about the video. Requires intermediate video memory. The size should match the resolution and color depth. For 1024 * 768 and 16 bit color (5-5-6) 1024 * 768 * 2 bytes. Static memory, you can connect yourself. For the dynamic - it is better to take a ready-made controller.
For this controller, if it requires one port will produce an arbitrator.
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The arbitrator will distribute access continuous reading from the memory of VGA DAC and record the new values of the processor.
Controller sd_mmc - access device to the card. In the simplest case, this SPI controller.
The processor must read the file from the card and turn it into a sequence of bytes to write to video memory.