Installation In The Profibus Dp Network; Baud Rates; Addressing; Cable - WEG CFW500 User Manual

3 INSTALLATION IN THE PROFIBUS DP NETWORK

The Profibus DP network, such as several industrial communication networks, for being many times applied in
aggressive environments with high exposure to electromagnetic interference, requires that certain precautions
be taken in order to guarantee a low communication error rate during its operation. Recommendations to
perform the product connection in this network are presented next.
3.1

BAUD RATES

The Profibus DP protocol defines several baud rates that can be used, from 9.6 kbit/s up to 12Mbit/s. The
maximum allowed transmission line length depends on the used baud rate, and this correlation is showed on
the table 3.1.
All equipments in the network must use the same baud rate. The CFW500 Profibus DP interface has automatic
baud rate detection, according to what has been configured for the network master, and therefore it is not
necessary to configure this option.
It is possible to observe the baud rate detected by the board at the parameter P0963.
3.2

ADDRESSING

Every device in a Profibus DP network, master or slave, is identified through a network address. This address
must be different for each device.
The CFW500 Profibus DP address is configured through the parameter P0918.
3.3

CABLE

It is recommended that the installation be carried out with a type A cable, whose characteristics are described i n
the table 3.2. The cable has a pair of wires that must be shielded and twisted, in order to guarantee higher
immunity against electromagnetic interference.
3.4

CONNECTORS

Several connector types can be used for the network connection of the equipment, from simple screw
connectors up to very specific connector types for the Profibus network.
The connector used in the CFW500 Profibus DP accessory is presented at item 3.4.
3.5

CONNECTION TO THE NETWORK

The Profibus DP protocol, by using the RS-485 physical medium, allows the connection of up to 32 devices per
segment without the use of repeaters. By using repeaters, up to 126 addressable equipments can be
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Table 3.1: Baud rate x segment length
Baud Rate
(kbit/s)
9,6; 19,2; 45,45; 93,75
187,5
500
1500
3000, 6000, 12000
Table 3.2: Type A cable properties
Impedance
Capacitance
Loop resistance
Cable diameter
Wire cross section
Segment Length
(m)
1200
1000
400
200
100
135 a 165 Ω
30 pf/m
110 Ω/km
> 0.64 mm
> 0.34 mm