Modbus Exception: Illegal Data Address

What does 02 hex mean?

This Modbus exception occurs when the master device attempts to read from or write to a data address (register or coil) that is beyond the inverter's valid address range or does not exist. This indicates an incorrect memory address in the Modbus request, which the inverter cannot fulfill.

• The Modbus master is requesting an address that falls outside the inverter's valid Modbus register map (e.g., attempting to read register 9999 when max is 2000).
• Incorrect starting address or offset configured in the Modbus master for a block read/write operation.
• Inverter's Modbus address map differs from the master's configuration, leading to requests for non-existent addresses.
• Parameter (register) address may be dynamically hidden or unavailable depending on the inverter's operating mode or other parameter settings.
• Corrupted Modbus frame due to communication line noise, leading to the inverter misinterpreting the address.

Click steps to track your progress.

1. 1

   1. Refer to the inverter's Modbus communication manual for the complete and accurate Modbus register map and address ranges.

2. 2

   2. Verify the Modbus master's configuration (e.g., PLC program, HMI tags) to ensure all requested register addresses are within the inverter's valid range.

3. 3

   3. Use a Modbus sniffer tool to capture the Modbus request and identify the exact register address causing the exception.

4. 4

   4. Check if the requested register is accessible in the current inverter state; some parameters are only active in certain modes (e.g., stopped, RUN).

5. 5

   5. Ensure correct addressing convention (e.g., 0-based vs 1-based, 4xxxx vs 3xxxx for holding registers) is used consistently between master and slave.

6. 6

   6. Temporarily reduce the number of registers being read in a single Modbus transaction to rule out boundary issues.