Mad-1 decoder questions and wiring

Hello there! I have done som repros Before but this time i have to fit 2 eeproms on one cart.
Im using simcity as donor its an lorom cart with 256kb save ,but it has only Place for one eeprom.
there is also one mad-1 decoder chip on the cart. How shall i wire the second eeprom?

Please help me...


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According to this: you need a 74hct139
https://drive.google.com/file/d/0B9MtAZ ... ZFTmc/view


edit: well that is for eprom, just noticed you are doing eeprom not sure if it is the same.

You don't need the extra '139 decoder, MAD-1 can address two ROMs.

http://wiki.superfamicom.org/snes/show/ ... nd+Pinouts
^Scroll down to MAD-1 pinout.

If there's only one mask ROM then OE will be connected to MAD-1 pin 4. If there's two mask ROMs, then ROM1 OE will connect to MAD-1 pin 16 and ROM2 OE will connect to MAD-1 pin 1 (MAD-1 pin 4 will be NC in this case). IIRC all the pins of the mask ROM are connected in parallel with the exception of OE.