System 6809 ROM

discussion of games, software, hardware & emulators relating to the Acorn Atom and Acorn System machines.
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Prime
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System 6809 ROM

Post by Prime » Thu Sep 20, 2018 10:43 am

Hi all,

I've just created a git repository of the source to the Acorn 6809 card ROM : https://github.com/prime6809/System6809

This was created from disassembilies of the MAME copy of the 6809 card's ROM and a copy dumped from the machine at the CfCH at the recent ABUG meetup. Comments are largely taken from the listing in the user manual.

The main difference between the two is that the CfCH ROM has been modified so that the periperals appear in the $E000 - $F7FF range so that the machine can have RAM in $0000-$E000 without holes in it. The CfCH rom has also been patched for 80 column video and to auto-boot from disk.

Now to go design a modern version of the card :)

Cheers.

Phill.

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Pernod
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Location: Croydon, UK
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Re: System 6809 ROM

Post by Pernod » Fri Sep 21, 2018 10:06 am

Thanks for the analysis. I already knew it used the VDU80 card but didn't know the significance of the BLK0 line and that the FDC card uses this to move it's IO to &EA00.
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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