Table of Contents
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1
Chapter
1-30
Chapter
7.
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8.
RXD/TXD-N
9.
CNTR-N
All FieldBus devices which use a standard 9-pin Sub-D connector should provide the VP
and DGND signals on the bus connector in addition to receive and transmit signals. With
all other connector types, only receive and transmit signals need to be connected.
Make sure that the connector type used is suitable for the selected baud rate.
If optional signals are provided, they must also comply with EN50170 Volume 2 and they
must be correctly described in the respective GSD file.
To prevent EMC interface from entering the device, the cable shield should be connected
to the functional ground of the device (generally the electrically conductive case). This is
done by connecting the cable shield to the metal case of the Sub-D connector and the
functional ground over a larger area. The bus connector must have a low-impedance
connection to the cable shield.
The data transfer technology of the serial bus system, which uses a shielded twisted pair
data cable, is described in the specification of the interface-immune RS 485 interface
standard. To allow correct bus termination, each station must connect the signals DGND
and VP (5V) to pins 5 and 6 of the connector respectively. The 5V supply for the
terminating resistors (VP) should have a minimum current rating of 10mA (the current load
can increase to 12mA if a NULL signal is sent through the bus). The current rating should
be increased to approximately 90mA if you need to supply other types of devices on the
bus such as bus terminals and optical fiber cable drivers. Due to the capacitive load of the
station and the resulting cable reflections, bus connectors should be provided with built-in
series inductors.
The use of an incorrect supply voltage or frequency can cause severe damage to
the component.
RSTi Network Adapter Manual User Manual - January 2012
Receive/Transmit data-minus (A-wire)
Repeater Control Signal (direction control)
Caution
GFK-2746
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