Acorn Atom and AtoMMC

discussion of games, software, hardware & emulators relating to the Acorn Atom
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Acorn Atom and AtoMMC

Post by RTB » Tue Jul 10, 2018 3:57 pm


I have an Acorn Atom which has the BBC Basic board fitted.

I just wanted to check if anyone knows of any compatibiity problems if I were to add an AtoMMC alongside this board?

Thanks for your help
BBC board.jpeg

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Re: Acorn Atom and AtoMMC

Post by oss003 » Tue Jul 10, 2018 6:22 pm

Hello RTB,

in a standard Atom, the AtoMMC board is addressed at the I/O area #B40x and the AtoMMC ROM at #Axxx or #Exxx.
The BBC board shuffles the addresses and the I/O area is moved to #7xxx which does not match with the AtoMMC board.
The MMCROM is an EXTENSION ROM addressed at #Axxx or #Exxx in a normal Atom but at #Dxxx in BBCmode.
So to get the AtoMMC board operational, the ROM should be reassembled to #Dxxx and making use of I/O addresses #740x.

Last edited by oss003 on Tue Jul 10, 2018 8:07 pm, edited 1 time in total.

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Re: Acorn Atom and AtoMMC

Post by tricky » Tue Jul 10, 2018 9:09 pm

Is the 6522 (white socket in the top left I think) required for the AtoMMC board?

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Re: Acorn Atom and AtoMMC

Post by roland » Tue Jul 10, 2018 9:48 pm

As far as I know the via is not required for an AtoMMC. But I wonder if that bbc card works well without a 6522 :-k

Anyway RTB if you want to use that card, there is an improved version of the original MOS ROM at (You might have to skip the first 16 bytes of that file because it's an Atom-in-PC file). I'm quite sure that it needs a 6522 for the TIME statement to work.
256K + 6502 Inside
MAN WOMAN :shock:

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