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11
NI 9871 Operating Instructions
RS485 Bus Topology and Termination
Refer to Figure 4 and Figure 5 for an overview of 4-wire and
2-wire RS485 bus topologies and termination.
2-wire RS485 bus topologies and termination.
Figure 4. 4-Wire Full-Duplex Multidrop Network Using Terminating Resistors
Figure 5. 2-Wire Multidrop Network Using Terminating Resistors
RS485 terminators are available at
ni.com/serial
.
MASTER
Slave 1
120
Ω
Slave 2
Slave n
120
Ω
Tx
Tx
Rx
Tx
Rx
Tx
Rx
Rx
120
Ω
120
Ω
MASTER
Slave 1
120
Ω
Slave 2
Slave n
120
Ω
Tx
Tx
Rx
Tx
Rx
Tx
Rx
Rx