Installation
2
0
1
8
-1
2
53
3.13.2
Media Redundancy
Media redundancy is when the master communicates with a com unit via a voter and a
redundant fieldbus cable. The com unit that communicates with the master is active and
controls the I/O module on the backplane. The second com unit is passive and reads the data
traffic on the backplane.
If the active com unit fails, the passive com unit automatically takes on the configuration of the
com unit that was previously active. When there is media redundancy, switching between the
com units is independent of the fieldbus cable used.
Figure 3.23
Line redundancy
If the master is also redundant, this is known as extended media redundancy.
Figure 3.24
Extended media redundancy
3.13.3
Application Redundancy
In application redundancy, the master has two redundant interfaces to allow it to access both
the fieldbus and the redundant fieldbus. Both com units are active on both fieldbuses.
However, internally only one com unit is active and controls the I/O modules.
If a fieldbus cable or a com unit fails, a switchover to the redundant fieldbus cable will take
place. In the case of application redundancy, the switchover makes the redundant fieldbus
cable the active fieldbus cable, and all com units on this fieldbus cable become active com
units.
Redundant
Fieldbus
Voter
Master
Fieldbus
Backplane
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Voter
Red.
Master
Redundant
Fieldbus
Voter
Master
Fieldbus
Backplane
C
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it
R
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C
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it
Red.
Master
Redundant
Fieldbus
Master
Fieldbus
Backplane
C
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U
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it
R
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