Siemens SIMATIC PCS 7 Function Manual page 124

Advantages of fault-tolerant components
4.3 Communication connections
Hardware setting on the DP/PA coupler
Note
The redundancy mode set on the DP/PA coupler (DIL switch bit 7) must match the configured
redundancy mode:
● OFF: coupler redundancy (default setting)
● ON: ring redundancy (line redundancy)
If there is a discrepancy between the set redundancy mode and the configured redundancy
mode, a diagnostic message is generated.
Procedure
1. In the component view, select the SIMATIC H station and double-click the "Hardware"
object in the detail window.
HW Config opens.
2. If the hardware catalog is not visible, select the menu command View > Catalog.
The hardware catalog opens.
3. In the current PCS 7 profile, double-click "PROFIBUS DP" and then "DP/PA Link".
4. Select the FDC 157-0 DP/PA coupler and drag it onto one of the two PROFIBUS DP lines.
5. Select shortcut menu command Object Properties.
The "Properties - DP Slave" dialog box opens.
6. Click "PROFIBUS".
7. Enter the PROFIBUS address (PROFIBUS DP) in the "Properties - PROFIBUS Interface
FDC 157-0" dialog box and click "OK".
The "Properties - PROFIBUS" dialog box opens.
8. Open the "Network Settings" tab.
9. Select the "User-defined" item in the "Profile" list.
10.Click "Bus parameters...".
11.Ensure the value 3 is set for the "Retry Limit" parameter.
12.Click "OK" in the dialog boxes that were opened for this procedure.
13.Repeat steps 1 to 13 for the second DP/PA coupler for coupler redundancy.
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Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA