Bender FTC470XMB, Operating Manual

Page: 27 / 100

The FTC470XMB protocol converter
27 TGH1367en/06.2010
4.5.6 Communication between Modbus RTU and BMS
Description of data exchange
The communication process is regarded from the Modbus Master’s point of view. Data ex-
change between the Modbus Master and FTC470 XMB by using the Modbus functions write
(16) and read (3) in pairs. FTC470XMB only communicates via the Modbus functions read
and write.
Communication between the components is as follows:
1. The Modbus Master starts a request to the FTC470XMB with function 16
2. FTC470XMB acknowledges the request
3. The Modbus Master starts the read access to the requested data with function 3
4. FTC470XMB transmits the requested data in defined format
All addresses: 1-based
Address ranges for output and input data
●
The output data (request, write access)
of the Modbus Master are always written into the same memory section of the FTC470XMB
(Modbus Slave). This is done with the Modbus function 16 (writing of several Words). The
address is entered in decimal or hexadecimal format depending on the Modbus Master. The
address range for requests is preset:
Start address Address range
hexadecimal
1-based
0x0401 0x0401... 0x0405
decimal
1-based
1025 1025 ... 1029
hexadecimal
0-indexed
0x0400 0x0400 ... 0x0404
decimal
0-indexed
1024 1024 ... 1028
2
3
4
Modbus RTU
Master
FTC470XMB
0x0401
0x0001
1