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Termination Resistor Diagram
Termination is designed to
mitigate noise from the
RS-422/485 transmission
signals. If the network cable is
too long, undesirable
transmission-line effects will
arise. The best method for
mitigating energy on an unused
conductor is to dissipate the
energy as heat by terminating both ends of the unused conductor to ground with
resistors (so-called bi-directional termination). The resistance of the resistors
should be equal to the characteristic impedance of the line. The most common
RS-485 twisted pair has a characteristic impendence of 100-120 Ohm. Moxa's
termination technique is bi-directional termination, which offers excellent signal
integrity. With this technique, the line drivers can be located anywhere on the
network.
Function Diagram
TxD
RxD
RS-232
RTS
Line Driver
CTS
GND
Communication
Controller
ADDC
Logic
Isolation
Termination Resistor:
S3 On to Enable
S3 Off to Disable
RS-422/485
Line Driver
Installation
R
RxD+
RxD-
TxD+
-
TxD
RxD+ (Data +)
-
-
RxD
(Data
)
2-7
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