Siemens SINAMICS Series Operating Instructions Manual page 546

Descriptions of functions
10.8 Communication via Modbus TCP
Structure of a read request via Modbus function code 03 (FC 03)
Any valid register address is permitted as the start address.
Via FC 03, the control can address more than one register with one request. The number of
addressed registers is contained in bytes 10 and 11 of the read request.
Table 10- 50 Structure of a read request for device number 17, example
Value
MBAP header
03 h
00 h
6D h
00 h
02 h
The response returns the corresponding data set:
Table 10- 51 Device response to the read request, example
Value
MBAP header
03 h
04 h
11 h
22 h
33 h
44 h
Table 10- 52 Invalid read request
Read request
Invalid register address
Read a write-only register
Read a reserved register
Controller addresses more than 125 registers
The start address and the number of registers of an
address are located outside of a defined register
block
544
Byte Description
7
8 Register start address "High" (register 40110)
9 Register start address "Low"
10 Number of registers "High" (2 registers: 40110; 40111)
11 number of registers "Low"
Byte Description
7
8 Number of bytes (4 bytes are returned)
9 Data first register "High"
10 Data first register "Low"
11 Data second register "High"
12 Data second register "Low"
Inverter response
Exception code 02 (invalid data address)
Telegram in which all values are set to 0.
Exception code 03 (invalid data value)
Exception code 02 (invalid data address)
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A