Re: Apple II Video Generator

[Michael J. Mahon <mjmahon@aol.com>]

Patrick Schaefer <pa.schaefer@web.de> wrote:
> Am 21.10.2012 05:58 schrieb Immortal Nephi:
> 
>> The NTSC monitor is supposed to use luma by recognizing the
>> ercentage between 0% and 100%.
> 
> An Apple II is only able to generate 0% (low) and 100% (high). There are
> no values between that.
> 
> The position of a pixel in relation to the color burst determines its
> color. Every even pixel is pink, every odd one is green. When both
> together are on, it looks like white. When both are off, it looks like black.

Just one quibble--it doesn't just look like white or black, it really is
white or black.  Since two consecutive hi-res (7.16MHz) pixels in the same
state contain no 3.5MHz component, a color monitor will see a chroma
component of zero amplitude, so no color. 

> Since Rev 01 it is possible to delay the pixel clock by a quarter period
> of the burst frequency. This gives another two colors: orange and blue.
> Again, when both are on you get white, when both are off you get black.
> 
> 
> Patrick

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon