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W&T The serial combi-port
5�3 RS422/485 mode
As opposed to RS232, an RS422 interface allows transmission
distances of up to 1000 meters. The RS485 mode allows you
to integrate corresponding 2- or 4-wire bus sytems into a
TCP/IP network with the help of the Com-Server.
1
Especially when using longer cable lengths in
industrial environments, potential differences need to be
taken into consideration. To prevent transmission problems
and hardware damage caused by this, we recommend galva-
nic isolation using an external isolator (e.g. W&T RS422/485-
Isolator Type 66201).
DIP switch settings
Mode SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8
RS422, RS485
4-wire bus master
OFF OFF OFF OFF ON Term. OFF
RS485 4-wire
automatic control
OFF ON OFF OFF ON Term. OFF
RS485 2-wire
automatic control
ON ON OFF OFF OFF Term. OFF
Pin assignment and function RS422/485, DB9 male
Pin Direction Signal Description Default function (*)
1 OUT TxD A/- Transmit Data A Data out
2 IN RxD A/- Receive Data A Data in
3 OUT RTS A/- Ready To Send A Handshake out
4 IN CTS A/- Clear To Send A Handshake in
5 --- GND Signal Ground ---
6 OUT TxD B/+ Transmit Data B Data out
7 IN RxD B/+ Receive Data B Data in
8 OUT RTS B/+ Ready To Send B Handshake out
9 IN CTS B/+ Clear To Send B Handshake in
(*) Applies only to the hardware handshake setting
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