Sync Types

[Icelvlan]

Hello,

Is there a reason I should use ttl vs csync with nes/snes/n64?

I have the option to do both and I know there is no difference between sync. I think that having a compatible ttl sync cable is better than accidentally using a csync cable on a ttl system.

[Fudoh]

TTL describes the voltage levels on the sync signal.

csync usually just describes a clean sync signal (over composite video or luma for sync).

CSync at TTL levels is only required for very selected gear. Unless you know that you need it, it's safer to go for consumer voltage levels ("75 ohm sync") instead.

Not sure what you have in mind when saying "accidentally using a csync cable on a TTL system".

[Kez]

I think OP means accidentally using a passthrough cable on a system that outputs TTL (ie sending TTL to your device).

As far as I understand it, the only real advantage of choosing the TTL option when modding is compatibility with system "standard" csync cables. So if you buy a premade csync cable for SNES or Genesis, they will have resistors on the sync line.

Having passthrough cables and 75 ohm csync output from your device is marginally better from an electronic standpoint but rarely makes a meaningful difference in reasonable length cable runs.

If you're worried about cable mismatch, you'd ideally want all your cables to be the same that use the same connector.. And all your mods to expect the same cable. Say you have a stock snes with csync cable, and then a modded n64 with no resistor in the cable.. Swapping those cables would make your SNES output high voltage.

[Icelvlan]

Correct, I wouldn't want to use a comp sync cable on a ttl console.

I know most of my consoles do ttl sync (genesis etc.)

The cables are easy to mod for comp sync, but does ttl have a disadvantage besides higher voltage? I'm going into hardware that can handle it since there is 470ohm resistor inline.

[Josh128]

If what you are feeding into has a 470 ohm resistor in-line, you will want to feed in TTL level sync as the resistor will drop the voltage down to the sub 1 volt level. If you feed with non-TTL sub 1 volt (75 ohm) sync level, you risk dropping to too low a voltage and having sync issues.

[Icelvlan]

That’s correct, feeding ttl with resistor in-line. My question is this recommended vs csync?

[makar1]

That’s correct, feeding ttl with resistor in-line. My question is this recommended vs csync?

The recommended way to use CSYNC is to copy how existing consoles did it. The SNES and Megadrive/Genesis output high voltage TTL level CSYNC from their AV ports, requiring cables with in-line resistors to bring sync voltage back down to 75ohm levels.

Modding a console with TTL-level CSYNC output (on the expected CSYNC pin of the Nintendo/Sega AV port) allows you to use the same in-line resistor RGB cable across all your consoles (stock SNES, modded N64) without any danger of damaging your equipment.

[Icelvlan]

That answers my question

[the Goat]

That’s correct, feeding ttl with resistor in-line. My question is this recommended vs csync?

Icelvlan, you need to understand, choosing between TTL and csync makes no sense. TTL vs. csync is not a thing. I think you are actually asking about choosing between TTL and 75 Ohm voltage levels of the csync signal.

[Icelvlan]

Yeah, I understand that. Either ttl or 75ohm sync.