USB to Serial Converters Manual
Version 2.0
Document Reference No.: CP_000032 Clearance No.: CP#022
Copyright © Connective Peripherals Pte Ltd 25
Jumper Settings
Inside the unit, there is a 7x3 (21 pin) header block. Jumpers are used to select features such as 120 Ohm
termination on Tx, Rx and CTS, and 750 Ohm biasing resistors on Tx and Rx. You will need to open up the
cover and set the jumpers as per the requirements of your application.
Enable Tx+/- Termination with 120 Ohm. This jumper should be populated for RS-
485 half-Duplex mode
Disable Tx+/- Termination
Pull-up Tx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated to
enable pull-up of Tx+
Disable Pull-up of Tx+ to VCC
Pull-down Tx- to GND by 750 Ohm Bias resistor This jumper should be populated
to enable pull-down of Tx-
Disable Pull-down of Tx- to GND
Enable Rx+/- Termination with 120 Ohm. This jumper should be populated for RS-
422 and RS-485 Full-Duplex mode
Disable Rx+/- Termination
Pull-up Rx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated to
enable pull-up of Rx+
Disable Pull-up of Rx+ to VCC
Pull-down Rx- to GND by 750 Ohm Bias resistor. This jumper should be populated
to enable pull-down of Rx-
Disable Pull-down of Rx- to GND
Enable CTS Termination with 120 Ohm. This jumper should be populated for RS-
422 mode
Table 3 - Jumpers to select Termination and Biasing
Note: If biasing of an RS-485 half-duplex bus is required, enable Rx biasing only (Pull-up Rx+ to VCC by
750 Ohm Bias resistor and Pull-down Rx- to GND by 750 Ohm Bias resistor). Tx biasing should not be used
as this would provide two sets of biasing resistors on the bus.
See the notes in section 5.1 before setting Termination and Biasing
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