Re: Apple II Video Generator

[Immortal Nephi <Immortal_Nephi@hotmail.com>]

On Saturday, October 20, 2012 2:18:40 PM UTC-5, Kevin wrote:
> On Saturday, October 20, 2012 1:50:03 PM UTC-5, Immortal Nephi wrote: > I researched to get more information about NTSC video composite signal. I looked at the IRE waveform picture with color & monochrome bar test. The waveform has sync signal, color burst signal, and mixed luma & chrominance signals. > > The luma signal looks like square wave and the chrominance signal looks like sine wave. > > My understanding is that Apple II video circuitry generates square wave into picture signal. If each bit in the square wave is turned on, then it is in white reference otherwise if each bit in the square wave is turned off, then it is in black reference. It does not say if it is in the middle between black reference and white reference. It is considered to be true black & white as monochrome, but not grayscale. > > Do anyone have oscilloscope equipment to connect to the Apple II’s video port? Can they be able to lock on the color burst signal before picture signal in IRE will be shown on the oscilloscope screen? Zoom waveform to 70 nanoseconds. > > What do picture waveform in IRE look like? > > > > Bryan not entirley sure what your asking, color burst is just a 3.579 Mhz sinewave, and based on how "shifted" the video signal is effects what color is shown, video itself is an analog waveform going from black to white, and anything between is greyscale, apple2 doesnt have greyscale so its on or off (hince the square wave)


I am trying to explain.  My question is -- are you able to connect Apple II's video port to an oscilloscope?  If yes, you should be able to lock on either H sync or color burst before you will be able to see horizontal line at 63 microseconds and zoom square wave to 70 nanoseconds.

I draw a picture to demonstrate IRE.  IRE shows picture signal.

IRE A
White reference  ->|  ___    ___    ___
                   | |   |  |   |  |   |
                   | |   |  |   |  |   |
Black reference  ->|_|   |__|   |__|   |_
                   |
                   |_____________________
                            time

IRE B
White reference  ->|___
                   |   |___
                   |       |___
Black reference  ->|           |___
                   |
                   |_____________________
                            time


Which IRE A or IRE B do Apple II video circuitry generate picture signal as square wave?

It looks like that IRE B is chosen because luma is used while no chrominance information is present in the picture signal.

That is all I need to know.  Please confirm.

Bryan