Siemens SIMATIC S7-1200 System Manual page 1205

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Table of Contents

STATUS (W#16#)

Table 13- 79 Modbus_Master execution condition codes (Modbus protocol errors)

STATUS (W#16#)

In addition to the Modbus_Master errors listed above, errors can be returned from the underlying PtP communication

instructions.

Setting the maximum record length for Profibus communication

When using a CM1243-5 Profibus Master module to control an ET 200SP or ET 200MP

Profibus device that uses an RS232, RS422, or RS485 point-to-point module, you need to

explicitly set the "max_record_len" data block tag to 240 as defined below:

Set "max_record_len" in the Send_P2P section of the instance DB (for example,

"Modbus_Master_DB".Send_P2P.max_record_len) to 240 after running

Modbus_Comm_Load.

Explicitly assigning max_record_len is only necessary with Profibus communication; Profinet

communication already uses a valid max_record_len value.

S7-1200 Programmable controller

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

Negative acknowledgement when reading module. Check the input at the PORT parameter.

This can be caused by the loss of a PROFIBUS or PROFINET distributed I/O module, either

by a station power or communication loss or a module pull.

Negative acknowledgement when writing to module. Check the input at the PORT parameter.

This can be caused by the loss of a PROFIBUS or PROFINET distributed I/O module, either

by a station power or communication loss or a module pull.

Response code from

Modbus protocol errors

Function code not supported

Data length error

Data address error or address outside the valid range of the

DATA_PTR area

Greater than 03

Data value error

Data diagnostic code value not supported (function code 08)

Function code in the response does not match the code in the request.

Wrong slave responded

The slave response to a write request is incorrect. The write request

returned by the slave does not match what the master actually sent.

Communication processor and Modbus TCP

13.5 Modbus communication