Control Technology 2500 Series Installation And Operation Manual page 45

Pin no. Signal
1 Shield
2 M24
3 RxD/TxD-P *)
4 CNTR-P
5 DGND *)
6 VP *)
7 P24
8 RxD/TxD-N *)
9 CNTR-N
Make sure that the connector type used is suitable for the selected baud rate.
To prevent EMC interference 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
large 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 interference-immune RS 485 interface standard. To allow correct bus termination,
each station must connect the signals DGND and VP (5 V) to pins 5 and 6 of the connector,
respectively. The 5 V supply for the terminating resistors (VP) should have a minimum current rating
of 10 mA (the current load can increase to 12 mA if a NULL signal is sent through the bus).The current
rating should be increased to app. 90 mA if you need to be able 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 as shown below. Due to the built-in series inductors in the bus
connectors, all bus connectors in the network should be attached to fieldbus devices to ensure that the
necessary capacitive load is provided by the device input capacitance.
CTI 2500-RBC Installation and Operation Guide V1.6
Significance
Shield/functional ground
Ground for +24 V output voltage
Receive/Transmit data – plus (B wire)
Repeater control signal (direction control), RTS signal
Data ground (reference potential for VP)
Supply voltage - plus (P5V)
Output voltage +24 V
Receive/Transmit data – minus (A wire)
Repeater control signal (direction control)
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