches on the bottom.

Does anyone here have any experience with this? My goal is simply to set the Modbus Plus address of the controller.

Any help on this would be greatly appreciated!