I’ve been working to update the S-100 VDP with the AY-3-8910 sound generator and convert to VGA output.
However, I’ve hit a major roadblock and need some help to move forward on this project.
It turns out the V9938 does not generate a separate VSYNC signal. It generates HSYNC and a CSYNC signals separately however both CGA and VGA require separate VSYNC and HSYNC signals.
I imagine there is some relationship between CSYNC and HSYNC where you could synthesize VSYNC but after much studying the V9938 datasheet and numerous Google searches I don’t know how to do it.
Please take a look at the V9938 datasheet and let me know if generating VSYNC is possible and how to do it. Without a separate VSYNC we lose any hope of even partial VGA compatibility!
Thanks and have a nice day!
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