Demonstration of smooth scrolling with a TMS9918A VDP

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  • Опубликовано: 15 янв 2025
  • Testing some prototype smooth scrolling code written for the rc9918 video card (based on the TMS9918A) for the RC2014 retrocomputer.

Комментарии • 5

  • @candidoj
    @candidoj 6 лет назад +2

    Amazing

  • @gasparinizuzzurro6306
    @gasparinizuzzurro6306 2 года назад

    TMS vdp did not have hw support for scrolling. Did you do tile redefinition?

    • @MichaelKamprath
      @MichaelKamprath  2 года назад

      Yeah, basically. Then then every 8 steps I blasted out a new tile pattern. You can see what I did here: github.com/michaelkamprath/rc9918lib/blob/master/examples/scroller.c

    • @gasparinizuzzurro6306
      @gasparinizuzzurro6306 2 года назад

      @@MichaelKamprath hi, from the source code i see the CPU is a z80 alike uP. Which is the clock frequency?
      there are also a lot of delays in I/O when you talk with VDP...

    • @MichaelKamprath
      @MichaelKamprath  2 года назад +1

      @@gasparinizuzzurro6306 it’s been a while since I did this, but I think the CPU was running at 2 MHz. The key to working with the TMS9918A is the blast the data update to it during its vertical refresh time. Fortunately the TMS9918A issues and interrupt to signal when that is. So, you manipulate a offscreen buffer then blast it during the vertical refresh.