Can I change the EUI64 used by an Ember radio?

See this introduction to addresses in ZigBee for more background information.

Each EM250 and EM260 is programmed by Ember with one of Ember’s IEEE EUI64 addresses.  This is programmed into the manufacturing section of the chip’s flash and can not be erased or altered. 

Customers can use the Ember pre-programmed EUI64 for their products, or they may also choose to use their own block of IEEE address, in which case they will need to program their EUI64 during product manufacturing. This does not overwrite the Ember EUI64 but it does configure the chip to use the one supplied during manufacturing.

The procedure for programming a custom EUI64 can be found in App Note “Bringing up custom devices – 120-5031”