The discussion of using a '51 variant as a video "co-processor" for the subject platform of this thread,
caused me to do quite a bit of thinking.

Most web availiable video solutions seem "underwhelming". A bit of calculations seemed to indicate that these projects where limited by their platforms (pic/6502..) and the way they were approached.

Going down to my local "Best Buy" electronics store i purchased a $29 US 5" monochrome TV that had a direct video input.

Being lazy, and not wanting to commit to any building to support the investigation i used a 11.0592MHz DS'420 pcb i have availiable. The only external hardware was a MAX232 and a '7407 "wired-OR" video combiner.

The clock doubler, the instruction cycle rate, and the auto-incrementing DPTR(s) added important capability which resulted in the implimentation of a bit-mapped 256x175 mono TV display.

The TV's capability set the final resolution and the DS'420 retains enough free-board that a serial input/output at 19.2kBPS could be supported.

A crummy picture of the screen result can be found here. The digital camera caught the frame sync and shrinking and "jpeg-ing" causes the image to look much less "crisp" than it is.

The results justify the implementation of a small board to allow a small mini-graphic capable terminal to result.

While transacting at twice the rate of RS-170 video, in some ways a VGA is simpler than a composite video project.

External hardware required would include some VRAM, Pixel Clock, Par-Ser chip, a some glue to allow the '51 to perform sync and gate the display pixel clock.

regards,
p