Communication processor and Modbus TCP
12.5 Modbus communication
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
735
RCV_TIMEOUT Real 2.0
Time in seconds that the MB_CLIENT waits for a server to respond to a
request.
Connected Bool 0 Indicates whether the connection to the assigned server is connected
or disconnected: 1=connected, 0=disconnected
Table 12- 53 MB_CLIENT protocol errors
Response code to
Modbus client
(B#16#)
Function code not supported
Data address error or access outside the bounds of the MB_HOLD_REG address area
Data diagnostic code value not supported (function code 08)
Table 12- 54 MB_CLIENT execution condition codes
1
MB_CLIENT parameter errors
7001
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.
7002
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
A disconnect operation has successfully completed (Only valid for one PLC scan).
80C8 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 data address value
Invalid data length value
818B Invalid pointer to the DATA_PTR area. This can be the combination of MB_DATA_ADDRESS +
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.
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