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How to connect an external ROM over 4MB at the invalid extension of ROM?

Latest Updated:04/23/2009

Question:

Please advise me how to connect an external ROM over 4MB at the invalid extension mode of embedded ROM.

Answer:

Address A23 ~ A21 can't be outputed since PF7/A23(5pin) ~ PF5/A21(7pin) are set at input port right after reset. Please don't use the address at A23 ~ A21="1"(Hi) in the reset vector and add pull down resistors at A23 ~ 21 address pin s on a board.
Suitable Products
H8SX/1600
H8SX/1663
H8SX/1657
H8SX/1650, H8SX/1651
H8SX/1648A, H8SX/1648L
H8SX/1638, H8SX/1638L
H8SX/1622