Moxa Technologies NPort 5400 Series - Manual (Page 13)

NPort 5400 Series User’s Manual Getting Started
2-5
Adjustable Pull High/low Resistors for the RS-485 Port
In some critical environments, you may need to add termination resistors to prevent the reflection of
serial signals. When using termination resistors, it is important to set the pull high/low resistors
correctly so that the electrical signal is not corrupted. Since there is no resistor value that works for
every environment, DIP switches are used to set the pull high/low resistor values for each RS-485
port.
To set the pull high/low resistors to 150 KΩ, make sure both of the assigned DIP switches are in
the OFF position. This is the default setting.
To set the pull high/low resistors to 1 KΩ, make sure both of the assigned DIP switches are in the
ON position.
Pull high/low resistors for the RS-485 Port
1 2 3
SW
Pull High Pull Low Terminator
ON 1KΩ 1KΩ 1KΩ
Default OFF 150KΩ 150KΩ ---
ATTENTION
Do not set the resistors to 1 KΩ when using RS-232. Doing so will degrade the RS-232 signals
and reduce the effective communication distance.