Profibus Cable Connector - Omron SYSMAC CS Series Operation Manual

Setting up a Network
Inductors
110 mH
B-Line
Network
A-Line
110 mH
2-4-3

PROFIBUS Cable Connector

Bus Cable Connector
To next
station
From
previous
station
40
intermittent data transfer errors, particularly if the bus segment is operated
close to the specified limits for maximum numbers of devices, maximum bus
segment length and maximum data transfer rate.
In addition to the bus termination, additional precautions must be taken to
ensure proper operation at high baud rates, i.e. baud rates of 500 kbit/s and
higher. Due to the capacitive load of the device and the resulting cable reflec-
tions, bus connectors must be provided with built-in series inductors, of 110
mH each, as shown in the figure on the left.
Installing the inductors applies to all devices on the network, and not only to
the devices at both ends of the bus cable.
The plug connector to be used on the CS/CJ-series PROFIBUS Master Unit is
a 9-pin male sub-D type, preferably encased in metal and having a facility to
connect the shield of the cable to the case or to pin 1. The cable should be
connected to the receive / transmit lines, pin 3 (B-line) and pin 8 (A-line).
The use of special PROFIBUS DP cable connectors, which are available from
several manufacturers, is highly recommended. Various models are widely
available, with or without the bus termination and inductors built-in. If provided
in the connector, the Bus termination can often be enabled or disabled
through a switch on the connector.
The special PROFIBUS DP cable connectors often provide a convenient way
of connecting the cables. The figure on the left, provides an example of such
a bus cable connector.
A standard 9-pin sub-D plug can only be used if the PROFIBUS Master Unit is
not at the start or the end of a bus segment, or on a stub line at a baud rate of
500 kbit/s or less.
The two PROFIBUS data lines are designated A and B. There are no regula-
tions on which cable core colour should be connected to which of the two data
terminals on each PROFIBUS device; the sole requirement is to ensure that
the same core colour is connected to the same terminal (A or B) for all
devices throughout the entire system (across all devices and bus segments).
The PROFIBUS Organization recommends the following rule for data line
colour codes: PROFIBUS cables in general will use the colours red and green
for the data lines, with the following assignment:
• Data cable wire A - green
• Data cable wire B - red
This rule applies to both the incoming and the outgoing data lines.
Section 2-4