fox niner, here is the extract from the FCOM
A pilot can deactivate the other stick and take full control by pressing and keeping pressed his priority takeover pushbutton.
For latching the priority condition, it is recommended to press the takeover push button for more than 40 s.
This allows the pilot to release his takeover push button without losing priority.
However, a pilot can at any time reactivate a deactivated stick by momentarily pressing the takeover push button on either stick.
If both pilots press their takeover pushbuttons, the pilot that presses last gets priority.
Hope that helps.