[comp.misc] Request: Video output circuit design help needed

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!/