Each variable has an attribute displayed in the corresponding column of the grid. Physical I/Os are marked as either Input or Output. Inputs are read-only variables. For each internal variable, you can select the Read Only. Otherwise, the attribute column of an internal variable is empty. Parameters of User Defined Function Blocks are marked as either IN or OUT.

To change the attribute of an internal variable, enable the modification mode in the grid and move the cursor to the selected attribute cell. Then press ENTER to set or reset the Read Only attribute.

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