Hi everyone,

I’m trying to read data from a Janitza UMG96-PA power meter via Modbus TCP using the built-in MB_CLIENT function block in TIA Portal (V18). The PLC is a CPU 1515F-2 PN.

I’ve gone through the documentation, and from what I can tell my settings are correct. I’ve attached screenshots of both my hardware configuration and the MB_CLIENT setup (Image 1 and 2).

However, when I go online, MB_CLIENT keeps returning the error status 8384. According to the help file, this is described only as a “data value error” (Image 3), but there’s no detail on what causes it.

To verify the device, I tested the same registers using ModScan and Modbus Poll, and both tools can read the data successfully using the settings shown in Image 4.
 

Has anyone encountered error 8384 before?
What does this “data value error” actually refer to?
Any hints or things I might be missing when communicating with a Janitza meter?

MB_Client function block

MB_Client input and output datablock

MB_Client input MB_data_PTR

Hello,

Some of the screenshots are too small. You can't see anything.

Status 8384 indicates that an invalid exception code was received.

In this case, please check whether the server expects a specific ID. If necessary, adjust the MB_UNIT_ID in the instance data block MB_Client.

What is the function of the "MB_UNIT_ID" in the instance data block of the Modbus block "MB_CLIENT"?

Best regards