A UART boot loader is pre-loaded on the AT32UC3L064. To enter this boot loader mode, the WAKE pushbutton must be pressed upon reset and then released. It is then possible to program the AT32UC3L064 through the UART boot loader. Note also that if the AT32UC3B1256 is running the pre-loaded virtual com port firmware, it is possible to program the AT32UC3L064 with the UART boot loader through the USB. For detailed information on the AVR UC3 UART boot loader, check Reference Materials.