ES-U-2016-RM EasySync, ES-U-2016-RM Datasheet - Page 14

• Manufacturer Part Number: ES-U-2016-RM
• Description: USB Interface IC USB to 16 Ports RS422/RS485, Metal
• Manufacturer: EasySync

Document Reference No.: ES_000061
USB to Serial Converters Manual
Version 1.2
# 35
Clearance No.: ES
5
Switch and Jumper Settings
This section applies to ES-U-2xxx-x and ES-U-3xxx-x converters, which can be configured for different
interface types. These converters have DIP switches and internal jumpers to select the required interface.
The following pages give details of the settings required for each particular model of converter.
Ensure that you refer to the correct section for your model of converter. The relevant model numbers are
listed at the top of each section. Please also read the general notes and warnings on this page before
proceeding to configure your device.
5.1
General Notes and Warnings
Safety
For ES-U-xxxx-RM models with internal power supplies, the power cable must be disconnected before
removing the cover. Avoid contact with the power supply board inside the converter. In common with all
switching power supplies connected to the mains (120/240VAC), the power supply board in these
products can remain charged with dangerous voltages for some time after the power input is
disconnected.
Serial Bus Configuration
It is important to configure the DIP switches and jumpers to select the correct type of serial bus (RS-232,
RS-422 or RS-485) for your application before connecting the ES-U-xxxx-x converter to your serial bus.
Otherwise damage can occur to the converter or other equipment on the RS-232/RS-422/RS-485 bus.
To avoid damage, the power supply (or power cable in rack-mount units), serial cables and USB cable
should be disconnected from your converter before changing DIP switch settings and before opening the
case to change jumper settings.
Termination
For RS-422 or RS-485, it may be necessary to enable termination of the data transmission lines. This
depends on the way in which your network is connected and if termination is already provided by other
devices on the network. Before applying the termination, check your cable specification for proper
impedance matching.
Termination is normally used in the node at each end of the bus, but nodes in the middle of the bus
should not have termination enabled. The ES-U-xxxx-x converters have jumpers (or DIP switches) to
allow internal termination resistors to be enabled if required. This avoids the need to provide an external
resistor at the ES-U-xxxx-x end of the bus.
ES-U-xxxx-x converters have jumpers/switches for both Tx +/- termination and Rx +/- termination.
When using RS-485 half-duplex, only the Tx +/- termination should be enabled as indicated by the
comments in the jumper / switch setting tables for each product.
Biasing
For RS-485 half-duplex, it may be necessary to enable biasing of the data transmission lines. In some
cases, the RS-485 lines may float to undefined levels when no transmitter is active, and this can cause
additional unexpected characters to appear at the start or end of a message. Biasing resistors are used to
set a defined logic level on the serial lines when no node is transmitting.
Some ES-U-xxxx-x models feature internal 750 ohm resistors with jumpers to enable/disable them.
These should be disabled if another device on your serial bus already provides biasing as biasing of data
lines must only occur at a single point in the cabling. They are not required in RS-422 or RS-485 full-
duplex, since the transmitter is always enabled.
ES-U-xxxx-x converters have four jumpers to select biasing on Tx+, Tx-, Rx+ and Rx-. Section 5
describes these in more detail. For half-duplex RS-485, only the jumpers for Rx biasing (Pull up of Rx+
and Pull down of Rx-) should be fitted. The jumpers for Tx biasing (Pull up of Tx+ and Pull down of Tx-)
should not be fitted as this would provide two biasing resistors per line.
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