Terminating Resistance - LG GLOFA-GM Series User Manual

Chapter 3 Product specification

3.4 Terminating resistance

For communication via RS-422 channel, terminating resistance from external must be connected. Terminating resistance
has the function to prevent distortion of signal by reflected wave of cable for long-distance communication, and the same
resistance (1/2W) as characteristic impedance of cable must be connected to terminal of network.
When using the recommended cable in 3.3, connect terminating resistance of 120Ω to both ends of cable. Also when
using other cable than recommended, the same resistance (1/2W) as characteristic impedance of cable must be
connected to both ends of cable.
1) How to connect terminating resistance during RS-422 connection
GM3/4/6 unit
PLC #1
GM7 unit
RXA
RXB
TXA
TXB
SG
·
·
PLC #1
PLC #2
RXA
RXB
TXA
TXB
SG
·
·
PLC #2
3-5
PLC #(N-1)
RXA
RXA
RXB
RXB
TXA
TXA
TXB
TXB
SG
SG
·
·
·
·
PLC #(N-1) PLC #N
PLC #N