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Notes:


The starting and ending address of each memory chip is shown above. We can see that
ROM 0 chip should be enabled when bit 14 is 0 and bit 13 is 0 (number 00);
ROM 1 chip should be enabled when bit 14 is 0 and bit 13 is 1 (number 01);
ROM 2 chip should be enabled when bit 14 is 1 and bit 13 is 0 (number 10);
ROM 3 chip should be enabled when bit 14 is 1 and bit 13 is 1 (number 11);

Address bit 15 for all chips is 1.

Therefore we can use a decoder chip to implement the address decoding circuit. The input of the decoder is A13 and A14. A15 is connected to chip enable of the decoder. The output of the decoder is the chip select signal.