Siemens SINAMICS G130 - Write and Read Access Using Function Codes

Operation
6.11 Communication via MODBUS TCP
Inverter chassis units
304 Operating Instructions, 07/2016, A5E00331449A
Table 6- 49 Assignment of the Modbus register for general parameter access using DS47
Register
Description
Ac-
cess
Unit
Scaling
ON/OFF text
or Value range
Data / parameter
40601
DS47 Control
R/W
-
-
-
-
40602 DS47 header R/W - - - -
40603
DS47 data 1
R/W
-
-
-
-
…
…
40722
DS47 data 120
R/W
-
-
-
-
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 disp
layed.
•
Unsigned: 65535
•
Signed min: -32768
•
Signed max: 32767
6.11.5
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- 50 Individual components, including Modbus Application Header (MBAP) and function code
Application Data Unit (ADU)
Modbus Application Header
Protocol Data Unit (PDU
Transaction ID
Protocol ID
Length
Unit ID
FCode
Data
2 bytes
2 bytes
2 bytes
1 byte
1 byte
0 ... 252 bytes