2 General Functions 2.2 Operating mode related functions
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Version 2.4 04/07
Line monitoring with echoes
The modules enable the connected optical paths to be
actively monitored for interruptions in the fiber line by
means of the functions ”Send echo“, ”Monitor echo“ and
”Suppress echo“.
Send echo
A frame which is received by a module via any port is
transmitted to all other ports. If the receiving port is an
optical port, the module sends the frame back to the
corresponding optical sender.
Monitor echo
If a module sends a frame - no echo! – to an optical port,
the module expects to receive an echo. If the echo is not
received after a predefined time, an echo monitoring
error is indicated by a red LED belonging to the port.
Suppress echo
The relevant receiver is separated from the other ports
from the moment a frame is sent until the echo has been
received correctly.
Segmentation
If an echo monitoring error or a frame falsification arises
at an optical port, the module assumes that the line is
faulty and blocks this port for user data. The connected
field bus partial network is then segmented (cut off). This
segmentation causes the module at the other end of the
optical fiber to be segmented as well.
Both modules connected to the segmented field bus
partial network send test frames to the segmented ports.
These test frames – which are to be received regularly –
can be used by both modules to check the status of the
field bus partial network.
The segmentation is automatically lifted as soon as the
test frames indicate to both modules that the segmented
field bus partial network is no longer disturbed.
If all active bus subscribers are deactivated in a previously
active network, the modules are segmented cyclically in
order to check the fiber links to the neighboring modules.
If there is no frame traffic, but the fiber links are intact,
the port LEDs of the optical ports flash yellow cyclically.
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