Configuring Symbol File (PacDrive M) - General Information
Communication between the PacDrive M controller and the OPC server is performed via the gateway server V2. The OPC server receives the information via the OPC items (variables) available in the symbol file. The symbol file is created by EPAS-4 when building a project and is stored in the project directory. To achieve this, select the option Generate symbol entries in EPAS-4, Project > Options, category Symbol Configuration.
NOTE: If the option Create system entries is activated, the symbol file is created when the project is built. As a result, the built process takes longer. The symbol file is available to the OPC server or gateway server after it has been downloaded to the controller.
NOTE: Make sure that in EPAS-4 the presetting for transferring the symbol file is selected.
You can modify this setting by selecting the check box Update Symbolfile in the Project > Options > Login dialog box.
NOTE: If the project is redownloaded to the controller without changing any symbols, it may happen that an empty symbol file is transferred. Thus, no symbols can be displayed via the OPC server.
To help to prevent this, you can insert a dummy variable that can be removed at a later point in time.
NOTE: Assign individual project names and symbol file names to the different controllers to help to differentiate them.
NOTE: The symbol file should only contain symbols that are required for one visualization. A slim symbol file has a positive effect on the performance of the OPC server.
Configuring the Size of the Symbol File
You can configure the size of the symbol file in EPAS-4 by executing the command Project > Options. In the Symbol configuration dialog box, click the button Configure symbol file....
In the symbol file configuration dialog box, you can select the following entries for each individual object:
|
Designation |
Description |
|---|---|
|
Display the object variables |
The variables of the selected objects are added to the symbol file. |
|
Display collective entries |
For arrays and structures, an object is created in the symbol file. This allows, for example, the entire array to be addressed via one object in a visualization. The setting depends on output structure components and output field components. NOTE: Many visualizations do not support collective entries of fields and structures. |
|
Display the structure components |
Structures (STRUCT) are added to the symbol file. NOTE: Collective entries of structures are treated as BYTE-ARRAY. The OPC server is only provided the size of the variables. Access to the structure components must be triggered by the client. To do so, it is necessary for the client to be familiar with the structure setup. In practice, structures are not used as collective entries for the OPC server. |
|
Display the field components |
Fields (ARRAY) are added to the symbol file. |
|
Write access |
Write access to variables can be locked. NOTE: Confirm every modification for one or several objects in the dialog box Set object attributes by clicking the OK button. |
It is a good practice to define the variables which the OPC server is to access in a global variable list and to add this global variable list to the symbol file generation in the symbol configuration of EPAS-4.
This reduces the content of the symbol file to the necessary symbols and thus the file size remains small. Resource consumption is kept to a minimum.
If variables of functions and function blocks are not available in the symbol file, verify the following:
oFunctions do not have a memory area.
oFunction blocks have a memory area. Decide from which of the n instances the variables should be transferred to the symbol file
