Controller port pinout

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                            +----------< $4017.D3          
                            | +--------< D0                
                            | | +------> OUT0             +------------------ GND
                            | | | +----> CLK              | +--------------<> AUDIO
                            | | | | +--< $4017.D4         | |           +---< D0
        .-                  | | | | |                     | |           |
 GND -- |O\              +-------------+               +-------------------+
 CLK <- |OO\ -- +5V       \ O O O O O /                 \ O O O O O O O O /
 OUT <- |OO| <- D3         \ O O O O /                   \ O O O O O O O /
  D0 -> |OO| <- D4          +-------+                     +-------------+
        '--'                 |   |                         |     |     |
                             |   +------ GND               |     |     +---- +5V
                             +---------- +5V               |     +---------: OUT0
                                                           +---------------> CLK
     NES port           9 pin famiclone port               15 pin famiclone port     
 * Directions are relative to the jack on the from of console
 * $4017.D4/$4017.D4 are available only at port 2 in consoles equipped only with 2x9pin ports
 * AUDIO might not always be available

The 15-pin connector is a subset of the standard Famicom expansion port.

Protection Diodes

Some PAL region systems have a set of diodes on the inside of the controller port which make it incompatible with NTSC controllers.[1]

+5V --|>|-- jack
 D3 --|>|-- jack
 D4 --|>|-- jack
 D0 --|>|-- jack
OUT --|<|-- jack
CLK --|<|-- jack

With these diodes, the OUT and CLK lines have to be pulled high by the controller, or else the controller can't receive these signals. See: Standard controller: PAL

These diodes are also present on the ports of the Four Score (NESE-034) accessory for this region.

Super NES

The FC Twin NES/SNES combo clone uses Super NES controllers, whose pinout is as follows:[2]

 1 [oooo|ooo) 7  1:+5V  2:Clk  3:Out  4:D0  5:D1  6: I/O  7:Gnd

An adapter to use Super NES controllers on an NES (or NES controllers on an FC Twin) could be constructed as follows (leaving D3 and D4 unconnected):

 GND -- |7\
 CLK <- |21\ -- +5V
 OUT <- |3o| -- (D3)
  D0 -> |4o| -- (D4)
  1. Buy two controller extension cables, one for NES and one for Super NES, and cut them apart. Strip the cut ends to reveal a small amount of bare wire.
  2. Using inline splice technique, wrap each wire from one cable with the corresponding wire from the other cable.
  3. With solder and a soldering iron, glue each wrapped pair together.
  4. With electrical tape, wrap each joint to insulate it from the other wires.
  5. Apply heat shrink around the whole assembly.


  • The signal read by the CPU is logically inverted from the signal input on the D0-4 lines. A low voltage on D0 will be read as a 1 bit from $4016/4017.
  • CLK will be low during reads from the CPU, then immediately return to high. This rising edge transition is used to clock the shift register inside the standard controller.
  • OUT is a signal latched and held from the last CPU write to $4016:0. For standard controller reads, the program will write a 1 to load the shift register, then return to 0 before reading the results.

Hardware design

  • Famicom and NES controllers use single 4021 8-step shift register for serial transmission (pressed button is shorted to GND by low-resistance rubber pad; VCC pull-ups are inside 4021)
      | -----+
 BTN--+----- +-- GND
      | -----+
  • Cascading input is connected to GND, which results in returning 1 for reads greater than 8 (in contrary to most blob pads, where it returns 0).
  • Rare model of non-blob IQ502 famiclone joypad uses UM6582 chip which aggregates both serial encoder and square wave generator (for turbo buttons)
  • Most famiclone pads use glob chip which integrates both serial encoder and turbo generator
  • Pressing TURBOA (or TURBOB) causes short of A (or B) to the square wave generated by chip (or blob).
           TURBO A
 TURBO >----'  '--+
            ----  |
   GND -----'  '--+----> !A
  • Some joypads contains also buttons C and TURBO C (whose acts as pressing buttons A and B together); The SMD contact for that button contains three signals
  • SNES joypads contain two 4021 or two WR545 chips chained together
           ,---v---.                 WR545#1  WR545#2  
       d0->|01   14|--VCC         d0  B       A
     DOUT<-|02   13|<-d1          d1  Y       X
       d4->|03   12|<-d2          d2  SEL     TL
       d5->|04   11|<-d3          d3  ST      TR
       d6->|05   10|<-DIN         d4  U       -
       d7->|06   09|<-CLOCK       d5  D       -
      GND--|07   08|<-STROBE      d6  L       -
           +-------+              d7  R       -

See Also


  1. Forum post: explaining PAL controller diodes and their function.
  2. Schematics, Ports, and Pinouts.