Circutor RGU-100B, Instruction Manual

Page: 35 / 54

35
Instruction Manual
RGU-100B
7.- RS-485 COMMUNICATIONS
The
RGU-100B
has an RS-485 communications port. The device is equipped with the
MODBUS RTU
communication protocol as standard.
7�1�- CONNECTIONS
The RS-485 cable must be wired using twisted pair cable with mesh shield (minimum 3 wires), with a
maximum distance of 1200 meters between the
RGU-100B
and the master unit.
In this bus we can connect a maximum of 32 RGU-100B .
For communication with the master unit, we must use a smart RS-232 to RS-485 network protocol
converter.
B(-)
A(+)
S
RS-232 / USB / Ethernet / Profibus ...
PC
RS-485
RS-485
RS-232
USB
Ethernet
Profibus
...
A+
B-
GND
A+
B-
S
24
23
22
24
23
22
Figure 34: RS-485 connection diagram�
Note:
Default values of the RS-485 communication:
9600 bps
,
no parity
,
8 data bits
and
1 stop bit
.
7�2�- MODBUS PROTOCOL
Within the Modbus protocol, the
RGU-100B
uses the RTU (Remote Terminal Unit) mode.
The Modbus functions implemented in the device are as follows:
Function 0x01
: Reading a relay.
Function 0x02 : Reading input status.
Functions 0x03 and 0x04
: Reading integer registers.
Function 0x05 : Writing a relay.
Function 0x10 : Writing multiple registers.