Invalid Modbus Address

What does 2 mean?

The Modbus request attempted to access a bit or word address that does not exist in the slave device's memory map. This means the master is querying or writing to an unsupported register location. Continuous invalid address attempts will lead to communication errors and prevent proper data exchange or control.

• Modbus master device is attempting to read from or write to a register address that is not implemented in the soft starter's Modbus map.
• Incorrect register mapping in the Modbus master's configuration (e.g., offset error, wrong register block definition).
• Different Modbus register addressing convention used by master and slave (e.g., 0-based vs. 1-based addressing).
• Slave device (soft starter) has a restricted or limited Modbus memory map compared to what the master expects.
• Firmware update on the soft starter changing the Modbus register map without corresponding update to the master device's configuration.

Click steps to track your progress.

1. 1

   1. Refer to the soft starter's Modbus communication manual for the exact and supported Modbus register addresses.

2. 2

   2. Cross-reference the register addresses configured in the Modbus master's program (PLC, HMI) with the soft starter's documentation.

3. 3

   3. Verify the addressing convention (e.g., offset of 40001 for holding registers, 30001 for input registers) is correctly applied in the master.

4. 4

   4. Use a Modbus sniffer to capture the Modbus requests and identify the specific invalid register address being targeted.

5. 5

   5. Test by reading a known, commonly supported register address (e.g., motor current or status word) to confirm basic communication.