Jeff,

As Jan mentioned, RAMDACs are high speed DACs characterized for analog video work. Often they pair with Look Up Tables (LUT) which allow restricted pixel widths to generate specific larger width color values. For example the ability to generate 256 - 32 bit color values.

While the platform video is characterized for single bit monochrome, adding only a single bit to the existing Video DAC would provide hi/lo intensity monochrome and the provision of 4 pixel bits would provide 15 grey scale values. This increased ability would only require 24k of Frame Buffer which is still quite small and easily manipulated using the DS'420 Data Pointer extensions.

For demonstration purposes i have used the internal 1k SRAM. For useful video i have found that PAGE Mode 1 memory implementation occuring 4 times faster than the quickest Non-Page Mode memory access is most appropriate. You do however need Fast SRAM.

Perhaps you are familiar with this mode, any access to data within the current "page" is single cycle. When you have to change the high address value then you incur an additional cycle. If a video line corresponds to divisors of 256 then you can easily build the page latency into the video timing.

regards,
p