Object ‘Persistent Variable List’¶

Symbol:

This object is for the management of persistent variables.

The persistence editor automatically manages the order of the persistent variables. It allows the addition and deletion of persistent variables without loss of data - independent of their position in the declaration:

If the user deletes a variable from the declaration, CODESYS automatically replaces the variable by an invisible placeholder variable in the process image. This placeholder has the same size as the deleted variable and thus guarantees that the following variables retain their addresses. If you add a new variable at any position, this is appended to the process image at the end, so that existing variables also retain their addresses. The changing of variables (name or data type) is treated like a deletion and a new creation and thus creates a gap or a new entry at the end of the process image (not in the declaration). The addition of variables from programs or function block instances using the command Add all instance paths takes place in the same way. The persistence editor also offers commands for the determination of the number of gaps, for cleaning these gaps and for backing up and restoring the persistent values with the help of recipes.

See also

• Data Persistence
• Remanent Variables - RETAIN, PERSISTENT
• Command ‘Save Current Values to Recipe’
• Command ‘Reorder List and Clean Gaps’
• Command ‘Restore Values from Recipe’
• Command ‘Add all Instance Paths’