ubb-vga, with DMA

Werner Almesberger werner at almesberger.net
Sun May 1 17:13:29 EDT 2011


David Kuehling wrote:
> Without going through your sources: Can this do (circularly linked) DMA
> transfer lists for doing a full frame without CPU intervention?

The DMA only provides the pixel data. The CPU still needs to bit-bang
hsync and vsync.

Exclusively DMA-based operation would only be possible if at least
three colors would be assigned to sync generation and if there was
some logic circuit to derive the sync signals from this.

Another issue is that the number of blocks in an MMC transfer is
limited by the controller, so the CPU would have to intervene and
set up a new transfer about once a second.

> (Still hoping for video playback :)

There's still hope that interrupts may be fast enough :-)

- Werner




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