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ERPC functions

6.2 ERPC services and communication

CP 343-1 ERPC

Manual, 03/2010, C79000-G8976-C239-02

● In the CPU, apart from the logical trigger, you can also see the variables that define the

readable/writable data areas in the form of configurable ERPC symbols. No resources

are required on the CPU for read and write jobs from the application.

The "ILS Workbench" for configuring the ERPC application and "STEP 7" for configuring the

SIMATIC station are shown among the configuration tools.

6.2.3 Reading and writing data

Types of read/write jobs

To allow the ERPC application to read or write data, the following options are available:

● Reading from the CPU

– Cyclic reading from the CPU

Following a read job, data is read cyclically from the CPU by the CP and sent to the

ERP subscriber.

– Spontaneous reading from the CPU

Following a single read job from the ERP application, data is read once from the CPU

by the CP and sent to the ERP subscriber.

● Writing to the CPU

– Spontaneous writing to the CPU

The data from the ERP subscriber is written to the CPU once a following a write job.

If data is requested from a logical trigger by the ERP subscriber, this is written to the

CPU using a write job.

Sequence of read and write jobs

If it is problem free, a read/write job from the ERP application is executed in the following

steps:

1. The ERPC application initiates a cyclic read/write job.

For test purposes, the ERPC application on the CP can also accept a spontaneous

read/write job from the ILS Workbench.

2. The CP starts the read/write service with which the values are written to the CPU or read

from the CPU and sent to the CP.

Depending on the size of the data, one or more read/write jobs are sent. With a read task

for which more than one read job is necessary, the CP waits until the last read job is

completed.

3. Once the read jobs have been completed and the data of the read task is complete, the

ERPC application sends the requested data frame to the ERP subscriber.

4. If the ERP subscriber is unreachable, the data frame is stored on the CP.

If an error occurs, and error identified is returned and a diagnostic message is entered in the

diagnostic buffer of the CP.

Siemens SIMATIC NET CP 343-1 ERPC User Manual

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