Huawei AR550-8FE-D-H - Page 670

Specifications
To meet current (lower than 2 A) and ambient temperature requirements, you are advised to
use wires with 1.0 mm
2
conductors to assemble the RS485/RS422 cable. Table 6-26 lists
required specifications of an RS485/RS422 cable.
Table 6-26 Specifications of an RS485/RS422 cable
Conductor Type
Minimum Conductor
Cross-Sectional Area
Maximum Conductor
Cross-Sectional Area
Solid
0.5 mm
2
or 20 AWG 1.5 mm
2
or 16 AWG
Twisted
0.5 mm
2
or 20 AWG 1.5 mm
2
or 16 AWG
Pin Assignments
For RS485 connection, turn pins 1 and 2 of the DIP switch to the ON position. For RS422
connection, turn pins 1 and 2 of the DIP switch to the OFF position. Table 6-27 describes the
DIP switch settings.
Table 6-27 DIP switch settings
Switch and
State
Pin and
State
Pin and
State
Pin and
State
Pin and
State
Pin and
State
SW 5 4 3 2 1
Pull low Pull high Terminator Duplex
ON 510 Ω 510 Ω 120 Ω Half Half
OFF 150 kΩ 150 kΩ - Full Full
In some critical environments, you may need to add termination resistors to prevent serial
signal reflection. When using termination resistors, you must set the pull high/low resistors
correctly to prevent electrical signals from being corrupted. Because a specific pull/low
resistor value cannot suit all environments, the AR500 series routers use DIP switches to set
the pull high/low resistor values for the serial port.
l To set the terminal resistor to 150 kohm, put pins 4 and 5 to the OFF position. (This is
the default state setting.)
l To set the terminal resistor to 510 Ω, put pins 4 and 5 to the ON position.
Do not set the terminal resistor to 510 Ω the RS422 interface is used. This setting will degrade
the quality of RS422 signals and shortens the maximum communication distance.
Huawei
AR500&AR510&AR531&AR550&1500&AR2500
Industrial Switch Routers
Hardware Description
6 Cables
Issue 10 (2019-03-06) Copyright © Huawei Technologies Co., Ltd. 659