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If you know how to connect one 64kB Eprom to 8051 then connecting more 64kB memory banks should not be a problem for you ..
512kB -> 8 banks of 64kB
1MB --> 2 x 512kB --> 2 x (8x64kB) ..
Connect the following:
P1.0 to A16
P1.1 to A17
P1.2 to A18 .. and so on ..
When any of the control bits, P1.0, P1.1, .., are changed from 1->0 or 0->1 the processor begins to fetch instructions from the other 64kB bank at the address of the next instruction after the instruction that initiates the bank switch ..
Use combination of ANL P1, #111XXXXXb and ORL P1, #000XXXXXb to change banks ..