Samson TROVIS 6495 Series Mounting And Operating Instructions page 52

Interfaces
RS-485 data transmission is implemented using SSP or Modbus RTU protocol. Slide switches
are used to set the 2-/4-wire operation and to activate bus termination.
The protocol of the RS-485 interface is set at the controller in the configuration item D.3.1.
The first time the USB interface is used to connect the controller to the computer, the device
driver is demanded. The driver is included on the TROVIS-VIEW CD-ROM (USB Driver >
USB-RS232 Adapter 8812-2001) or can be downloaded from the Internet at
www.samson.de > Services > Support & Downloads > USB driver.
Network structure
Fig. 9 shows an example for the setup of an automation system with data exchange using
Modbus protocol. A maximum of 246 devices can be addressed. First of all, a converter
must connected to the computer to convert the RS-232 signal issued by the computer into a
RS-485 signal. A repeater must be used if the line exceeds a length of 1200 m or if more
than 32 participants are connected to the bus. No more that three repeaters should be con-
nected in series. As a result, lines of 4800 m can be achieved. Ten of these lines can be con-
nected in parallel on extending the network.
Bus terminators must be fitted at the beginning and end of every section, e.g. between the
converter and repeater.
1 Converter
2 Repeater
3 Modbus device, e.g. TROVIS 6495-2
3
max.
30
3
Fig. 9 · Network structure with converters and repeaters
52
EB 6495-2 EN
1
RS-485
RS-485
RS-232
3
max.
30
3
2
RS-485
RS-485
RS-232
2
RS-485
RS-485
3
max.
30
3
3
max.
31
3
2
RS-485
RS-485