Profibus Electrical Interface; Rio3-Pba - Hitachi HX-RIO3 Series User Manual

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6.2. PROFIBUS Electrical Interface

6.2.1. RIO3-PBA

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 the receive and transmit signals. With all other connector types, only the
receive and transmit signals need to be connected. Make sure that the connector type used is suitable for the
selected baud rate. If optional signal is 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 connectors,
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 app. 90mA if you need to be able to supply other types of devices on the bus such as bus
terminals and optical fibre 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 as shown below.
Dsub 9
(Female)
1
2
3
4
5
6
7
8
9
The use of an incorrect supply voltage or frequency can cause severe
damage to the component.
Signal
Name
-
RXD/TXD-P Receive/Transmit data-plus(B wire)
Repeater control signal(direction control),
CNTR-P
RTS signal
DGND Data ground(reference potential for VP)
VP Supply voltage-Plus(P5V)
-
RXD/TXD-N Receive/Transmit data-minus(A-wire)
CNTR-N Repeater Control Signal(direction control)
HX-RIO3 Series
Description