One way is to use Analog Devices' DS2401. This product uses the 1-Wire® interface to easily add a unique address to any board or system. The part has a unique 64-bit serial ID (48 bit serial number, 8-bit family code and a 8-bit CRC) that allows over 280 billion addresses to be created. In addition, the DS2401 gets powered from the interface using an internal parasite power circuit.