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HMIs, human machine interfaces ► Thin Client ET/MT-5x6 ► Connection informations ► RS 422 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
|
Name
|
Definition
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1
|
TxD-b
|
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
|
RxD-b
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Data/In, this is where the data is received. Negated signal
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4
|
RxD-a
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Data/In, this is where the data is received.
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5
|
TxD-b'
|
Direct connection to TxD-b, *1
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6
|
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-422.
The RS-422 (today: EIA-422) provides a data transfer interface with differentiated signals. The following illustrations shows how it should be connected:
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 Switch for bus termination 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
|
Position
|
Interface
|
Function
|
S3-1
|
OFF
|
COM1
RS-422/485
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No bus terminator resistor set
|
ON
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Bus terminator resistor TxD line
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S3-2
|
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
|
Interface
|
Keying
|
0
|
0
|
0
|
RS-422
|
Automatic keying
|
0
|
1
|
0
|
Keying always on
|
0
|
0
|
1
|
Keying enabled by SW
|
0
|
1
|
1
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Driver inactive
|
1
|
0
|
0
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RS-485
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Automatic keying
|
1
|
1
|
0
|
Status not permitted
|
1
|
0
|
1
|
Keying enabled by SW
|
1
|
1
|
1
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Driver inactive
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Touch switched off:
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S4-4 *
|
OFF
|
Touch *
|
Touch switched off
|
ON
|
Touch switched on
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Seriall interface COM2:
Schalter
|
Position
|
Interface
|
Funktion
|
S3-1
|
OFF
|
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
|
OFF
|
No bus terminator resistor set
|
ON
|
Bus terminator resistor RxD line
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S4-1
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S4-2
|
S4-3
|
Interface
|
Keying
|
0
|
0
|
0
|
RS-422
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Automatic keying
|
0
|
1
|
0
|
Keying always on
|
0
|
0
|
1
|
Keying enabled by SW
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0
|
1
|
1
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Driver inactive
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1
|
0
|
0
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RS-485
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Automatic keying
|
1
|
1
|
0
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Status not permitted
|
1
|
0
|
1
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Keying enabled by SW
|
1
|
1
|
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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Switch for bus termination 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
|
OFF
|
COM1
RS-422/485
|
No bus terminator resistor set
|
ON
|
Bus terminator resistor TxD line
|
S3-2
|
OFF
|
No bus terminator resistor set
|
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
|
Interface
|
Keying
|
0
|
0
|
0
|
RS-422
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Automatic keying
|
0
|
1
|
0
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Keying always on
|
0
|
0
|
1
|
Keying enabled by SW
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0
|
1
|
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
|
1
|
0
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Status not permitted
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1
|
0
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1
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Keying enabled by SW
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1
|
1
|
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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Switch for bus termination ET / MT-xx6-A and 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
|
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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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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