CLS200 Series User’s Guide
Chapter 2: Installation
46
EIA/TIA-485 Interface
To communicate with more than one CLS200 series controller on a controller network, or to use
communication cable lengths greater than 50 feet (15.2 m) from PC to controller, you must use
EIA/TIA-485 communications.
When using EIA/TIA-485 communications, you must attach an optically isolated EIA/TIA-232 to
EIA/TIA-485 converter to the computer.
Figure 2.26 and Figure 2.27 show the recommended system wiring. To avoid ground loops, use an
optically isolated EIA/TIA-232 to EIA/TIA-485 converter between the computer and the EIA/TIA-485
network.
EIA/TIA-485 Converter
TXA/TDA/TX-
TXB/TDB/TX+
RXA/RDA/RX-
RXB/RDB/RX+
RXA 25
RXB 23
TXA 26
TXB 24
RXA 25
RXB 23
TXA 26
TXB 24
Do not
A
B
A
B
connect
shield to
CLS200
First CLS200 Last CLS200
JU1
JU1
Personal Computer
Figure 2.26 — EIA/TIA-485 W iring
Cable Recommendations
Watlow recommends Belden 9843 cable or its equivalent. This cable includes three 24 AWG
(0.2 mm
2
) shielded, twisted pairs. It should carry signals of up to 19.2k baud with no more than
acceptable losses for up to 4,000 feet (1,220 m).
EIA/TIA-485 Network Connections
Watlow recommends that you use a single daisy chain configuration rather than spurs. Run a
twisted-pair cable from the host or the converter to the first CLS200, and from that point run a
second cable to the next CLS200, and so on. (See Figure 2.27.)
If necessary for servicing, instead of connecting each controller directly into the next, install a
terminal strip or connector as close as possible to each CLS200, run a communications cable from
one terminal strip to the next and connect the controllers to the bus with short lengths of cable.
To avoid unacceptable interference, use less than 10 feet (3 m) of cable from the terminal or
connector to the CLS200 serial port.
Some systems may experience problems with sensor signal reading if the commons of multiple
controllers are connected. See Signal Common on page 47.
Refer to Termination on page 47 for more on terminating resistors.
Connect the shield drain to earth ground only at computer or host end.
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