FDS Cart rear Port

[aricsdaddy]

Hello everyone,

Can anyone tell me what the rear port was designed for on the FDS Cartridge? (The one on the back with sliding cover)

Thanks.

[P]

It's an expansion port but I believe it officially remained unused.
It contains 6 I/O pins and I think you could also output expansion sound through it, but I can't find any info about that on the Nesdev wiki so I might be misremembering.

[aricsdaddy]

It's an expansion port but I believe it officially remained unused.
It contains 6 I/O pins and I think you could also output expansion sound through it, but I can't find any info about that on the Nesdev wiki so I might be misremembering.

Thanks :-)

[Jedi Master Baiter]

Apparently audio comes out of one of the pins, according to ImATrackMan:

More info here: https://www.famicomworld.com/forum/index.php?topic=12002.msg162415#msg162415

[P]

Oh thanks for bringing that old thread up.
So it seems it's not just the expansion audio, it outputs the fully mixed APU + RP2C33 expansion audio along with the general I/O. And Nintendo seems to have reused the connector for the French NES' RGB output (they converted PAL to RGB only because it was cheaper than making a dedicated SECAM NES, and French TV-sets had RGB SCART by this point).

We still need a pinout though. Judging by ImATrackMan's picture the audio output pin is one of the outermost pins. One of the pins should be GND and another is probably +5 V, then there should be the 6 I/O pins leaving only one unknown pin out of the 10. Could it be battery status perhaps?

I guess I could whip together a test program, run the disk image via FDSStick and probe the pins someday...