[Coco] CoCo RGB video timing and levels

[James Dessart]

I'm trying to do some calculations to figure out how to interface with the
CoCo's RGB port. Now, on an NTSC CoCo, we have a vertical retrace of 59.95
Hz, and a horizontal sync of 15kHz. Based on this, and the standard size
of an NTSC frame, it seems that the pixel clock would be 10MHz, am I right
in that calculation? or around 11 MHz for a 720 width NTSC frame.

Also, what are the levels for the RGB lines? I know there are only 4,
since the CoCo can only output two bits per component.

James