Siemens SIMATIC S7-1200 System Manual page 1253

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MB_DATA_PTR assigns a buffer to store data read/written to/from a Modbus TCP server

The data buffer can be in a non-optimized global DB or M memory address.

For a buffer in M memory, use the standard Any Pointer format. This is in the format P#"Bit

Address" "Data Type" "Length", an example would be P#M1000.0 WORD 500.

MB_DATA_PTR assigns a communication buffer

● MB_CLIENT communication functions:

– Read and write 1-bit data from Modbus server addresses (00001 to 09999)

– Read 1-bit data from Modbus server addresses (10001 to 19999)

– Read 16-bit word data from Modbus server addresses (30001 to 39999) and (40001 to

– Write 16-bit word data to Modbus server addresses (40001 to 49999)

● Word or bit sized data is transferred to/from the DB or M memory buffer assigned by

MB_DATA_PTR.

● If a DB is assigned as the buffer by MB_DATA_PTR, then you must assign data types to

all DB data elements.

– The 1-bit Bool data type represents one Modbus bit address

– 16-bit single word data types like WORD, UInt, and Int represent one Modbus word

– 32-bit double word data types like DWORD, DInt, and Real represent two Modbus

S7-1200 Programmable controller

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

Operation and data

Reset server event counter using data diag-

nostic code 0x000A

1 word per request

word addresses

Communication processor and Modbus TCP

13.8 Legacy Modbus TCP communication

MB_DATA_ADDR