ERPC functions
6.2 ERPC services and communication
CP 343-1 ERPC
44 Manual, 03/2010, C79000-G8976-C239-02
Assignment of the logical triggers
The assignment of the logical triggers to the following relevant data on the S7 station is
made in the ILS Workbench:
● Logical trigger - Data areas of the CPU (ERPC symbols)
● Logical trigger - configuration DB
To complete the ILS Workbench configuration, you will need to connect the CP on which you
have loaded the STEP 7 configuration data to the host of the ILS Workbench via Ethernet.
The ILS Workbench then reads the configured ERPC symbols and the characteristic data of
the configured configuration DB from the CP.
Following this, you can make the assignment of the logical triggers to the ERPC symbols
and the configuration DBs in the ILS Workbench.
6.2.5 ERPC communication between CP and CPU
Addressing the CPU data areas
The CPU data areas used for ERPC communication can be either data blocks (DBs) or bit
memory areas. They are addressed either directly or via symbols. As normal in STEP 7,
symbolic addressing is defined in the symbol table of the CPU. The advantage of symbols is
that as well as having an address and size information, they also have a meaningful name
that might, for example, indicate the technical function in the process. Address changes due
to modifications to the program are also easy to update by downloading the symbol table or
the ERPC symbols to the S7 station.
On the CP 343-1 ERPC, the symbols used for ERPC communication are known as "ERPC
symbols". These need to be transferred to the CP firmware to ensure consistency with the
ILS Workbench configuration. Once the required symbols have been defined in the symbol
table of the CPU, they are specified and configured as ERPC symbols in the properties
dialog of the CP in STEP 7.
NOTICE
Special case "DB with structure"
A data block with structures (array with complex S7 data types) cannot be addressed using
symbols. This type of CPU data area needs to be addressed directly.
Job size and data consistency
Note
Data can originate from different read jobs.
With read jobs of the ERPC application larger than 210 bytes, data is returned from the S7-
CPU that originates from more than one read job by the CP.
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