well, the memory address that holds the region setting (jap,asia/eur,us) is 0x10FD83.
The main 68k memory is mapped 0x100000-0x10FFFF. It is held as a UINT16, so you
must byteswap the data (and the address and divide it by 2).
The program expects that the data read from 0xFFFFE will include 0xFFFFF (68k instuctions are 2 bytes),
and is byteswapped, so you would return 0xFF01 or 0xFF00.
The reason that I did this +1)>>1 is because Japan is 0x00 in the main ram, asia/us is 01 or 02
and this was the shortest way to make 02->01 and 01->01 and 00->00.
the 0xFF00| is to make sure it returns 0xFF01 or 0xFF00.