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Video from dual-port RAM | by jdripper
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Video from dual-port RAM

The CDP1861 PIXIE uses DMA to read memory and directly shifts the bits out as video. In my design, because the CPU may be run at various speeds, from 1x to 256x the original Elf speed, the PIXIE logic will write bytes into a dual port RAM, and dedicated logic will scan them out as NTSC monochrome video. In this test, the CPU is not hooked up, and the frame buffer data is statically initialized to match the screen shot at the beginning of the July 1977 Popular Electronics article, page 41.

 

Due to an error in my design, the rightmost pixel column is being displayed on the left.

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Taken on October 22, 2017