[Coco] PICs and S-Video

[Chris Hawks]

---Reply to mail from Mark Marlette about [Coco] PICs and S-Video
> 
> If all of those parts are just to provide an inversion for the delay. 
> I would go with the inverter. You can get 4 pin devices, SMT, won't 
> even know they are there. Last time I looked they were around $0.14 
> each. R/C are around $0.01. Total them cost is about the same...Where 
> you will save time is in assembly.

    An invertor would only replace 2 resistors and 1 capacitor. We have
two timing circuits (1 resistor and cap each) and 2 pulse 'massagers' (2
resistors and 1 cap each).

The output from the Coco3 is:
_____--________________--________________--______
and the input to the first timer needs:
-----_-----------------_-----------------_-------

The output from the first timer is:
_____-------------_____-------------_____--------
and the input to the second timer needs:
------------------_-----------------_------------
and outputs:
__________________--________________--___________ 

    This delays HSYNC almost one whole line and fools the display into
thinking HSYNC occurs earlier.

BUT!!! I found a Dual Retriggerable Monostable Multivibrator chip (the 555
mode we're using) that edge triggers!!! (High to Low or Low to High) This
means the circuit only requires 2 resistors and 2 capacitors (for timing).

    I bult the circuit (on my Experimenter Board, And it Works(!!)
perfectly.

John:

    I'll send a schematic as soon as I draw one.


---End reply

Christopher R. Hawks
HAWKSoft
-------------------------------------------------------------------------
On the Internet, no one knows you're using Windows NT
    -- Submitted by Ramiro Estrugo, restrugo at fateware.com