Moxa DA-662A-16-DP-LX [16/17] Configurable pull high low resistors for the rs 485 port

DA-662A Series Hardware Hardware Connection Description

3-4

Configurable Pull High/Low Resistors for the RS-485 Port

In some critical environments, you may need to add termination resistors to prevent the reflection of serial

signals. When using termination resistors, it is important to set the pull high/low resistors correctly so that the

electrical signal is not corrupted. The DA-662A series uses jumper settings to set the termination resistors and

pull high/low resistor values for each serial port.

To configure the termination or pull high/low resistors, you first need to open the DA-662A's chassis. You will

see 3 rows of jumper caps (as shown in the accompanying figure). The first row is for setting pull high resistors,

the second row is for setting termination resistors, and the third row is for setting pull low resistors.

Each serial port has 6 jumper caps for configuring the resistors. The pin assignments are shown in the following

table:

Jumper setting

RS485 Data + RS485 Data -

Pull High resistors

1-2: 150 kΩ

2-3: 1 kΩ

Termination

1-2: Open

2-3: 120 Ω

Pull Low resistors

1-2: 150 kΩ

2-3: 1 kΩ

To set the termination resistors to 120 Ω, make sure that PIN 2 and PIN 3 assigned to the serial port are shorted

by jumper caps.

To set the pull high/low resistors to 150 kΩ, make sure that PIN 1 and PIN 2 assigned to the serial port are

shorted by jumper caps. This is the default setting.

To set the pull high/low resistors to 1 kΩ, make sure that PIN 2 and PIN 3 assigned to the serial port are shorted

by jumper caps.