Re: Vectorlist: Re: Wico XY Pattern Generator Schematics?

The Electrohome pattern generator has a very simple RGB output arraignment.
They ALL run off the same video signal, so they overlay each other
completely. Thus the generator under discussion could be for B&W as easily
as for colour, just need to set the frequency and patterns, and each colour
is added by a switch to the signal line. After all we are just testing the
monitor, we aren't that interested in mixing colours, are we?

John :-#)#

At 05:16 PM 3/30/2000 , Clay Cowgill wrote:

>>clay has my wico generator, don't know if he ever traced the circuit
>>out or not. from memory, it was a lot more complicated than I thought
>>it would be. A microcrontroller and a couple of DACs would do everything
>>that box did.
>
>Yeah, I took a look at the Wico color one with the intent to trace it out,
>but it's too damn complicated.
>
>I was thinking an OK design might just be something like:
>
>Two big EPROMs in parallel (16 bits wide), or one bit 16 bit wide EPROM.
>One 10 to 12 bit DAC. A couple of sample and holds feeding the X/Y output
>circuitry. Two 4040 counters and a clock oscillator.
>
>The EPROM bits are used as:
>
>DAC Data (12 bits)
>RGB (on or off for each color) (3 bits)
>Done (1 bit)
>
>The EPROMs just hold X,Y,color data at each location. Odd addresses are
>the Y axis, even addresses are the X axis. Each sample and hold is
>updated based on the A0 line and goes to the X/Y outputs.
>
>A PC vector-drawing program (like my old Sega vector editor) would just
>output a list of XY coordinates and colors. Essentially just a sequential
>list of pixels. The 4040's are cascaded to make a big free-running
>up-counter. The up counter connects to the address lines of the EPROMs.
>The top address lines on the EPROMs go to a rotary switch or something to
>select one of several "pictures". The 4040's free run, sequentially
>addressing all the data in the EPROM until they hit the "done" bit which
>causes them to reset and start counting again.
>
>The frame rate would be variable depending on the drawing complexity, but
>the PC could add a lot of "black" drawing at the end of the display list.
>If you used the top three lines of the EPROM address bus to select the
>image you'd get 8 64K word "programs". That would be 32K "pixels" per
>program, or about 32 "full screen" lines at 1024x1024 resolution. (So a
>convergence grid would probably be the most complex image, maybe 16x16
>full-screen lines.)
>
>Anyway, it'd be relatively simple to make... (Although a little
>microcontroller could just as easily run the DACs too, I just liked being
>able to use the PC to draw stuff easily.)
>
>-Clay
>
>
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Received on Thu Mar 30 22:32:56 2000