Titan Electronics Inc NETCOM423 Manuel D’Utilisation
10.3. RS422/485 E
LECTRICAL
C
ONFIGURATION
In typical RS 422 and RS 485 installations certain
electric conditions have to be configured. Simply
connecting cables is not enough to fulfil the
specifications or RS 422 and RS 485.
For ease of installations the NetCom Wireless Serial
Device Servers provide these functions for often used
parameters. They are activated by placing certain
jumpers, internal of the NetCom. There is one block of
jumpers near each serial port. Place a connection cap to
activate the function
electric conditions have to be configured. Simply
connecting cables is not enough to fulfil the
specifications or RS 422 and RS 485.
For ease of installations the NetCom Wireless Serial
Device Servers provide these functions for often used
parameters. They are activated by placing certain
jumpers, internal of the NetCom. There is one block of
jumpers near each serial port. Place a connection cap to
activate the function
Image 140:
RS422/485 Jumper
Warning: All jumpers are unconnected by default. This is important for
use in RS232 mode. Never close any jumper, otherwise communication
errors or damage of devices is possible.
use in RS232 mode. Never close any jumper, otherwise communication
errors or damage of devices is possible.
Pins Function of Signals
1-2 Place 120Ω to terminate Tx+/- (Data+/- in RS 485 2-wire)
3-4
5-6
3-4
5-6
Add BIASing function to Tx+/-
(mostly required for RS 485 2-wire modes)
(mostly required for RS 485 2-wire modes)
7-8 Place 120Ω to terminate Rx+/-
9-10
11-12
Add BIASing function to Rx+/-
Table 12: RS422/485 Jumper Configuration
10.3.1. T
ERMINATION
R
ESISTORS
The use of long communication lines in RS 422 and RS 485 mode
require the installation of termination resistors. These must match the
impedance of the cable. Typical cables in Twisted-Pair configuration
have an impedance around 120Ω. In RS 422 this resistor has to be
placed at the far end from the sender, in RS 485 the typical
configuration requires one resistor at each end of the cable.
require the installation of termination resistors. These must match the
impedance of the cable. Typical cables in Twisted-Pair configuration
have an impedance around 120Ω. In RS 422 this resistor has to be
placed at the far end from the sender, in RS 485 the typical
configuration requires one resistor at each end of the cable.
10.3.2. BIAS
F
UNCTION
RS 485 requires a BIAS option for the communication lines. This will
guarantee stable electrical levels on the cables, even at times when no
station is transmitting data. Without BIAS there will be noise on the
cable, and sometimes receivers can not detect the first characters of a
beginning communication.
guarantee stable electrical levels on the cables, even at times when no
station is transmitting data. Without BIAS there will be noise on the
cable, and sometimes receivers can not detect the first characters of a
beginning communication.
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NetCom 123 WLAN, 423 WLAN,