A first slave electronic module and a second slave electronic module are adapted for communicating over the data bus. The first slave electronic module has a first resistor coupled in series with a main power line. The second electronic module has a second resistor coupled in series with the main power line. A master electronic module has a master current measurement circuit for determining an aggregate current level indicative of the total number of slave electronic modules on the main power line. A first current measurement circuits is capable of measuring a node current indicative of a number of other active slaves connected to the main power line and data bus. A master data processor in the master electronic module is arranged to assign a unique module identifier to a first slave electronic module based on the first node current and the aggregate current level, the unique module identifier indicating a respective position of the first slave electronic module on the data bus.