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Entry type: FAQ, Entry ID: 17413251, Entry date: 11/10/2008

How do you use the variable symbols defined in STEP 7 with the OPC server of SIMATIC NET?

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Configuration notes:
In version V6.1 of SIMATIC NET (CD 11/2002) and higher you can use the symbol table and the data block symbols of your STEP 7 project as a basis for generating the symbols of the SIMATIC NET OPC server.

This entry describes how to generate symbols for the SIMATIC NET OPC server from the STEP 7 symbol table.

A PC station with a standard Ethernet network card is used. Data exchange between PC station and S7 station is implemented via Industrial Ethernet using S7 Communication.

Both PC station and S7 station must be configured in the same STEP 7 project.

Configuration of the S7 station:
Use the SIMATIC Manager to open your STEP 7 project that contains the SIMATIC S7 station.

Fig. 01: STEP 7 project

Switch to the S7 program folder and double-click on "Symbols". The symbol table opens.

In the symbol table you define the symbol names you want.

Fig. 02: Symbols in the symbol table

Other variables with symbol names of the STEP 7 project are in the existing data blocks - DB1 in this example.

Fig. 03: Variables in DB1

Download the hardware configuration and the user program to the CPU of your S7 station.

Configuring the PC station:
You insert a new PC station via the menu Insert -> Station -> SIMATIC PC Station.

Fig. 04: Inserting a PC Station

Please follow the instructions given in Entry ID 15355168 for configuring the PC station.

Incorporating STEP 7 symbols in the OPC server:
Then right-click the OPC server and open the Object Properties of the OPC server.

Fig. 05: Opening the Object Properties of the OPC server

In the Properties dialog of the OPC server you switch to the "S7" tab. In this dialog you define which STEP 7 symbols are used in the OPC server. Enable either the "All" or the "Configured" option.

Fig. 06: Properties dialog of the OPC server - "S7" tab

If you enable the "Configured" option, then you right-click the "Configure..." button. The following dialog opens.

Fig. 07: Configure Symbols dialog - variable symbols in the symbol table

Fig. 08: Configure Symbols dialog - variable symbols in the data block

In the "Configure Symbol" dialog you can make the variable symbols defined in the symbol table and data block visible for the OPC server and define their authorization (Read/Write, Read, Write or none).

Click the "OK" button to close the "Configure Symbols" dialog.

Then, in NetPro, you mark the PC station and save and compile the complete configuration.

Fig. 09: Saving and compiling the configuration

Mark your PC station.

Fig. 10: Save and Compile

If warnings are displayed when saving and compiling the configuration, then they should be treated as purely information. It is possible to download the configuration into the PC station. If errors occur when saving and compiling, it is not possible to download the configuration into the PC station.

In NetPro, you mark the PC station and click on the "Download" button to download the configuration into the PC station.

The following message reminds you that the downloading procedure will delete the data already on the components concerned and the new data will be downloaded to them.

Fig. 11: PLC download

Acknowledge the message with "OK". Now the download starts.
First the target modules are stopped. Acknowledge the subsequent message with "OK" to continue the download procedure.

Fig. 12: Stopping the target modules

The following entry provides information on possible causes of error messages during the downloading procedure 12033912.

Successful downloading completes configuration of the PC station.

Use the OPC Scout to check whether the STEP 7 symbols are available in the OPC server. This OPC client is included in the SIMATIC NET PC software.

Start the OPC Scout in the Windows START menu via SIMATIC -> SIMATIC NET -> OPC Scout.

Double-click on "OPC.SimaticNET" to connect to the SIMATIC NET OPC server.

Fig. 13: Connecting to the SIMATIC NET OPC server

In the dialog box that opens you enter a group name of your choice.

Fig. 14: Entering a group name

Double-click on the group name created, "S7" in this example, to open the OPC Navigator. In the OPC Navigator you can define the OPC items.

Fig. 15: Opening the OPC Navigator

The incorporated STEP 7 symbols are to be found in the OPC Navigator in the "...\SYM" folder.
Double-click on "\SYM". The S7 station from the STEP 7 project is displayed. This contains more subfolders (CPU and data blocks).
The variable symbols that you defined in the STEP 7 symbol table are contained in the CPU folder. Mark the CPU folder. The defined variable symbols are displayed in the middle window pane. Mark the variable names and click on the "->" button to add them to the OPC item list. Click "OK" to close the dialog. 

The variable symbols defined in the data block are in the data block folder.

Fig. 16: OPC Navigator

The OPC Scout has added the selected variables with symbolic names to the list of OPC items.
If the quality of the OPC items is good, then the communication connection can be set up and you can read/write the values of the OPC items.

Fig. 17: List of OPC items

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