3 Network Topologies
3.1 Line topology
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Version 04 05/2014
3.1.1 Line topology with optical fiber link
monitoring and segmentation
This operating mode should preferably be used if an
interrupted fiber segment is to be separated from the rest
of the network.
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Monitoring mechanisms:
Send echo:
yes
Monitor echo:
yes
Suppress echo:
yes
Monitor:
yes
Segmentation:
yes
In this operating mode the individual fiber links are
monitored by the two connected repeaters.
If a repeater fails, an optical fiber breaks or faults are
determined on the optical transfer link, the fiber link
between the two OZD Profi 12M … PRO is interrupted
(segmented).
The PROFIBUS network is divided into two partial net-
works, which remain functional independently of one
other.
The malfunction is indicated at the two OZD Profi 12M …
PRO that are connected to the malfunctioning fiber link
by the channel LEDs switching to red and by activation
of the signaling contacts. The segmentation is lifted auto-
matically as soon as both repeaters recognize that the
field bus network is functioning correctly with the help
of test frames.
Please note that in the case of networks with several
active bus subscribers, two logical token rings are for-
med in the event of an error. Every time the partial net-
works are switched together, network malfunctions may
arise due to the double tokens or frame collisions.
Note:
If a repeater with two optical channels is used at the
beginning or end of a line, the optical channel which is not
assigned must be switched to the operating mode ”Line
without fiber link monitoring“, so that it does not signal
a break in the fiber line.
Please note that optical channels which are not connec-
ted must always be fitted with protective caps to guard
against extraneous light and dirt.
In a line structure, the individual OZD Profi 12M … PRO
are connected together by dual-fiber optical fibers.
Repeaters with one optical channel are sufficient at the
beginning and end of a line, between which repeaters with
two optical channels are necessary.
If single point-to-point connections are to be built up,
this can be achieved using two repeaters each with one
optical channel.
The line topology can be realized with and without fiber
link monitoring. If both operating modes are used within
an optical fiber line, the operating mode ”Line topology
without fiber link monitoring“ determines the availability
of this fiber line. It is recommended that fiber link monito-
ring be used in homogeneous OZD Profi networks
(default factory setting).
Please note that the following ambient conditions must
be fulfilled to ensure that network configuration functions
correctly:
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The parameters MIN T
SDR
described in the
PROFIBUS standard EN 50170 must be set to
a value >
_ 11on all terminals. This is usually the
case, but the setting should be checked if com -
munication malfunctions continuously arise.
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When configuring your network, select low bus
subscriber addresses wherever possible. This
ensures that master timeout times which may
arise are kept as short as possible in the event
of a malfunction.
Refer to the manufacturer’s manual of the terminal
concerned for details about how to alter the settings.