Small Update:

I got the TN-VDP working in 40 and 80 columns and just today I figured out how to get the Vsync interrupts working on my eZ80 board.
The rev2 board will include some changes. Of course I have reversed the data bits, and I also added a diode to the INT pin to make it compatible with an open-collector type bus.

I am very pleased with the speed so far. at 36 MHz, I can drive it with an IO cycle time of only 200ns, equating to 4.8 MHz

After a week of unsuccessful debugging, someone else gave me the deciding clue:
I had the data bits reversed!

With the bits reversed in software, it works just fine. There are more tests to be done, but it seems like the card will be working perfectly.

Repórter Retro 095

https://retropolis.com.br/2023/08/30/reporter-retro-095/