[SOLVED] Finding pinout of ASIC

[tyguy2]

I've got a chip that I need help identifying. The label on the chip reads SEGA 315-5682. It looks like the chip attached, but has a different label. Can anyone find a pinout?

[Skimask]

Ya, that's legible...

[tyguy2]

Hmm, I'll try and get a better pic of it tonight.

[Kilrah]

Maybe say what device it comes from?

[tyguy2]

Whoops, sorry. This is coming from a Game Gear hand held (see this thread https://www.eevblog.com/forum/projects/converting-rgb-scart-to-vga/). It's the main processor unit. Specifically, I'm trying to find Pins D0 - D3, the clock, csync, and hlatch.

[Kilrah]

Seems to be easy to find schematics of the GG but not of that version (VA4). Maybe the VA1 / first single chip version is "close enough" if you get lucky...

[tyguy2]

The problem is that they basically changed the resistor layout in this version I'm borrowing a V1 from a friend to try and cross reference, but it doesn't seem to be the same.

[McBryce]

The info on this site might help you: http://members.optusnet.com.au/eviltim/ggrgb/ggrgb.html

McBryce.

[tyguy2]

Whoops, sorry. This is coming from a Game Gear hand held (see this thread https://www.eevblog.com/forum/projects/converting-rgb-scart-to-vga/). It's the main processor unit. Specifically, I'm trying to find Pins D0 - D3, the clock, csync, and hlatch.

Yeah, I mentioned that in this thread.

[pmichel]

Found a clearer picture and a couple of other sites with some more information. Like Kilrah said, it's mostly for the other versions. If the LCD pads, connectors, or test points are the same you may be able to work backwards from them.
http://www.smspower.org/forums/2539-GameGearTV
https://console5.com/wiki/Game_Gear

[Kilrah]

Time to whip the scope out and look for signals that look appropriate I guess.

[tyguy2]

The problem is that I don't have anything to compare the signal to, and my scope is only 10 mhz, so I couldn't see the 32 mhz clock if I tried.

[tyguy2]

Here is a picture of my exact chip

[McBryce]

The clock signal can be found without a scope, just by following the traces from the crystal. The CSync should be easily viewable on even a 10Mhz scope.

McBryce.

[tyguy2]

Ok, I followed the traces, I think I found the clock pin. The screen freezes whenever I connect my probe to it, then un-freezes when I disconnect. Should I attach my clock pin directly to the crystal, or elsewhere?

[McBryce]

I don't know the circuit, but if the clock is buffered with something like a 74HCU04 or whatever, then I'd take the clock directly at the output of the gate.

What probe is stopping the clock? A properly setup 10:1 passive scope probe shouldn't knock the clock out.

McBryce.

[tyguy2]

I finally got the other board from my friend, I'll post my find later tonight on if the signals are a match.

[tyguy2]

Alright, I figured out the Clock signal (and finished the project). It's labeled as C27.