GE B90 Instruction Manual page 71

3 HARDWARE
For the 9G/9H CPU, the 10Base-T port can only be used when the CH1 10Base-F fiber has been removed. The
10Base-T Ethernet cable and the CH1 10Base-F fiber cable cannot both be installed at the same time.
NOTE
For the 9J/9K CPU, the 10/100Base-T port has the lowest priority and is only active if both CH1 and CH2 fiber links
are down. Installation of the 10/100Base-T Ethernet cable at the same time as the CH1 and/or CH2 100Base-F
fiber cables does not affect the communication over the CH1 or CH2 fiber ports.
Figure 3–20: CPU MODULE COMMUNICATIONS WIRING (APPLICABLE MODULE DEPENDS ON ORDER CODE)
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
GE Multilin B90 Low Impedance Bus Differential System
3.2 WIRING
3
3-21