It works by using a smart LCD controller to generate the graphics and then another chip that encodes the RGB data into a HDMI signal.
The microcontroller connected tot he shield can send high level commands to the RA876 chip such as draw line, copy raster and render text, so the performance is not limited by the slow controller.
The RA8876 allows communicating with it through different means. The Arduino boards use SPI, but it also provides 8 and 16-bit parallel interfaces (6800 and 8080 bus protocols.) -- The makers of the shield even added a header for accessing these alternative communication interfaces.
So in theory, one could use the shield directly in combination with an Atari ST. In order to do that, one would have to create an additional board that:
- Does address decoding for accessing the registers on the RA8876.
- Contains level converting buffers for the data bus, as the RA8876 signals are 3.3V only.
- Optional: I2C chip to talk to the HDMI converter, as otherwise the resolution is hardcoded at the default setting stored on the board's serial ROM.
- Write a driver for fVDI to use the card.
The chip even has an internal blitter for copying data around on the board's SDRAM chip (and even from flash ROM.)
It has a mode where the operation is started, and the controller supplies the source data through the interface -- All shifting and palette lookups will be handled by the RA8876.
Is this something people would be interested in?
