Modbus error: Illegal data address

26 Aug 2025
Knowledge

Problem

When using Cloud Logging or Cloud Notify with Modbus TCP, testing the variables by pressing Run test returns the error: illegal data address.

Cause

At least one of the addresses in the error message does not exist in the PLC.

Solution

Remove any variables from the IXON Cloud that do not exist in the PLC.

If this is already the case, try setting Read mode to Optimized in the Fleet Manager > Devices > Your device > Your data source.

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Modbus error: Illegal data address

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Modbus-error-Illegal-data-address

Modbus error: Illegal data address

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Modbus error: Illegal data address

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