I had to re-engineer the firmware to get anything to display on it reliably. Source can be found on my github.

The circuit uses a logic state machine for the display, along with an IRQ line sent to the CPU which is then responsible for updating an address pointer in the video circuit so that it will show multiple lines of text. There is also a header on this board that the user manual mentions as being an expansion port for a graphics system. I doubt I will ever find any more info on this, let alone the actual card!

I did manage to get a copy of it's original firmware thanks to Dave from davesoldcomputer.com He had someone else pick up his DT80, and they were able to ship me the ROM chips for reading. I was sure to let them both know that they have a rare terminal.

If anyone else has any info, schematics, or a keyboard they know about or would like to send to me to borrow or have, please contact me!