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3.3
RS422 interface
RS422 is destined for two point connection. The signal is symmetric, differential.
Each signal is distributed over its twisted pair. The wires are marked for instance
Rx1+ and Rx1-. In idle state (which is according to stop bit in assynchronneus
mode) the potential of Rx1+ is higher than the potential of Rx1-. The connector is
described in following table:
contact
signal
1
Rx1+
2
Rx2+
3
Tx1+
4
Tx2+
5
GND
6
Rx1-
7
Rx2-
8
Tx1-
9
Tx2-
To improve the transfer over the RS422 line the terminating resistors 100 -120 Ω
can be connected between the corresponding pair of wires. The installation of
terminators is very easy by the switching on the
switches on the back side of multiplexer.
The maximum cable length between end device
and multiplexer must not exceed 1200 m.
Multiplexer can work without any setting – the
data rate can be any in the range from 0 to
230 000 bps. The transfer does not depend on
other channels and on the communication
protocol.
3.4
Two multiplexers interconnection
The optic cable is connected through the SC connector (models E247, E249,
E24A, E24B), or ST one (models E246, 249). The remote multiplexer's
transmitter must be connected to local receiver and remote receiver must be
connected to local transmitter (the fibers are crossing). The correctly connected
multiplexers are indicated by LINK indicator.
meaning
received data of the 1st RS422
received data of the 2nd RS422
transm. data of the 1st RS422
transm. data of the 2nd RS422
ground
received data of the 1st RS422
received data of the 2nd RS422
transm. data of the 1st RS422
transm. data of the 2nd RS422
direction
from the multiplexer
from the multiplexer
into the multiplexer
into the multiplexer
from the multiplexer
from the multiplexer
into the multiplexer
into the multiplexer
SW
5-8
5
ELOE246,7,8,9,A,BZKE001
terminated line
1
On= Rx1
2
On=Rx2
3
On=Tx1
4
On=Tx2
not used
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