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How does the cartridge slot get mapped to 0x400000?
Posted: Mon Apr 07, 2014 11:51 am
Is it something the MD does automatically when the expansion port is used and the cartridge detect pin is low or does the CD bios do it?
Sorry if this is a stupid question.
Posted: Mon Apr 07, 2014 12:17 pm
It's controlled by /CART (B32) pin on the cart connector only, if it's connected to ground, cart's /CE (chip enable) signal will respond to 000000-3fffff, else to 400000-7fffff.
Posted: Mon Apr 07, 2014 2:10 pm
Thanks, that has helped a few things make more sense.
Posted: Tue Mar 03, 2015 1:12 pm
Now that I think of it, smart address decoding coupled with selective driving of #CART is almost certainly how the Everdrive can loads a CD BIOS from the cartridge port.