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3.5 RS-422/485 Termination Resistors Option for NCOM-113-
M/NCOM-112-M
In some critical environments, when transmitted RS-422/485 signals arrive at the
end of a cable, they are reflected. This causes the signals to travel on the cable more
than once, which is called ringing. This can cause false reading of transmitted data.
For long cables, termination resistors are required. These increase the damping in
order to reduce reflections. The value of the termination resistor must match the
impedance of the cable, which is typically 120
Ω
. Generally, this must be done in the
cabling, since this depends on the installation of connections. Before applying the
option, check your cable specification for proper impedance matching.
Inside NCOM-113-M/NCOM-112-M, there are two 3-pin header blocks (JP4, JP5) for
jumper caps to enable TxD+/-, RxD+/- 120
Ω
termination resistors. You will need to
open up the case and set the jumper settings for RS-422 mode or RS-485 mode, as
per the requirements of your application.
Settings are listed as follows:
Jumper
Function
JP4 1-2
Enable
Enable TxD+/- 120
Ω
termination resistor.
2-3
Disable
Disable TxD+/- 120
Ω
termination resistor.
JP5 1-2
Enable
Enable RxD+/- 120
Ω
termination resistor.
2-3
Disable
Disable RxD+/- 120
Ω
termination resistor.
The NCOM serial device server hardware installation is now complete. Please
proceed to the next step to start the first time configuration of NCOM-113-M.
