I was thinking about building a separate video processing unit for the games console. This way I can just have the CPU write to the video memory and the screen will update. We would have a separate GPU which can render the VGA signal from the memory. The BB (Bus Busy) and BE (Bus Enable) lines work in tandem to provide bus control. The GPU is the bus master and the CPU is slave to it. I've done it this way to reduce I/O lines and because I expect the GPU to use the bus more, plus the GPU has timing constraints to work with. With the unit designed like this we hopefully stop partial read/writes and any other mess-ups that might happen because we need to have a shared bus.
This is what I've come up with, an 8bit design for a 8bit bus. Enjoy!
Napalm
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