PROFIBUS
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2.2.1    9-pin Sub-D connection (part one)

The 9-pin Sub-D connector is suitable for use inside control cabinets (IP 20). Unless using pre-made cable assemblies, the connector must be fitted to the PROFIBUS cable.

The PROFIBUS cables are normally daisy-chained through the connector. This allows PROFIBUS station connection without using T-junctions (which introduce spur lines). For this reason, PROFIBUS connectors normally have two cable entries, each with a set of terminals. Each set of terminals is normally labeled “A” and “B” or given a color reference, e.g. “green” and “red”. These two terminals connect to the two data wires in the PROFIBUS cable. The color scheme must be used consistently within a segment; i.e. the cores must not be swapped over. The PROFIBUS guideline Interconnection Technology specifies the following assignment:

 

 

A green

B red

 

 

Wiring techniques differ from manufacturer to manufacturer; these can be divided into two groups: preassembled PROFIBUS cables and field-assembled PROFIBUS cables. The wiring techniques for pre-assembled PROFIBUS cables require special tools. For this reason, you should always select a method that can be field-assembled for on-site installation. This also offers the benefit that the PROFIBUS cable can be easily reconnected in case of repair or maintenance.

For field assembled PROFIBUS cables the following technologies are used:

  1. Screw methods
  2. Insulation displacement methods
  3. Cage clamp method

The following sections provide examples of a few implemented solutions from different manufacturers. However, they do not provide full assembly instructions. You should always refer to the specific manufacturer’s instructionss.

Ensure that you are only using PROFIBUS cables approved by the connector manufacturer for use with the respective connector. This applies particularly to the use of insulation displacement technology.


At least one of the PROFIBUS connectors should have a socket for a programming or diagnostic device (piggy-back socket) which is best located at the beginning or the end of the cable (segment).

Use only Sub-D-connectors that ensures a good conducting of the shield with the connector by some grooves.

Fig.: pin assignment of 9-pin Sub-D-connector front sidet

Please scroll with your mouse over the display!

Table: pin assignment of 9-pin Sub-D-connector

Pin Signal Description Specification
Cable Device
1 (Shield) Shield or potential equalization Not recommended
2 M24 not occupied Ground of 24V power supply Optional²
3 RxD/TxD-P Receive/Transmit data; line B (red) Mandatory
4 CNTR-P not occupied Control of repeater direction Optional²
5 DGND not occupied Data ground (reference voltage to VP) Mandatory
6 VP / +5V¹ not occupied Power supply +5v (e.g. for bus termination) Mandatory
7 P24 not occupied +24V power supply Optional
8 RxD/TxD-N Receive/Transmit data; line A (green) Mandatory
9 CNTR-N not occupied Repeater Steuersignal (Senderichtungssteuerung) Optional²
¹ Minimum current capability is 10mA
² These signals should be provided by the device if converters from RS485 to fibre optic transmission are to be supported.
   
 
   
 
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