Unidrive M SI-PROFIBUS User Guide 17
Issue Number: 3
Safety
information
Introduction
Mechanical
installation
Electrical
installation
Getting
started
Parameters
GSD
Files
Cyclic data
Non-cyclic
data
Control and
status words
Diagnostics
PROFIdrive
profile (V4)
Advanced
features
Legacy
features
Glossary of
terms
Index
4.7 Maximum network length / device loading
The maximum number of devices that can be connected to a single PROFIBUS-DP
network segment is 32, this includes all nodes and any repeaters. The maximum
lengths of cable for a segment depend on the data rate and are shown in Table 4.2.
Repeaters or fiber optic segments can be used to extend the network, allowing more
than 32 nodes to be connected on the network. The maximum number of nodes on a
single network is 125.
Table 4.2 PROFIBUS-DP maximum network cable lengths
4.8 Node addressing
SI-PROFIBUS has a valid address range of 1 to 125. Addresses 126 and 0 are reserved
for system use and should not be used. The addressing scheme used is at the
discretion of the end user however it is recommended that nodes are numbered in order
as they appear on the physical network. It is not necessary to use consecutive numbers
and gaps in the addressing scheme may be left to allow for future expansion.
4.9 Spurs
The PROFIBUS-DP specification allows spurs at data rates less than 1.5 Mb/s. At data
rates below 1.5 Mb/s there are specific requirements for capacitance and length of cable
allowed when using spurs. Control Techniques recommend that spurs are not used as
extreme care is required at the design stage to avoid network problems. More
information on spurs can be found on the PROFIBUS website at www.profibus.com.
4.10 Minimum node to node cable length
The minimum recommended node to node distance is one metre of network cable.
This distance is necessary to avoid multiple nodes generating a single large reflection
on the network, using less than one metre of cable between nodes can have serious
implications for network reliability.
4.11 Grounding
Refer to the relevant Drive User Guide for more information.
For full details on designing and installing a PROFIBUS-DP network, refer to Installation
Guidelines for PROFIBUS-DP/FMS. This document is available from the PROFIBUS
website at www.profibus.com.
Data rate Maximum trunk length
(bits/s) (m)
12M 100
6.0M 100
3.0M 100
1.5M 200
500k 400
187.5k 1000
93.75k 1200
45.45k 1200
19.2k 1200
9.6K 1200
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