How does the cartridge slot get mapped to 0x400000?

For anything related to cart (SRAM, SF2 mapper, audio, CD mode 1, ...)

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Mechanical Menace
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How does the cartridge slot get mapped to 0x400000?

Post by Mechanical Menace » 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.

notaz
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Post by notaz » 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.

Mechanical Menace
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Post by Mechanical Menace » Mon Apr 07, 2014 2:10 pm

Thanks, that has helped a few things make more sense.

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db-electronics
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Post by db-electronics » 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.
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