Siemens S7-1200 System Manual page 735

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Table 12- 53 MB_CLIENT protocol errors

Response code to

Modbus client

Table 12- 54 MB_CLIENT execution condition codes

MB_CLIENT parameter errors

MB_CLIENT is waiting for a Modbus server response to a connect or disconnect request, on the assigned

TCP port. This is only reported for the first execution of a connect or disconnect operation.

MB_CLIENT is waiting for a Modbus server response to a connect or disconnect request, for the assigned

TCP port. This will be reported for any subsequent executions, while waiting for completion of a connect

or disconnect operation.

A disconnect operation has successfully completed (Only valid for one PLC scan).

The server did not respond in the assigned time. MB_CLIENT must receive a response using the

transaction ID that was originally transmitted within the assigned time or this error is returned. Check the

connection to the Modbus server device.

This error is only reported after any configured retries (if applicable) have been attempted.

Invalid mode value

Invalid data address value

Invalid data length value

Invalid pointer to the DATA_PTR area. This can be the combination of MB_DATA_ADDRESS +

MB_DATA_LEN.

Pointer to a optimized DATA_PTR area (must be a standard DB area or M memory area)

The port is busy processing an existing Modbus request.

Received Modbus frame is malformed or too few bytes have been received.

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG

Data type Default

Time in seconds that the MB_CLIENT waits for a server to respond to a

Indicates whether the connection to the assigned server is connected

or disconnected: 1=connected, 0=disconnected

Modbus protocol errors

Function code not supported

Data length error

Data address error or access outside the bounds of the MB_HOLD_REG address area

Data value error

Data diagnostic code value not supported (function code 08)

Communication processor and Modbus TCP

12.5 Modbus communication