ERPC functions
6.2 ERPC services and communication
CP 343-1 ERPC
Manual, 03/2010, C79000-G8976-C239-02
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6.2 ERPC services and communication
6.2.1 Communication between S7 station and ERP subscriber
Methods of data transfer
Two methods are available for data transfer:
● Read and write jobs
These are spontaneous or cyclic read and write jobs to the S7 station.
– Cyclic read/write jobs are configured in the Workbench and downloaded to the CP via
the ILS-Workbench configuration.
– Spontaneous read/write jobs are initiated by the Workbench.
● Event-oriented data transmission with the logical trigger
The event-oriented transmission of data from the process is started with help of a "logical
trigger" on the S7-CPU. When the logical trigger is fired, the values of the configured data
areas are transferred from the CPU to the ERPC application on the CP for forwarding to
the ERP subscriber.
The logical trigger can also be configured so that data is requested from the ERP
subscriber and is then written to the CPU using a standard write job (see " Read and
write jobs").
The frame buffer
If an ERP subscriber is unreachable, the frames intended for it are stored temporarily in a
frame buffer of the CP (store-and-forward mode).
If the ERP subscriber is unreachable, the requested frames are buffered on the CP until the
subscriber can be reached or the frame buffer overflows.
If the ERP subscriber is still unreachable after the maximum memory capacity had been
used up, data is lost.
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