Siemens SIMATIC PCS 7 Operating Manual page 99

Note
If the R_ID is not an uneven number, the following error message will appear when the
CFC charts are compiled:
"Module/connection with address/R_ID 16#0002/16#00000004 is being used by more
than one block. [Assign a module/connection with this address/R_ID to no more than one
block and use only uneven R_IDs.]"
5. Interconnect the ACK_REQ outputs of the F_RCVBO, F_RCVR, or F_RDS_BO F-blocks
to ascertain whether acknowledgment is required on reintegration following
communication error elimination.
6. Interconnect the relevant ACK_REI inputs of the F_RCVBO, F_RCVR, or F_RDS_BO F-
blocks with the signal for reintegration.
Note
If the S7 connections between the automation systems have been changed, the safety
program will need to be recompiled.
User acknowledgment is always required for reintegration following PROFIsafe
communication errors (ACK_REQ output set).
7. Configure the TIMEOUT inputs of the send and receive blocks with the same calculated
timeout value.
8. Configure the receive block substitute values for the scenario of a communication fault.
Communication is established internally in both directions (sending and receiving) for the F-
communication. Keep in the mind the maximum communication load of the AS.
If the maximum communications load of a system is 100 requests per second, for example,
this results in a total of 20 communications requests with 5 F_RECVX and 5 F_SENDX-B
blocks. If these are configured in OB 37 (1 s), this corresponds to a communication load of
20%. These blocks, which are integrated into OB 38 (300 ms), correspond to a
communication load of 66%.
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB
Configuring the safety program
7.3 Configuring fail-safe AS-AS communication
99