Huawei AR500 Series Hardware Description page 670

Huawei
AR500&AR510&AR531&AR550&1500&AR2500
Industrial Switch Routers
Hardware Description
Specifications
To meet current (lower than 2 A) and ambient temperature requirements, you are advised to
use wires with 1.0 mm
required specifications of an RS485/RS422 cable.
Table 6-26 Specifications of an RS485/RS422 cable
Conductor Type
Solid
Twisted
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.
DIP switch settings.
Table 6-27 DIP switch settings
Switch and
State
SW
ON
OFF
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
l
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.
Issue 10 (2019-03-06)
2
conductors to assemble the RS485/RS422 cable.
Pin and
State
5
Pull low
510 Ω
150 kΩ
To set the terminal resistor to 150 kohm, put pins 4 and 5 to the OFF position. (This is
the default state setting.)
To set the terminal resistor to 510 Ω, put pins 4 and 5 to the ON position.
Copyright © Huawei Technologies Co., Ltd.
Minimum Conductor
Cross-Sectional Area
2
0.5 mm or 20 AWG
2
0.5 mm or 20 AWG
Pin and Pin and
State State
4 3
Pull high Terminator
510 Ω 120 Ω
150 kΩ -
6 Cables
Table 6-26 lists
Maximum Conductor
Cross-Sectional Area
2
1.5 mm or 16 AWG
2
1.5 mm or 16 AWG
Table 6-27 describes the
Pin and Pin and
State State
2 1
Duplex
Half Half
Full Full
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