I/O System S900
Communication Interface for PROFIBUS DP, CI920
3BDD010422R0101 33
• the PROFIBUS communication of the active CI920 fails longer than 15 s.
This operating mode features the following restriction:
• No diagnostics of the redundant PROFIBUS line.
Redundancy Mode "1"
In redundancy operating mode LR_MODE1 a certain behavior of the master
is assumed, in order to be able to diagnose all failures of the PROFIBUS
lines. The redundant CI920 becomes active when
• the active CI920 is removed, or
• the PROFIBUS communication of the active CI920 fails.
This redundancy operating mode features the following characteristics:
• Monitoring the active PROFIBUS connection in transmit and receive
direction
• Diagnosing the redundant PROFIBUS connection in transmit and receive
direction
• No additional engineering requirements,
• No additional bus load.
Prerequisites
• The CI920 must be parameterized accordingly for redundancy.
• The address of the passive CI920 must be a vacant node address.
• The PROFIBUS master must poll the passive CI920 (FDL status polling).
• Alternatively a minimum configuration can be set up for each passive
CI920. This is optional and facilitates the diagnostics in the control
system. The configuration is limited to a CI920 user data (CIPB C), so
that the bus load does not increase drastically.
• Both PROFIBUS lines must be sufficiently isolated.
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