Siemens SIMATIC S7 F Manual page 134

Programming
Communication Between Run-Time Groups or CPUs
You must proceed in several steps if the communication is to continue in all
phases. In one step, only the change for one communication partner can be
introduced. Changes must not be downloaded for both partners simultaneously.
•
Inserting new F-Blocks for communication between run-time groups: Substitute
values are output until the newly created connections are synchronized.
The sending side must always be programmed and downloaded first.
The receiving block can be placed and immediately interconnected with the
send block only as of the second step.
•
The data sources and sinks can be changed (i.e. the interconnections from/to
the output/input parameters of the blocks). Such a change should, however,
never be made for a data value at the same time for the sender and the
receiver because simultaneous activation of the new interconnections cannot
be guaranteed. If it is absolutely necessary, proceed as follows:
- On the sending side, attach the desired interconnection to a new,
previously unused input parameter of the end block and download this
change. The new value at the receiver is now correctly available.
- In the next step, the new interconnection on the receiver side can be made
using the new output parameter of the receiving block rather than the old
one as the source. This change can be downloaded and results in a
consistent switch to the new data paths.
- Finally, the now superfluous interconnection to the old input parameter of
the send block can be deleted on the sending side.
•
The situation is particularly crucial if a communication partner is replaced, i.e. if
communication is supposed to go to another run-time group or to another CPU.
This is only possible if a second channel is set up for the new communication
partner and a switchover is then made to it. This applies when data is to be
received from a different CPU than before. However, the principle is just as
valid for communication between run-time groups.
- Configure the new connection in NetPro and download the connection data
in RUN mode (this step is required only for CPU-CPU communication)
- Place new communication blocks on the sending side and assign the data
of the new connection (ID, R_ID). Interconnect, compile and download the
data to be sent to the send block.
- Place new communication blocks on the receiving side, assign the data of
the new connection (ID, R_ID), and then compile and download them. The
data of the old and new sender is now available in the receiver.
- The interconnections can now be switched over from the old to the new
receive block and the old receive block can be deleted. When the changed
program is downloaded, a switchover immediately takes place to the new
sender.
- Finally, the now superfluous send block of the old sender can be deleted
and perhaps also the corresponding connection from NetPro.
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Fail-Safe Systems
A5E00085588-03