Operating Instructions

Communication via RS485
5.4 Communication using Modbus RTU
Fieldbuses
138 Function Manual, 04/2018, FW V4.7 SP10, A5E34229197B AE
The response returns the corresponding data set:
Table 5- 19 Slave response to the read request, example
Value
Byte
Description
11 h
0
Slave address
03 h
04 h
11 h
22 h
33 h
44 h
1
2
3
4
5
6
Function code
Number of bytes (4 bytes are returned)
Data first register "High"
Data first register "Low"
Data second register "High"
Data second register "Low"
xx h
xx h
7
8
CRC "Low"
CRC "High"
Table 5- 20 Invalid read request
Read request
Inverter response
Invalid register address
Exception code 02 (invalid data address)
Read a write-only register
Telegram in which all values are set to 0.
Read a reserved register
Controller addresses more than 125 registers
Exception code 03 (invalid data value)
The start address and the number of registers of an
address are located outside of a defined register
block
Exception code 02 (invalid data address)
Structure of a write request via Modbus function code 06 (FC 06)
Start address is the holding register address.
Via FC 06, with one request, only precisely one register can be addressed. The value, which
is written to the addressed register, is contained in bytes 4 and 5 of the write request.
Table 5- 21 Structure of a write request for slave number 17, example
Value
Byte
Description
11 h
0
Slave address
06 h
00 h
63 h
55 h
66 h
1
2
3
4
5
Function code
Register start address "High" (write register 40100)
Register start address "Low"
Register data "High"
Register data "Low"
xx h
xx h
6
7
CRC "Low"
CRC "High"