A system includes a well tool for deployment in a well, a controller, and a link coupled between the controller and the well tool. The well tool comprises plural control units, each of the plural control units having a microprocessor and an initiator coupled to the microprocessor. Each microprocessor is adapted to communicate bi-directionally with the controller. The controller is adapted to send a plurality of activation commands to respective microprocessors to activate the respective control units. Each activation command containing a unique identifier corresponding to a respective control unit.