Applied Motion SV7-C-CE - Manual (Page 18)

18
SV7 Hardware Manual 920-0012F
12/18/2014
Connecting to a host using RS-485 option card
RS-485 allows you to connect more than one drive to a single host PC, PLC, HMI
or other computer. It also allows the communication cable to be long (more than
1000 feet). But the device to which you connect must have an RS-422 or RS-485
port.
The RS-422/485 pin diagram is shown to the right. Wiring diagrams can be found below. We
recommend the use of Category 5 cable. It is widely used for computer networks, it is inexpensive,
easy to get and certified for quality and data integrity.
The SV drives can be used with either two wire or four wire RS-485 implementations. The connec-
tion can be point to point (i.e. one drive and one host) or a multi-drop network (one host and up
to 32 drives).
Four wire systems utilize separate transmit and receive wires. One pair of wires must connect the
host computer’s transmit signals to each drive’s RX+ and RX- terminals. Another pair connects the
TX+ and TX- drive terminals to the host computer’s receive signals. A logic ground terminal is pro-
vided on each drive and can be used to keep all drives at the same ground potential. This terminal
connects internally to the DC power supply return (V-), so if all the drives on the RS-485 network
are powered from the same supply it is not necessary to connect the logic grounds. You should
still connect one drive’s GND terminal to the host computer ground.
Four wire systems are better than two wire types because the host can send and receive data at the
same time, increasing system throughput. Furthermore, the host never needs to disable its transmit-
ter, which simplifies your software. We recommend that a 120 ohm terminating resistor be con-
nected between RX+ and RX- at the farthest drive from the host.
RS-485 Four Wire System
RX+ RX
–
TX
–
TX+
GND
RS-485/422
+RX- +TX- GND +RX- +TX- GND +RX- +TX- GND
to PC TX+
to PC TX-
to PC RX+
to PC RX-
to PC GND
Drive #1 Drive #2 Drive #3
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