USB to Serial Converters Manual
Version 2.1
Document Reference No.: CP_000032 Clearance No.: CP#022
Copyright © Connective Peripherals Pte Ltd
14
10 - 11
Enable Rx+/- Termination with 120 Ohm (see notes below table)
11
–
12
Disable Rx+/- Termination
13
–
14
Enable Pull-up of Rx+ to VCC by 750 Ohm Bias resistor (see notes below table)
14
–
15
Disable Pull-up of Rx+ to VCC
16
–
17
Enable Pull-down of Rx- to GND by 750 Ohm Bias resistor (see notes below table)
17
–
18
Disable Pull-down of Rx- to GND
19
–
20
Enable CTS Termination with 120 Ohm (populate for RS422 mode if termination is
required)
20 - 21
Disable CTS Termination
Table 3 - Jumpers to select Termination and Biasing
Note on Termination:
For RS485 half-duplex, if termination is required, only Tx Termination should be enabled as the Tx and
Rx lines are linked. Enable Tx+/- termination (jumper 1-2) and disable Rx+/- termination (jumper 11-
12).
For RS485 full-duplex and RS422, termination can be enabled/disabled for Tx+/- and Rx+/- pairs
independently using the jumpers as required. See the notes on Termination in section 4.1 before setting
these options
Note on Biasing:
For RS485 half-duplex, if biasing is required, enable Tx+/- biasing only (jumper 4-5 and 7-8) and disable
Rx+/- biasing (jumper 14-15 and 17-18).
For RS485 full-duplex and RS422, biasing can be enabled/disabled for Tx+/- and Rx+/- pairs
independently as required. See the notes on Biasing in section 4.1 before setting these options.
4.3
ES-U-2xxx-M and ES-U-2xxx-RM with 3 DIP Switches
This section applies to the following adapters:
•
ES-U-2002-M
•
ES-U-2102-M
•
ES-U-2008-M
•
ES-U-2016-RM
See the General Notes and Warnings on page 12 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-422/RS-485 serial bus.
DIP Switch Settings
On the outside of the unit, there are three DIP switches, which are used to select the required serial
mode (RS-422 or RS-485).
Operation Mode
S1
S2
S3
RS-422
4 Wire with handshaking
ON
ON
ON
RS-485
Full Duplex (4 wire)
OFF
ON
ON
Half Duplex (2 wire) with Echo
OFF
OFF
ON
Half Duplex (2 wire) without Echo
OFF
OFF
OFF
Table 4 - RS-422 & RS-485 Mode Configuration
