Termination Resistors And Fail-Safe Biasing Mechanism - HMS Networks Intesis INMBSDAI001I000 User Manual

Termination resistors and Fail-safe Biasing Mechanism

5.4. Termination resistors and Fail-safe Biasing Mechanism
IMPORTANT
The EIA-485 bus requires a 120 Ω termination resistor at each end to avoid signal reflections.
In order to prevent fail status detections by bus receivers when all the transmitters' outputs are in a high-
impedance state, a fail-safe biasing mechanism is required. This mechanism provides a safe status in the bus (i.e.,
a correct voltage level) when all the transmitters' outputs are in a high-impedance state.
The INMBSDAI001I000 gateway features an onboard 120 Ω termination resistor that can be activated via the DIP
switch SW 4.
NOTICE
See Dip switch SW4: Termination resistor setting (page 10)
Some Modbus RTU EIA-485 Client devices can also provide an internal 120Ω termination resistor and/or fail-safe
biasing. Check the technical documentation of the header device connected to the EIA-485 network for more
information.
USER MANUAL Version 1.0.0
INMBSDAI001I000 Modbus RTU Gateway
for more information.
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