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GFK-1538H
Bus Connectors and Termination
The Network Slave Module provides the Profibus standard female 9-pin D subminiature connectors. Cable connectors
are available from most fieldbus parts distributors as "Profibus 9-pin D connectors". These connectors provide
termination resistors and a switch on the connector to enable/disable termination. Connectors with and without
termination are also available. The connectors label the connections for the twisted pair as cable A and cable B. The
following table illustrates the proper assignment of wire to connector to pin to signal.
Wire Color
Red
Green
Termination resistors are needed, as defined in Profibus Specification DIN 19245 Part 1 section 3.1.2.5.
Master
Slave
One terminator must be applied at each end of a network segment.
Master
Slave
Slave
Termination Required
(Segment 1)
Important: For proper network termination, the terminating devices must provide and maintain power. Power is
provided by the device on Pin 6 and Ground is provided on Pin 5. If power is lost to either terminating device, the network
may not operate correctly. Generally, the network master device is one of the terminating devices. The other
terminating device may be a critical slave device or a separately powered, stand-alone terminator.
VP (6)
Ru = 390 Ohms
RxD/TxD-P (3)
Rt = 220 Ohms
RxD/TxD-N (8)
Rd = 390 Ohms
DGND (5)
In addition to the termination shown above, the following compensation should be added for 12 Mbit bus technology:
110nH
To/from
another
node
110nH
Bus Grounding
Generally, it is only necessary to ensure that the cable shields are attached to ground. In most cable connectors, the
shield is attached to the metal housing of the conductor on the cable side and this is brought to ground by the metal
connector on the NIU.
In some installations with large networks or higher data rates, large ground potentials (greater than ±7V) may arise. In
these cases, it may be necessary to ensure all Profibus devices are attached to the same Protective Earth ground.
Connector
B
A
Slave
Slave
Slave
Termination Required
(Segment 1)
Repeater
Slave
Termination Required
(Segment 2)
5
9
110nH
4
8
3
7
2
6
110nH
1
Pin
Signal
3
RxD/TxD-P
5
DGND
6
VP
8
RxD/TxD-N
Slave
Slave
Slave
To/from
another
node
Nov 2019
6
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