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Unity Pro Network Troubleshooting

Modicon PAC Forum

A forum for topics related to the scope of Modicon PAC offers and ecosystem along the whole lifecycle: Modicon M580 and 340, EcoStruxure Control Expert, EcoStruxure Process Expert (Unity Pro) and more.


Unity Pro Network Troubleshooting

Hi. I am new in this Schneider world. I ve got Quantum PLC collecting data from 3rd party device via Quantum NOE network card using Modbus TCP/IP. IO Scanning is configure on the network card to receive data. The 3rd party device is showing live value on its local display but PLC is not able to read from 3rd party device. PLC can read values from other devices on the same network card. I can ping device from PLC network but PLC is cannot read data. How do I go about troubleshooting the link or data transmission. I there a feature on Unity Pro where u can monitor received data from network devices as well as checking status of all network devices? Something like NetPro.

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Re: Unity Pro Network Troubleshooting

The first item I would investigate is wat Modbus Function Code the 3rd party device supports. The I/O Scanner will initially attempt to use Function Code 23 Read / Write and if that fails with will them use Function Code 4 and 16 to process the Read and Write in the same message. The I/O Scanner will only Read and Write Modbus 4x Registers.

The 2nd item to check is the I/O Scanner Unit ID that is being used. The Modbus TCP/IP Products uses the Unit ID to direct the message through a bridge or gateway. The Unit ID is equivalent to the Modbus Address. Some devices will NOT respond to a Unit ID = 255. The valid range is 1 - 255.


The 3rd item to check is to make sure that the range of registers that you are requesting is valid and contains no gaps. Example, if you attempt to read Modbus Register 400001 thru 400010 range and the controller does not have Modbus Register 400005 it may reject the message instead of returning the data.


You can use Wireshark to capture the data packets and see what type of response you are getting to the Modbus TCP/IP queries. If you can provide specific on the 3rd part device (Manufacture and Device) it would assist in the troubleshooting.

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