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HMIs, human machine interfaces ► Panel PC ET/MT-4x6... ► Electrical Installation ► Connection informations ► RS 485 information
The RS422/RS-485 interface of the devices is provided at terminals 1-8 at the X2 and X3 terminal blocks. The signals have the following meaning:
Pin
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Name
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Definition
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1
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TxD-b
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Data/Out - the data is sent from here. Negated signal
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2
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TxD-a
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Data/Out - the data is received here.
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3
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RxD-b
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Data/In, this is where the data is received. Negated signal
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4
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RxD-a
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Data/In, this is where the data is received.
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5
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TxD-b'
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Direct connection to TxD-b, *1
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6
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TxD-a'
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Direct connection to TxD-ab, *1
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7
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RxD-b'
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Direct connection to RTxD-b, *1
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8
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RxD-a'
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Direct connection to RTxD-a, *1
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*1)
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required for the provision of an RS-485 bus.
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The X2 and X3 ports of our HMIs provide you with the option of using an RS-422 or an RS-485 bus, depending on the wiring. Below is an example of how this works with an RS-485.
The RS-485 (today: EIA-485) provides a data transfer interface with differentiated signals. Please note that the RS-485 bus is a bi-directional interface. This means that the interface sends and receives data. Connected devices therefore have to ensure communication can take place.
The following illustration shows how it should be connected to the interface:
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Pins 1-5, 2-6, 3-7, 4-8 are already internally connected.
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The maximum length of the data transmission cable is 1000m.
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 Schalter für den Busabschluß ET/MT-xx6-A-... from rev. 3.0.2
The S3 & S4 dip switches activate the bus termination resistors of the COM1/COM2 with an RS-422 or RS-485 connection.
Seriall interface COM1:
Switch
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Position
|
Interface
|
Function
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S3-1
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OFF
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COM1
RS-422/485
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No bus terminator resistor set
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ON
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Bus terminator resistor TxD line
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S3-2
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OFF
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No bus terminator resistor set
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ON
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Bus terminator resistor RxD line
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S4-1
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S4-2
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S4-3
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Interface
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Keying
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0
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0
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0
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RS-422
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Automatic keying
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0
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1
|
0
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Keying always on
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0
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0
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1
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Keying enabled by SW
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0
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1
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1
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Driver inactive
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1
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0
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0
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RS-485
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Automatic keying
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1
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1
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0
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Status not permitted
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1
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0
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1
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Keying enabled by SW
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1
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1
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1
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Driver inactive
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Touch switched off:
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S4-4 *
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OFF
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Touch *
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Touch switched off
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ON
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Touch switched on
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Seriall interface COM2:
Schalter
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Position
|
Interface
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Funktion
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S3-1
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OFF
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RS-422/485
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No bus terminator resistor set
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ON
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Bus terminator resistor TxD line
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S3-2
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OFF
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No bus terminator resistor set
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ON
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Bus terminator resistor RxD line
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S4-1
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S4-2
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S4-3
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Interface
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Keying
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0
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0
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0
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RS-422
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Automatic keying
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0
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1
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0
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Keying always on
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0
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0
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1
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Keying enabled by SW
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0
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1
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1
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Driver inactive
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1
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0
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0
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RS-485
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Automatic keying
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1
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1
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0
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Status not permitted
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1
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0
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1
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Keying enabled by SW
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1
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1
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1
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Driver inactive
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Function:
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S4-4
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-
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-
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not used.
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Schalter für den Busabschluß ET/MT-xx6-A-... to rev. 3.0.1
The S3 dip switches activate the bus termination resistors of the COM1 with an RS-422 or RS-485 connection.
Switch
|
Position
|
Interface
|
Function
|
S3-1
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OFF
|
COM1
RS-422/485
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No bus terminator resistor set
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ON
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Bus terminator resistor TxD line
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S3-2
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OFF
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No bus terminator resistor set
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ON
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Bus terminator resistor RxD line
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S4-1
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S4-2
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S4-3
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Interface
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Keying
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0
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0
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0
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RS-422
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Automatic keying
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0
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1
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0
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Keying always on
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0
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0
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1
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Keying enabled by SW
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0
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1
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1
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Driver inactive
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1
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0
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0
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RS-485
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Automatic keying
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1
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1
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0
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Status not permitted
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1
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0
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1
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Keying enabled by SW
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1
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1
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1
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Driver inactive
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Touch switched off:
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S4-4 *
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OFF
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Touch *
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Touch switched off
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ON
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Touch switched on
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*
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It is currently not possible to switch off the touch via the S4-4 dip switch.
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Schalter für den Busabschluß ET/MT-xx6 und ET/MT-xx6-Fx/Tx
The S3 and S4 dip switches activate the bus termination resistors of the COM1 and the COM2 with an RS-422 or RS-485 connection.
Switch
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Position
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Interface
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Function
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S3-1
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OFF
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COM1
RS-422/485
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No bus terminator resistor set
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ON
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Bus terminator resistor TxD line
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S3-2
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OFF
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No bus terminator resistor set
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ON
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Bus terminator resistor RxD line
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S4-1
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OFF
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COM2
RS-422/485
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No bus terminator resistor set
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ON
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Bus terminator resistor TxD line
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S4-2
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OFF
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No bus terminator resistor set
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ON
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Bus terminator resistor RxD line
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If the HMIs communicate via MPI,
the S3-1 and S4-1 dip switches must NOT be set to ON.
Otherwise, communication between PLC and control system
cannot be guaranteed to run smoothly.
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The PIN configuration of the other unit will be detailed in the interface description issued by the unit's manufacturer.
cable type:
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Data connection at least UTP [unshielded twisted pair] in rough environment STP [shielded twisted pair]
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