Does NES have an A/V Pass-through?

MM007 · Post by **MM007** » Sat Oct 23, 2004 5:55 pm

I want to know if there are audio and video pass-through connectors it the cartridge slots in the NES. Also, if any exist on the SNES, N64, Genesis, that'd be a good thing to know. ^^

I want to make an Atari-in-a-cart, but since I am asking about NES passthrough, I put it here.

Post by **gannon** » Sat Oct 23, 2004 6:45 pm

hmmm...not sure, but since the SGB has all of the GB hardware in it there might be in the snes. Then again, it might just output code and then the snes decodes it.

JackFrost22 · Post by **JackFrost22** » Sun Oct 24, 2004 5:43 am

I don't think it would because you had to plug in the super 8 gannon.

Post by **gannon** » Sun Oct 24, 2004 10:36 am

ahh....good point. I suppose you could actually use the unused pins on the nes 72 pin connector to transmit a/v if you wanted to build a custom cart though.

HK-47 · Post by **HK-47** » Sun Oct 24, 2004 10:40 am

Ooohhh..... Its what the "mysterious extra pins" on the game carts are for....

MM007 · Post by **MM007** » Sun Oct 24, 2004 11:55 am

HK-47 wrote:Ooohhh..... Its what the "mysterious extra pins" on the game carts are for....

I thought the extra pins were used for the NES "lock-out" chip which the Famicom lacked.

Also, how would I make this pass-through cart? I do have an electronics background, an EEPROM burner, and some spare 27CXXX chips lying around specifically meant for NES cart mods(^^).

Post by **gannon** » Sun Oct 24, 2004 12:19 pm

well, the pins are used for something, but if you disable the lockout chip in the nes or are using a noac, the pins are no longer used, so you can transmit a/v over them. You could even use a relay or something that automatically switches the a/v output from the nes to the cart.

SgtBowhack · Post by **SgtBowhack** » Wed Dec 08, 2004 5:51 am

Actually, you don't need to use the lockout pins at all. There are 9 pins that have (as far as I know) NEVER been used by any NES cart. Those pins on a normal NES would go to the expansion port on the bottom of the system, but if you're feeling adventurous enough, you could redirect them to video output circuitry... in fact, that idea is quite good, I think. I may have to do this myself... though the problem would lie in getting controller input/output from the NES... you'd probably need some sort of ROM in the cart that uses the NES code to do that. How it would work, I do not know. Honestly, there is enough similarity between the 2600 and the NES that some of this may work out... the 6507 in the Atari and the 6502 in the NES are close enough that the programs should actually run. It's all a matter of I/O and stuff.
Then again, the same is true of NES games running on the SNES...
Anyway, good luck with it. It sounds like quite the interesting project.

FYI, it looks like the Genesis does have video in on the cart slot, but not audio... but it has audio in on the expansion port if that helps.

MM007 · Post by **MM007** » Wed Dec 08, 2004 7:18 am

Excellent..I'll have to look into that. ^^ Which 9 pins are those, and which pins are video (and hopefully audio) on the expansion port of the NES?

As for the genesis, since the Atari is mono, maybe the speaker could be in the cartridge if I wanted to go mono...

SgtBowhack wrote:Actually, you don't need to use the lockout pins at all. There are 9 pins that have (as far as I know) NEVER been used by any NES cart. Those pins on a normal NES would go to the expansion port on the bottom of the system, but if you're feeling adventurous enough, you could redirect them to video output circuitry... in fact, that idea is quite good, I think. I may have to do this myself... though the problem would lie in getting controller input/output from the NES... you'd probably need some sort of ROM in the cart that uses the NES code to do that. How it would work, I do not know. Honestly, there is enough similarity between the 2600 and the NES that some of this may work out... the 6507 in the Atari and the 6502 in the NES are close enough that the programs should actually run. It's all a matter of I/O and stuff.
Then again, the same is true of NES games running on the SNES...
Anyway, good luck with it. It sounds like quite the interesting project.

