Figure 3–25: CPU MODULE COMMUNICATIONS WIRING
b) RS485 PORTS
RS485 data transmission and reception are accomplished over a single twisted pair with transmit and receive data alternat-
ing over the same two wires. Through the use of these ports, continuous monitoring and control from a remote computer,
SCADA system or PLC is possible.
To minimize errors from noise, the use of shielded twisted pair wire is recommended. Correct polarity must also be
observed. For instance, the relays must be connected with all RS485 "+" terminals connected together, and all RS485 "–"
terminals connected together. Though data is transmitted over a two-wire twisted pair, all RS485 devices require a shared
C30 Controller System