A network of processing units having at least one switch that allows disruption of the network between a first and a second processing units is provided. Disruption of the network by means of the switch effectively disconnects the first processing unit from the network and couples the first processing unit to a controller of the network. The controller is adapted to exchange data with the disconnected processing unit and thereby allows selective and direct data exchange with a selected processing unit. In particular, in the framework of heterogeneous and hierarchical networks of processing units, the switch techniques provide direct access to processing units and sub-networks and allow for an efficient and fast performance of diagnostic and maintenance procedures of sub-networks and their corresponding processing units, such as performing a flashing procedure.