Siemens SIMATIC S7-1200 System Manual page 1263

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Table of Contents

Table 13- 142 MB_SERVER execution condition codes

Response code to

Modbus server

In addition to the MB_SERVER errors listed above, errors can be returned from the

underlying T block communication instructions (TCON, TDISCON, TSEND, and TRCV

(Page 857)).

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK

Modbus protocol errors

MB_SERVER is waiting for a Modbus client to connect to the assigned TCP port. This

code is reported on the first execution of a connect or disconnect operation.

MB_SERVER is waiting for a Modbus client to connect to the assigned TCP port. This

code is reported for any subsequent executions, while waiting for completion of a con-

nect or disconnect operation.

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

Invalid pointer to MB_HOLD_REG: area is too small

Pointer to an optimized MB_HOLD_REG area (must be a non-optimized DB area or M

memory area) or Blocked process timeout exceeds the limit of 55 seconds. (S7-1200

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

13.8 Legacy Modbus TCP communication