3.2 Star topology
13
3 Network Topologies
Version 2.4 04/07
Fig. 4: Network structure in a redundant optical ring topology
RS 485 bus line
Optical fiber
Terminal unit /
bus segment
OZD … P
1
2
OZD … G
1
2
(-1300)
CH 1
CH 3
T
R
CH 2
T
R
Terminal unit /
bus segment
OZD … P
1
2
OZD … G
1
2
(-1300)
CH 1
CH 3
T
R
CH 2
T
R
Terminal unit /
bus segment
OZD … P
1
2
OZD … G
1
2
(-1300)
CH 1
CH 3
T
R
CH 2
T
R
Terminal unit /
bus segment
OZD … P
1
2
OZD … G
1
2
(-1300)
CH 1
CH 3
T
R
CH 2
T
R
3.3 Redundant optical ring
䡲
Ensure that the electrical star segment is wired
carefully. Keep it as small as possible to avoid
interference injection into the electrical star
segment, and from here into the entire network.
This can be achieved by laying out the OZD Profi
12M … in the electrical star segment directly next
to each other on a hat rail.
䡲
Switch on the terminating resistors in the bus port
connectors (see 4.5.4, ”Connecting the electric RS
485 bus lines“, p. 24) at both ends of the electrical
star segment.
䡲
Do not connect a bus subscriber to the electrical
star segment wherever possible.
Modules with one or two optical ports can be used to
create an active PROFIBUS star coupler. Modules with
one optical port are sufficient for connecting a terminal
or an RS 485 bus segment to the active star coupler.
If the link monitoring on the optical ports is activated,
the fiber optic links are monitored by the respectively
connected OZD Profi 12M ….
Note:
Optical ports which are not assigned (for instance,
because they are reserved for a future system extension)
indicate a fiber break if the link monitoring is activated.
You can prevent this error report from being issued by
activating the operating mode ”Line without fiber link
monitoring “ at the non-assigned ports.
Please note that optical ports which are not connected
must always be fitted with protective caps to guard
against extraneous light and dirt.
