Getting a ntsc clock signal from the nes

[Drakon]

Since my super upgraded rgb consoles use video encoders I wanted to find a way to use the nes master clock signal to get the required speed to drive the video encoder circuit I add to the system.  The kit I order has a separate crystal oscillator to drive the video encoder but when you drive a video encoder from the same clock source as everything else on the system you'll get a better quality picture.  I poked around the internet finding out what the clock speed of the nes is and what clock speed I'd need.  The speed I need to drive my video encoder is 1/6 the speed of the nes clock signal.  I poked around the internet trying to find a shematic on how to build a circuit that divides a clock signal to 1/6 but all I could find was theory schematics as this's sort of a circuit that in most situations isn't necessary.  I bugged tiido for some help this morning (he's the guy who created the amazing sega genesis crystal clear audio mod circuit).  Tiido concurred that my theory of using the nes master clock to drive the video encoder would indeed improve the video quality.  Tiido found the same theory diagram that I found and said that's what I needed to build.  Tiido also told me what parts I needed to buy and helped explain some of the wiring to me.  I bought the parts today and wired them up (two ics).  The wiring is....complicated.....but wouldn't you know...it worked first try....and indeed the picture quality noticably is sharper than before.  I'll draw up the schematic when I get the time and post it.

[Drakon]

So you talking about typical divider by 6? Complicated? Oh, yeah 74ALS161B Philips semiconductor datasheet, page 3 figure 1 Maximum count modifying scheme terminal count=6

Go ahead and build it and see if it works.

[famifan]

the typical divider won't work because the video encoder need a sine wave signal, not square. Am i right?

[Drakon]

Anyway here's what I built and it works flawlessly.  These are two very common IC chips I was able to pickup at a local store.  The 21.47 mhz input I grab from the ppu clock pin (ppu pin 18)

[Drakon]

So... where is the sine wave signal?

one connection says 21.4 mhz input the other says 3.58 mhz output....is that what you're asking about?

Both me a tiido did random google searches on clock frequency divider circuits and everything we found pointed to using flipflop chips which is what these two chips are.  The first chip divides the signal by 1/3 and the second by 1/2 to equal 1/6 when combined.  I don't know if the nes uses a sine wave I just know that these chips work when you want to divide the frequency of a clock signal.

[Drakon]

So... any divider by 6 will do the job, isn't it?

If it's a flipflop I would imagine so.  I have no idea about using anything else, I didn't try anything else.  Me and tiido just brainstormed over how to make something that could work based on what we found from google searches and this is what I constructed based on that and it happened to work right away so I never tried anything else.  All my google searches for building a circuit to divide a clock signal frequency showed circuits using flipflops.  Tiido explained to me how to read the schematics, what parts to buy and the basics of the wiring.