4 Network topologies
4.1 Line topology
20
OZD Profi G12D... ATEX 1 V. 03 07/2014
4.1.1 Line topology with fibre optic path
monitoring and segmentation
Use this operating mode preferably if a faulty fibre optic
segment should be separated from the remaining net-
work.
Monitoring mechanisms:
Transmit echo:
yes
Monitor echo:
yes
Suppress echo:
yes
Monitor:
yes
Segmentation:
yes
In this operating mode, individual fibre optic paths are
monitored by both the modules connected to it.
If a repeater breaks down or an optical fibre breaks or
there is a fault in the optical transmission path , fibre optic
path between both OZD Profi G12D... ATEX 1 is broken
(segmented).
The PROFIBUS network disintegrates into two subnet-
works, which each in itself - remains operational.
Fault is signalled by switching the channel LED to red
and activation of the signalling contact of both OZD Profi
Line topology can be implemented with and without fibre
optic path monitoring. If both operating modes are used
within a fibre optic line, the operating mode “line topolo-
gy without fibre optic path monitoring” determines the
availability of this fibre optic line. In homogenous OZD
Profi networks, it is recommended to use the fibre optic
path monitoring (factory setting).
Kindly note that following basic conditions must be com-
plied with for a proper operation during network
configuration:
Parameters MIN T
SDR
specified in the PROFIBUS
standard EN 50170 must be set at value >
_ 11 for
all terminal equipment. This is generally the case,
however, it must be checked at occurrence of per-
manent communication interferences.
When configuring your network, select possibly
low bus station addresses, in order to keep poten-
tial master time-outs small.
For changing the settings, kindly refer to the manufactur-
ers documentation related to connected terminal equip-
ment.
4.1.2 Line topology without fibre optic
path monitoring
Use this operating mode, if you connect a OZD Profi
G12D... ATEX 1 with another fibre optic network com -
ponent as per PROFIBUS directive (optical/electrical
con verter), which does not transmit a telegram echo and
does not expect or take any telegram echo.
G12D... connected to the faulty fibre optic path. Seg-
mentation is automatically can celled as soon as both the
repeaters detect the uninterrupted segmented fieldbus
subnetwork with the help of test telegrams.
Note that in case of fault, two logical token rings are
formed for networks with several active bus stations.
Each interconnection of the two sub networks may thus
lead to temporary network failure due to double token or
telegram collisions.
Note:
If a line repeater with two optical channels is used at the
beginning or the end, the non-allocated optical channel
must be switched to the operating mode “line without
fibre optic path monitoring”, so that it does not lead to a
fibre breakage signalling.
Note that optical channels, which are not connected
must be always protected with protective caps from
external light incidence and dirt.
Monitoring mechanisms:
Transmit echo:
no
Monitor echo:
no
Suppress echo:
no
Monitor:
no
Segmentation:
no
Individual fibre optic paths are not monitored in this
operating mode.
