You were right RB, what I saw was not overlapping writes with dual device cs happening in MAME, the latter overloaded the first as you said. What I saw instead was a 16 bit write setting two registers. So effectively the esselte 100 sets four registers divided over two devices in a single 'stx $c818'! The Didact design team must have had fun doing this!

So I add a handler for writes too now and things should move forward..

Some progress with the Esselte 100, I got BASIC up and running.

Still a lot of stuff to fix but now it will be easier to find the corner cases.

Is the cassette interface capable of record BASIC programs or would that be the memory "snapshot" feature? How does it work?

for cassette, you need to find which bits are the cassette writes first... then the tape interface in the UI and its internal handling will direct it to a wav file

any home computer with a cassette drive is a good example for plain cassette hookups (things get a bit more complex only when you want to support "compressed" cassette formats created for emulators like CBM .tap, MSX .cas, etc.)

Great, that is the next thing I'll do, using save/load from the debugger now. Here is a clip of a animation(!) demo on a 2MHz 6802 with 16Kb ROM and 1Kb of RAM: Olympic Rings EDIT: Recorded in MAME with -aviwrite of course

Ok, so Esselte 100 PR posted including cassette save/load, thanks for all the help!

I have also uploaded a single driver beta binary for Windows 7 if someone want to play with it, it is available through my very sporadic blog http://frakaday.blogspot.se/

Another Didact design bites the dust, the Modulab. I came across a unit in an auction a year back or so and contacted one of the designers from back in the days that I'd had have some email conversations with on an Electronics forum. He found all sorts of documents including firmware sources and a technical manual so here it is and indeed the system I started this thread about:

Updating an old layout for the Didact md6802 design now that I start to get a hang of it, the repeat and grouping tags are really powerful and intuitive.