robbin@resrch.MoliEnergy.BC.CA (Robbin W. Johnson) (01/14/89)
I am looking for information and/or help on how to design a video display driver. I have a 1 bit deep display memory and I want to end-up with a circuit that will shift this out to a monitor. The design will generate the pixel stream and the horizontal and vertical sync pulses along with any signal level shifting necessary (I believe this to be all I will need, please correct me if I am wrong.) What I would like to end up with is something closely resembling the original Blit, but I doubt that Messrs. Pike or Locanthi would be able to (or even want to) send me some of their hardware design secrets :-) [I am doing this mostly as an exercise to see if I still have it in me to design and build such a beast and because I find the Blit to be a rather fascinating concept. Please no "just use a 6845" or "why not a 7220?" replies. I have looked at these and other, newer chips and they do not interest me.] The design will be implemented using PALs, shift registers and binary counters. I already have a design for the RAM dual-port circuit. What I need is help designing everything that deals with the raster image after the CPU has put it into memory. I am hoping to end up with a display on the order of 1024 X 768. In addition I need to find out a few facts about monitors. Is a 60 Hz. display capable of displaying more lines if you run it at only 30 Hz.? Can you up the pixel clock and feed more pixels per scan line? Does all this require surgery on the display's sweep circuitry or is there such a thing as a magic, self compensating circuit? It seems to me that a 25Mhz display is capable of displaying more that 720 X 3XX(?) pixels, especially if you go from 60 (or 50) to 30 Hz refresh. I suppose that there are limits based upon the phosphor's particle size and/or the electron beam size. I guess what I really need is a "Video Designer's Cookbook." Anyone know of such an animal? Any and all help would be greatly appreciated. Robbin W. Johnson -- Robbin Johnson ...!ubc-cs!van-bc!resrch!robbin robbin@MoliEnergy.BC.CA ...!uunet!/