32x s-video & RGB - Where do things stand?

[AG-Wolf]

I've poked around on the forums for a little bit trying to find what kind of info is available on the subject, but haven't come up with much...  I understand the 32x does some kind of video pass-through sorcery to superimpose its own video with whatever it makes the Genesis do (ie; in Knuckles Chaotix, the Genny is used for the background scrolling and such, and the 32x does the sprite work, scaling, rotating, 3d effects, etc)

Anyway... due to whatever douchebaggery sega made this hardware combination accomplish, it seems s-video has eluded people still.  I traced the composite output from pin 4 on the a/v connector, through the cap and resistor, and found it lead to some nondescript IC labeled "315-5788" (see attached image, it's the one on the right side of the cartridge slot), coming off of pin 20.  Now, considering this is the composite source, do you think it's safe to assume this chip is responsible for the 32x's video processing?  I didn't trace the RGB lines yet, but visually they look to follow the same kind of pattern toward that chip.  I don't have an o-scope at my disposal to get some kind of visual signal representation, so I can't see what the signals off a regular genesis' cxa1145/1165 look like to get an idea of what I'm trying to find off the 315-5788

Is there anyone else who can look into this? HAS anyone figured anything else out? lol

I found one possible solution over on Sega-16's forums:
http://www.sega-16.com/forum/archive/index.php/t-224.html

I figured out a REALLY easy way to fix all this... All right this is simple, it takes one chip, and a bunch of 75 ohm resistors.

This chip:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3861855695&category=4663
yep that is the CXA1645M... the same chip found in the genesis 3. If you take the RGB and sync and put them into this chip it will do all the work for you and output beautiful Svid, composite, component, RGB sync on hand, and all for like 22 dollars in a really SMALL case. AND you can make it so that you can use the TINY little box to convert any RGB (low frequency that is.... not computer, basically your video game consoles) signal into all those freaking signals all in one easy step! OMG... why didn't I think of this before, why am I sitting down writing schematics and trying to think of cheaper ways to build a freaking smaller box when all I need is a measily 1/2 cm by 1 1/2 cm damn chip and a couple resistors. I hope it works... im gonna test it out and I'll let you know!!!!

Now, I've already done the s-video mod to a genesis 3 with the cxa1645m, ludicrously simple, very painless, looked great.  I have no issue scouting out a standalone 1645 chip, but my only concern is whether or not I would feed it RGB from the pins on the A/V jack, or if I should trace them back to their source and pull from there...  I don't know if the signals are fed through a cap and resistor like the s-video and composite signals, or if that would interfere if the signals are indeed filtered like that.

I still am hesitant to try this, though, because if there's a chip somewhere inside the 32x that actually outputs chroma and luminance signals just like the Genesis 3's 1645, it would be so much easier.

Wow I ramble a lot... at any rate, any help is appreciated thanks in advance

[kendrick]

I did some research on this a few years ago. In a nutshell, the 32x doesn't product chroma or luma natively at all. You only get RGB or a processed composite video out of it, so if you want to get an S-video signal you have to add components.

[AG-Wolf]

Alright, well at this point, i don't mind "adding components"

I think Im gonna try to go the route of sending the 32x's RGB+Sync lines into a CXA1145/1645 encoder chip and just using the output from that. My only problem, though, is that both chips have (or rather need?) more signals than merely the RGB lines and sync in order for the chip to operate...  this site:
http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm
has PDFs of each chip's data sheet...

Pin 6 is XO/Subcarrier input.. I don't know if I need to add that
burstflag, timeclamp, Ytrap, all sorts of other jargon that I'm not exceptionally familiar with... Shouldn't I just be able to send the RGB and Sync signals from the 32x's AV Out connector into this chip and get my Y/C for Svideo?  Or do I have to really add all the other junk?  The more I look at it, the more I realize the RGB signals are just passed right through the chip, so does that mean all the other extraneous connections ARE for composite/svideo?

[Tiido Priimägi]

that chip is RGB overlay+underlay chip + RGB to s-vid/composhit encoder... the 32X hardware maual says the system has S-vid so it must be there somewhere, BUT I do not know where exactly... I made a schematic of the circuit there, I'll put it up when I find it.