NTSC/PAL encoding

[Penio Penev <penev@xxxxxxx>]

I'm trying to underestand whether I can use the video out of P21 for a 
general analog-out signal.  For example, can I program it go give 1 bit
(ON/OFF) signal?  2-bit?  n-bit?

Does anybody know of a good description of the NTSC signal?  Availbale
through the web? 

The whole point is to use the external clock as a reference of a signal
that comes out.  Otherwise i would have to connect an external timer, and
read it in polling mode, which would result in temporal jitter in the
analog signal that I output. 

If I could use the video out as a 1-bit high frequency ADC, I could do
audio out with the correct oversampling and filtering. 

--
Penio Penev <Penev@pisa.Rockefeller.edu> 1-212-327-7423