Issue
Understanding common Modbus error codes that appear in Building Operation trace logs.
Product Line
EcoStruxure Building Operation
Environment
- Building Operation Automation Server
- Building Operation Enterprise Server
- Modbus
Cause
Modbus protocol errors are seen when looking at Building operation trace logs.
Resolution
Below are common Modbus error codes observed in trace logs, their meanings, and example log entries.
Error Code 4 – Server Device Failure
Message: RESP_DATA_MISMATCH
Meaning:
This error indicates that the Modbus slave device encountered an unrecoverable internal error while attempting to execute the requested command. This is a problem within the slave device itself, not a communication error on the client side.
Possible Causes:
- Attempting to write to a protected memory area
- Device in an unsuitable state for the command
Example Log Entry:
Dec 27 08:15:01 AS-P-18E4A6 nsp_servers[1151]: 2024-12-27 08:15:01.767 [1654641088] nsp.pin.modbus.SerTransport Flush buffer. Protocol error code = 4Error Code 10 – Illegal Data Value
Message: Flush buffer. Protocol error code = 10
Meaning:
This error suggests the slave device rejected a data value sent by the master.
Possible Causes:
- Value out of acceptable range
- Attempt to write to a read-only address
Example Log Entry:
Dec 27 08:15:01 AS-P-18E4A6 nsp_servers[1151]: 2024-12-27 08:15:01.774 [1654641088] nsp.pin.modbus.SerTransport Flush buffer. Protocol error code = 10Error Code 7 – CRC Header Issue
Message: Flush buffer. Protocol error code = 7
Meaning:
This error indicates a CRC (Cyclic Redundancy Check) mismatch in the response message.
Possible Causes:
- Incorrect CRC calculation by the device
- Incomplete or corrupted packet
Example Log Entry:
2025-07-22 10:14:39.636 [1666360064] nsp.pin.modbus.SerTransport Flush buffer. Protocol error code = 7
