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PLC COmmunication

We purchased some equipment that has a DL06 PLC in it.  I need to communicate with it using RTU MODBUS.  I am completely new to MODBUS communication.  I can connect to my equipment but any command I send it either results in a timeout error or executes error-free but does not actually do anything at the PLC level.  In the code below I am simply trying to turn on 2 switches out of a bank of 4.  I assume I need the master to write the command and the slave to read it.  I get a timeout error when I run the VI.  Thanks for any help anyone can offer.

 

MODBUS.jpg

 

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What option of MODBUS are you using? Currently, NI provides four options for MODBUS connectivity that you can find here: https://forums.ni.com/t5/NI-Labs-Toolkits/LabVIEW-Modbus-API/ta-p/3524019

 

The reason why I ask is because if you're using the free NI Modbus library or the NI Labs MODBUS API, keep in mind those two options are unsupported and you may find faster help at the dedicated discussion forums: https://forums.ni.com/t5/NI-Labs-Discussions/NI-LabVIEW-Modbus-API-Discussion/td-p/3373078

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