Famicom expansion port pinout

==Pinout of 15-pin Famicom expansion port==

             /\
            |   \
        GND | 01  \
            |   09 | /OE for joypad 2
      SOUND | 02   |
            |   10 | out 2 ($4016.2)
        IRQ | 03   |
            |   11 | out 1 ($4016.1)
joypad 2 D4 | 04   |
            |   12 | out 0 ($4016.0, Strobe)
joypad 2 D3 | 05   |
            |   13 | joypad 1 D1
joypad 2 D2 | 06   |
            |   14 | /OE for joypad 1
joypad 2 D1 | 07   |
            |   15 | +5V
joypad 2 D0 | 08  /
            |   /
             \/

Signal descriptions

Digital inputs to the Famicom

Joypad 1 D1, Joypad 2 D0…D4

Digital outputs from the Famicom

Out 0, 1, 2; /OE for both joypads

Open-collector bidirectional

IRQ

Analog outputs

SOUND (before expansion audio is mixed in)