Enable Mode; Terminal Resistor; Figure 2.3: Com3& 4 Terminal Resistors (Jp8& 10) - Advantech UNO-1019 User Manual

2.4.2 Enable Mode

You could set the Enable mode by using DIP switches (S10). If the
switches are set to "Off", the driver automatically senses the direction of
the data flow and switches the direction of transmission. No handshaking
is necessary. If DIP switches are set to "On," the driver is always enabled,
and always in high or low status. Please must select a mode before begin-
ning RS-422 applications.
Default Setting is "Off"
Switch position
On
Off

2.4.3 Terminal Resistor

You can install terminator resistors if necessary to match impedance.
Each signal line (Tx+/Tx-/Rx+/Rx-/Data+/Data-). Especially in fields
with electric noise, installing terminal resistors is helpful to stabilize com-
munications. Make sure that both sides of the RS-422 or RS-485 commu-
nication ports are installed on BUS.
You could install jumpers on JP8 and JP10 to enable terminal resistor
(120Ohms) for RS-422 or RS-485 of COM3 and COM4. The detail
jumper setting shows as following figure.
Figure 2.3: COM3& 4 Terminal Resistors (JP8& 10)
Description
RS-422 master
RS-422 slave or
RS-485 Automatic Direction Control
11 Chapter 2