200E ROMs

A place to discuss everything Dragon related that doesn't fall into the other categories.
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robcfg
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Joined: Sat Apr 04, 2009 10:16 pm
Location: Stockholm, Sweden

Re: 200E ROMs

Post by robcfg » Wed Feb 13, 2019 6:24 am

If I remember right, the original daughterboard has a jumper that switches between the standard and inverse video character sets.

What you can do programmatically is change between the 6847’s INTernal character set (the standard Dragon one) or the EXTernal one (the one in the daughterboard).

bluearcus
Posts: 44
Joined: Wed Sep 07, 2016 4:45 pm

Re: 200E ROMs

Post by bluearcus » Thu Feb 14, 2019 11:46 pm

A bit of disassembly of the ROMs and then some searching on here...

CLS 9 switches the G0 value in text mode and determines whether character set 0 or 1 from the ROM is used. It stores details of the mode setting in bit 4 in zero page $77.
This isn't switching INT/EXT character set.

Sixxie and co already nailed it in Xroar since 2013 it seems! The latest MAME version I have, not so much...

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