Siemens SIMATIC PCS 7 Function Manual page 69

Fault-tolerant communication solutions
The following communication solutions are offered to prevent a possible failure:
● Ring redundancy with the AFD (Active Field Distributor)
● Coupler redundancy with the AFS (Active Field Splitter)
The DP/PA coupler can be used stand-alone or in the DP/PA-Link .
Note
Mixed configurations
You can connect only one redundant DP/PA coupler pair per DP/PA-Link . In mixed
configurations, you can operate up to 3 additional non-redundant DP/PA couplers. The
coupler pair (FDC 157-0 DP/PA coupler) should be installed for redundant operation in the
last two slots of the ET 200 station.
Connecting the fault-tolerant PROFIBUS PA to PROFIBUS DP
You can connect a fault-tolerant PROFIBUS PA to the PROFIBUS DP. The following variants
can be realized:
● Connection to a redundant PROFIBUS DP
● Connection to a singular PROFIBUS DP
We recommend the following configuration limits in PCS 7 when connecting PA devices using
AFD or AFS :
● For the purpose of increasing availability when using ring redundancy (fault-tolerant
● Connect an active field splitter (AFS) to a redundant coupler in the case of coupler
● You can connect a maximum of 31 field devices per PROFIBUS PA.
● The maximum power consumption of 1 A must not be exceeded. This figure includes all
Fault-tolerant Process Control Systems (V8.0)
Function Manual, 03/2012, A5E02779471-02
– Connection of a fault-tolerant PROFIBUS PA via redundant DP/PA-Link
(2 x interface module and 2 x DP/PA coupler)
– Connection of a fault-tolerant PROFIBUS PA via DP/PA-Link with redundant coupler
pair (1 x interface module and 2 x DP/PA coupler)
– Connection of a fault-tolerant PROFIBUS PA with redundant FDC 157 coupler pair
(2 x DP/PA coupler directly on the PROFIBUS DP)
connection), connect a maximum of 4 field devices (one field device per spur line) to an
active field distributor AFD (maximum of 8 AFD to a redundant DP/PA coupler). You can
connect a total of 31 field devices.
redundancy. Connect the field devices via AFD (max. 8 AFD). For the purpose of increasing
availability, connect a maximum of 4 field devices per AFD.
components connected to the PROFIBUS PA.
Fault-tolerant Solutions in PCS 7
3.3 Solutions for communication
69