Advantech PCI Series User Manual

47 PCI Communication User Manual
Chapter 5 Pin Assignments and Wiring
5.2.3 RS-485 Signal Wiring
The RS-485 standard supports half-duplex communication. This means that just two
wires are needed to transmit and receive data. Handshaking signals, such as
request-to-send (RTS) are normally used to control the direction of the data flow and
to switch the transmission accordingly. In RS-485 mode, PCI-1602/1612/1622 cards
automatically sense the direction of the data flow and switch the transmission direc-
tion, meaning that no handshaking is necessary. Thus, you can build an RS-485 net-
work with only two wires. This RS-485 control is completely transparent to the user.
The software written for half-duplex RS-485 works without modification.
Figure 5.1 RS-485 Wiring Topology
Termination Resistor Setup
Termination resistors are onboard and can be selected by using a jumper for 120 or
300 Ω.

Advantech PCI Series Specifications

General

Brand	Advantech
Model	PCI Series
Category	Industrial Equipment
Language	English