Network component Bus system Application
AFD (Automatic Field Dis‐
tributor)
AFDiSD
Fieldbus
● PROFIBUS PA
● FOUNDATION
Fieldbus
Connection of field devices via ring redundancy
● Maximum of 31 fieldbus components on one
bus
● Maximum of 8 AFD/ADFiSD on a redundant
bus link
● Maximum of 4 field devices per AFD
● Maximum of 6 field devices per AFDiSD
AFS (Automatic Field Split‐
ter)
Fieldbus
● PROFIBUS PA
● FOUNDATION
Fieldbus
Connection of field devices via coupler redun‐
dancy
● 1 AFS on a redundant bus link
● Up to 31 fieldbus components on the AFS
Redundancy manager
Certain network components in the SIMATIC NET product range support the redundancy
manager function.
This function enables the configuration of ring redundancy. Network components operating as
the redundancy manager can ensure that the bus connections remain undisturbed if there is
a fault on a bus line (such as a cable break).
Example of a ring structure with SCALANCE X400 and X200
The SCALANCE X414-3E as the redundancy manager has a gray background in the figure.
Standby manager
Switches and data links (network cable) connect the redundant networks. Redundant coupling
of networks is only possible if two devices (switches) within a network segment support the
standby manager function. Certain network components from the SIMATIC NET product range
support this function.
Within a network segment, both devices are configured for the standby manager function. The
two devices exchange data frames via the bus line and thereby synchronize their operating
status. One network component becomes the standby manager (master) and the other standby
manager (slave).
When operation is error-free, the data link running between the redundant networks is active
for the standby manager (master). If this data link fails (e.g., due to a defective device or cable
break), the standby manager (slave) activates its data link while the fault remains pending.
Example of a ring structure with SCALANCE switches
High availability solutions in PCS 7
4.3 Solutions for communication
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA 57
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