Use the Change To Read and Change To Write shortcut menu items to change a read global to a write global or vice versa. Doing this changes the data direction of the global variable.
Complete the following steps to change the configuration of a global variable so that it acts as a read global and then change it back to a write global.
Select Functions»Structures»Global Variable to place a global variable node on the block diagram.
Right-click the global variable node and select Change To Read from the shortcut menu to configure the global variable to work as a control. The global variable changes to a read global and has a thick border.
Right-click the global variable node again and select Change To Write from the shortcut menu to make the variable a write global.