Harish

7FFF in binary is 0111 1111 1111 1111
8000 in binary is 1000 0000 0000 0000

then for 0000 to 7fff the MSB bit is zero and
for 8000 to ffff the msb bit is one

take the MSB put in an input of an nand gate, and the other input to zero logic then put input and output to a poles of DPDT switch and the poles switched to CS of the eprom and ram

in –> nand -> dpdt (pole 1 and 4)
in -> dpdt (pole 2 and 3)

dpdt (pole 5 –out-) to CS ram
dpdt (pole 6 –out-) to CS eprom

then you can select easily what range is asigned

sorry for my english.

Regards,

Ricardo