Amplicon USB232U, Instruction Manual

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USB232U/485Ui
Page 8
2.3.2 Transmission Line Termination
2.3.2.1 Termination Resistors for RS422/485 Receivers
Operation of RS422/485 systems requires that the data lines be terminated at the final
receiver. The simplest termination is by a line-to-line resistor, and provision is made to connect
this 120
Ω
terminator using jumper, JP1, which is factory fitted.
Link Function
JP1 1-2 Data line terminated
JP1 2-3 Data line NOT terminated
Figure 2.4 Jumper Settings for Termination Resistor Selection
Further notes on RS422 and RS485 operation are given later in Chapter 4, 'Using the Serial
Communications Devices'
2.3.3 Jumper Factory Settings Summary
The USB485Ui interface can be reset to its factory defaults by re-configuring the device
according to the following tables.
Link Function
JP1 1-2 Data Line Terminated
JP2 2-3
JP3 2-3 Full Duplex (4 wire) operation
JP4 1-2 Receiver enabled when device is awake
JP5 1-2 Transmitter only enabled when device is transmitting
Figure 2.5 Factory Jumper Setting Summary