Now the bootloder region starts at 0x00 and goes up to 0x2000 (8kB).
The application code begins at 0x2000 and ends at 0x10000 (56kB).
There's also a spare region in the last 2 sectors from 0x10000 to
0x11FFF reserved for firmware upgrade.
The last word of the application areas (upgrade and active) is the
firmware id.