When working with shared data blocks in a programming environment, it's essential to understand how to define and manage their structure. If you open a data block that is not assigned to a user-defined data type (UDT) or a function block (FB), you can define its structure directly in the declaration view of the data block. However, for unshared data blocks, this view cannot be modified once it's set.
For shared data blocks, which are not linked to any UDT or FB, the declaration view is automatically displayed if no other view has been selected. You can then fill out the form to define the data structure based on the information provided. Keep in mind that unshared data blocks do not allow changes to their declaration view.
When a data block is associated with a function block (often referred to as a background DB), the variable declarations within the function block determine the structure of the data block. Any modifications must be made within the function block itself. To do this, open the relevant FB, edit its variable declarations, and recreate the instance data block. The declaration view will then show how variables are defined in the function block.
When working with user-defined data types (UDTs), the structure is defined by specifying the order of variables, their data types, and initial values. If the view hasn't been set, the claim view is shown by default. You can input variable names using the TAB key or Enter, and the system will validate the entries as you go.
Once a data block is assigned to a UDT, the structure of the UDT dictates the layout of the data block. Any changes must be made within the UDT itself. After editing the UDT, recreate the data block to see the updated structure in the declaration view.
In the data view, you can only modify actual values. Use the menu command "View > Data View" to switch to table display mode. Enter the required value into the "Actual Value" column, ensuring it matches the data type of the element. Incorrect entries will be highlighted in red and must be fixed before saving.
To reset values to their initial state, use the "Edit > Initialize Data Block" command. This will overwrite all current values with the predefined initial values. Always check for syntax errors before saving. These errors appear in red during editing and must be resolved before the block can be saved.
When saving data blocks, ensure they are stored correctly on the programming device’s hard drive. Use "File > Save" to save under the same name or "File > Save As" to choose a new name or path. Note that for data blocks, some names like DB0 may be reserved for system use. Make sure there are no syntax issues before saving.
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