USB to Serial Converters Manual
Version 2.0
Document Reference No.: CP_000032 Clearance No.: CP#022
Copyright © Connective Peripherals Pte Ltd
29
5 - 6
Enable Rx+/- Termination with 120 Ohm. This jumper should be populated for RS-
422 and RS-485 Full-Duplex mode
7 - 8
Pull-up Rx+ to VCC by 750 Ohm Bias resistor. This jumper should be populated to
enable pull-up of Rx+
9 - 10
Pull-down Rx- to GND by 750 Ohm Bias resistor. This jumper should be populated
to enable pull-down of Rx-
11 - 12
Enable CTS Termination with 120 Ohm. This jumper should be populated for RS-
422 mode
Table 7 - 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
5.5
ES-U-3xxx-
x and ES-U-
2101-MB
This section applies to the following adapters:
•
ES-U-3001-MB
•
ES-U-3008-RM
•
ES-U-3016-RM
•
ES-U-2101-MB
See the General Notes and Warnings on page 23 before changing settings or opening the cover.
The DIP switches should be set to select the correct serial mode before connecting the converter
to your RS-232/RS-422/RS-485 serial bus.
DIP Switch Settings
On the outside of the unit, there are four DIP switches, which are used to select the required serial mode
(RS-232, RS-422 or RS-485).
Operation Mode
S1
S2
S3
S4
RS-232
OFF
ON
ON
ON
RS-422
4 Wire with handshaking
ON
ON
ON
ON
RS-485
Full Duplex (4 wire)
ON
OFF
ON
ON
Half Duplex (2 wire) with Echo
ON
OFF
OFF
ON
Half Duplex (2 wire) without Echo
ON
OFF
OFF
OFF
Table 8 - RS-232, RS-422 & RS-485 Mode Configuration
Jumper Settings
Inside the unit, there is a 7x2 (14 pin) header block for each serial port. 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.
