Siemens SINAMICS G130 Operating Instructions Manual page 305

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 6- 51
Value
MBAP header
03 h
00 h
6D h
00 h
02 h
The response returns the corresponding data set:
Table 6- 52
Value
MBAP header
03 h
04 h
11 h
22 h
33 h
44 h
Table 6- 53
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 regis-
ter block
Inverter chassis units
Operating Instructions, 07/2016, A5E00331449A
Structure of a read request via slave number 17, example
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"
Slave response to the read request, example
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"
Invalid read request
6.11 Communication via MODBUS TCP
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)
Operation
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