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Impulse 2123 User Manual

Page 10

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Interface Biasing

1K-ohm pull up/pull down combination resistors bias the receiver inputs and are
handled automatically for each mode. The pull-up (PU) and pull-down (PD) resistor
settings are shown in the table below.

Mode

PU Setting

PD Setting

RS-232

Always Off

Always Off

RS-422

Always Off

Always Off

RS-485

Always On

Always On

Line Termination

A 120-ohm resistor is across the RS-422/485 input. If multiple devices are
configured in an RS-485 network, only the devices on each end should have the
termination in place.
Termination configuration is software selectable for both full- and half-duplex RS-
485. By default, line termination is disabled, and this configuration can be set by
placing a check next to ‘Enable Termination’ in the ‘RS-485 Advanced
Configuration’ field, as shown in the image below.

© Sealevel Systems, Inc.

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