Write And Read Access Using Function Codes - Siemens SINAMICS G150 Operating Instructions Manual

Table 6- 56 Assignment of the Modbus register for general parameter access using DS47
Register Description
40601 DS47 Control
40602 DS47 header
40603 DS47 data 1
... ...
40722 DS47 data 120
Note
Limited value range
Modbus TCP registers have a maximum 16 bit width. The values of display parameters (r
parameters) cannot always be represented with 16 bits. In these particular cases, the
maximum value that can be represented is displayed.
• Unsigned: 65535
• Signed min: -32768
• Signed max: 32767
6.12.5

Write and read access using function codes

Function codes used
For data exchange between the master and slave, predefined function codes are used for
communication via Modbus.
The Control Unit uses the following Modbus function codes:
● FC 03: Holding register to read data from the inverter
● FC 06: Write single register to write to individual register
● FC 16: Write to multiple registers to write to several registers
Structure of a Modbus TCP message
Table 6- 57
Transaction ID
Converter cabinet units
Operating Instructions, 07/2016, A5E03347396A
Access
R/W
R/W
R/W
R/W
Individual components, including Modbus Application Header (MBAP) and function code
Modbus Application Header
Protocol ID
2 bytes 2 bytes
6.12 Communication via MODBUS TCP
Unit Scaling ON/OFF text
or Value range
- -
- -
- -
- -
Application Data Unit (ADU)
Length
2 bytes
Data / parameter
- -
- -
- -
- -
Protocol Data Unit (PDU
Unit ID FCode
1 byte 1 byte 0 ... 252 bytes
Operation
Data
403