GMBHR168 Datasheet, PDF (25/70 Pages) List of Unclassifed Manufacturers – Mini BLOCK Housing 16 opto inputs, 8 Relay outputs

ITALIAN TECHNOLOGY
Master
+
TXRX
-
GND
120 Ω
grifo^®
2
Slave 1
+
RXTX
1 _- ^RS485 _CN6
5
GND
Slave 2
2
+
CN6
RXTX
1 RS485
-
5
GND
+5V
2+
1-
Slave n
CN6
RXTX
RS485
5
GND
FIGURE 11: RS 485 NETWORK CONNECTION EXAMPLE
Please remark that in a RS 485 network two forcing resistors must be connected across the net and
two termination resistors (120 Ω)must be placed at its extrems, respectevely near the Master unit and
the Slave unit at the greatest distance from the Master.
Forcing and terminating circuitry is installed on GMB HR168 board. It can be enabled or disabled
through specific jumers, as explained later.
For further information please refr to TEXAS INSTRUMENTS Data-Book , "RS 422 and RS 485
Interface Cicuits", the introduction about RS 422-485.
GMB HR168 Rel. 5.00
Page 17