Circutor RGU-100A - RS-485 COMMUNICATION; Connections; Modbus Protocol

36
RGU-10A , RGU-100A
Instruction Manual
8. RGU100A: RS485 COMMUNICATIONS
The RGU-100A has an RS-485 communications port. The device is equipped with the MODBUS RTU
communication protocol as standard.
8.1.- 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-100A and the master unit.
In this bus we can connect a maximum of 32 RGU-100A.
For communication with the master unit, we must use a smart RS-232 to RS-485 network protocol
converter.
B(-)
A(+)
GND
RS-232 / USB / Ethernet / Profibus ...
PC
RS-485
RS-485
RS-232
USB
Ethernet
Profibus
...
A+
B-
GND
24
23
22
24
23
22
A+
B-
GND
Figure 36: RS-485 connection diagram.
.
Note: Default values of the RS-485 communication: 115200 bps, no parity, 8 data bits and 1 stop bit.
8.2.- MODBUS PROTOCOL
Within the Modbus protocol, the RGU-100A 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.