Gameboy Development Forum

Hi!
I'm working in a Flash Cart as you can see in this thread: http://gameboygenius.8bitcollective.com … .php?id=38
Now i'm thinking on adding features to it, like 128K Save RAM (planned) and an interface to access external hardware.

So i'm thinking on a way to use the cart bus to write/read data to/from something different than the ROM and SRAM.
As my cart uses MBC5, If address A000 (normally used to access cart RAM) is used, the ROM is disabled (as ROM /CS is connected to A15), but to enable the cart's RAM, you have first to write 0Ah to 0000-1FFF.

So, if I write/read from A000 without enabling cart's RAM, I think I can access some external interface, do you think I'm right?
I'm thinking on NANDing A15 and Cart's RAM /CS to obtain a /CS signal to this interface. (if sram and rom are disabled, external stuff is enabled).

What do you think about this?

Tnks.