This was exactly one of the many hardware projects that were published in the spanish magazine microhobby.
Long story short: it added 16K of RAM that was mapped at 0, and allowed both manual control with buttons or software control via a port to decide if it is mapped only for writes or it is mapped for both reads and writes.
Long story short: it added 16K of RAM that was mapped at 0, and allowed both manual control with buttons or software control via a port to decide if it is mapped only for writes or it is mapped for both reads and writes.
https://microhobby.speccy.cz/mhf/103/MH103_20.jpg https://microhobby.speccy.cz/mhf/103/MH103_21.jpg https://microhobby.speccy.cz/mhf/103/MH103_22.jpg
https://microhobby.speccy.cz/mhf/104/MH104_22.jpg https://microhobby.speccy.cz/mhf/104/MH104_23.jpg https://microhobby.speccy.cz/mhf/104/MH104_24.jpg