X2 to RS 485

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HMIs, human machine interfacesET-208Electrical Installation ET-208Connection toX2 to RS 485


The X2 ports of our devices provide you with the option of using an RS-422 or an RS-485 bus, depending on the wiring.


The RS422/RS-485 interface of the devices is provided at terminals 1-4 at the X2 and X3 terminal blocks. The signals have the following meaning:







Data/Out - the data is sent from here. Negated signal



Data/Out - the data is received here.



Data/In, this is where the data is received. Negated signal



Data/In, this is where the data is received.


In the RS-422 the only thing that is defined are the electric characteristics of the interface (OSI reference model, level 1). No standard exists for the connector pin assignment or the flow control protocol (control of data exchange, level 2), and you have to refer to the assignment information contained in the manuals of the connected devices for the exact wiring. The connected devices furthermore have to support the same protocol.


The RS-422 is mainly intended for the realisation of point-to-point connection. In process technology it is also used to realise a bus system (multi-drop) with (n) participants.


Classic point-to-point connection:




Multi-drop connection:


Device 1

Device 2

Device (n)


The EOL resistor (120 Ohm) of the receiving circuit is switched on in the cicon2 Communication parameter menu under "Termination".


The PIN configuration of the other unit will be detailed in the interface description issued by the unit's manufacturer.


cable type:

Data connection at least UTP [unshielded twisted pair] in rough environment STP [shielded twisted pair]


See also:

Kapitelseite RS422 to X2

Kapitelseite RS 485 Informations



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