FYI, it looks like the Genesis does have video in on the cart slot, but not audio... but it has audio in on the expansion port if that helps.

HK-47 · Post by **HK-47** » Wed Dec 08, 2004 2:21 pm

SgtBowhack wrote:Actually, you don't need to use the lockout pins at all. There are 9 pins that have (as far as I know) NEVER been used by any NES cart. Those pins on a normal NES would go to the expansion port on the bottom of the system, but if you're feeling adventurous enough, you could redirect them to video output circuitry... in fact, that idea is quite good, I think. I may have to do this myself... though the problem would lie in getting controller input/output from the NES... you'd probably need some sort of ROM in the cart that uses the NES code to do that. How it would work, I do not know. Honestly, there is enough similarity between the 2600 and the NES that some of this may work out... the 6507 in the Atari and the 6502 in the NES are close enough that the programs should actually run. It's all a matter of I/O and stuff.
Then again, the same is true of NES games running on the SNES...
Anyway, good luck with it. It sounds like quite the interesting project.

FYI, it looks like the Genesis does have video in on the cart slot, but not audio... but it has audio in on the expansion port if that helps.

This is what gannon said a few posts up...

gannon wrote:ahh....good point. I suppose you could actually use the unused pins on the nes 72 pin connector to transmit a/v if you wanted to build a custom cart though.

To answer the question: the pins that people are talking about are the missing pins pictured here.

What is being said is: since these pins run to the expansion port on the bottom you could just tap those for pass through. You would just have to hack a thing that connected to the port on the bottom, and connect av pins to the appropiate plugs.Id draw a pic but my linux mouse setting suck and its hard to draw anything...

SgtBowhack · Post by **SgtBowhack** » Wed Dec 08, 2004 4:04 pm

Yes, I know he mentioned that but I am trying to say that the lockout pins should be left alone, IMO. There are already 9 pins (well, 10, really, but one is apparently sometimes maybe kinda used for something... there's at least a Famicom equivalent) that serve no purpose, so using the lockout pins are not worthwhile.
You know... the NES expansion port has video and audio out, which might be useful for your project... you could instead make a Gameboy Player-style device for the NES to play 2600 games, at least, and use the cart slot for a ROM that reads the controller input and sends it there. Just an idea

Good luck with it, in any case!

JackFrost22 · Post by **JackFrost22** » Wed Dec 08, 2004 4:37 pm

Yeah you should build some stuff in thoguh

MM007 · Post by **MM007** » Wed Dec 08, 2004 9:13 pm

SgtBowhack wrote:Yes, I know he mentioned that but I am trying to say that the lockout pins should be left alone, IMO. There are already 9 pins (well, 10, really, but one is apparently sometimes maybe kinda used for something... there's at least a Famicom equivalent) that serve no purpose, so using the lockout pins are not worthwhile.
You know... the NES expansion port has video and audio out, which might be useful for your project... you could instead make a Gameboy Player-style device for the NES to play 2600 games, at least, and use the cart slot for a ROM that reads the controller input and sends it there. Just an idea
Good luck with it, in any case!

...hmm....I wonder if I would even need a cart then...maybe just to keep the lockout chip busy and make the NES controllers work with the Atari...

JackFrost22 · Post by **JackFrost22** » Wed Dec 08, 2004 9:15 pm

i dont think you do only a pass through

SgtBowhack · Post by **SgtBowhack** » Thu Dec 09, 2004 12:55 am

You could be right- it looks like the controller signals are sent to that expansion port too... you could go about it two ways then.
1) Get the NES's controller data and decode it using a serial->parallel IC in your Atari Player (TM!) - But in this case, you'd probably still need something in the NES side of things to kill the video signal that the NES has when it's turned on without a cart (a gray screen). You may just want to add a switch on the front of it that allows NES video/audio passthrough or doesn't *shrug*
2) Have the NES do the dirty work for you, and make a small program that sets the expansion port pins high when you press certain buttons on the pads. Personally, I think option 1 is probably best... in that it's also easiest I think. You'll need the NES' clock signal though as the clock signal for the serial->parallel IC though.