3 Network Topologies
3.1 Line topology
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Version 2.4 04/07
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 moni-
tored by the two connected modules.
If a module fails, an optical fiber breaks or faults are
determined on the optical transfer link, the fiber link
between the two OZD Profi 12M … 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 …
is connected to the malfunctioning fiber link by the port
LEDs switching to red and by activation of the signaling
contacts. The segmentation is lifted automatically as
soon as both modules recognize that the field bus net-
work 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
formed in the event of an error. Every time the partial
networks are switched together, network malfunctions
may arise due to the double tokens or frame collisions.
Note:
If a module with two optical ports is used at the
beginning or end of a line, the optical port 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 ports which are not connected
must always be fitted with protective caps to guard
against extraneous light and dirt.
In a line structure, the individual OZD Profi 12M … are
connected together by dual-fiber optical fibers. Modules
with one optical port are sufficient at the beginning and
end of a line, between which modules with two optical
ports are necessary.
If single point-to-point connections are to be built up,
this can be achieved using two modules each with one
optical port.
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 >
_ 11 on 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 mal-
function.
Refer to the manufacturer’s manual of the terminal con-
cerned for details about how to alter the settings.
