Four player adapters

The NES Four Score and NES Satellite accessories allow four NES controllers to be connected to the NES's two controller ports. Controllers connected to this accessory are read using the same process as the standard controller. After the normal 8 reads from one port to get one controller data, 8 more are done to get another controller.

Note that the NES Four Score is not compatible with the convention widely used on the Famicom, which connects the 3rd and 4th players to data bit 1 instead of bit 0. The Famicom has its own adapters with different protocol, such as the Hori 4 Players Adapter. See Famicom Adapters below.

D3 and D4 are not connected on the Four Score, so accessories like the Zapper and Power Pad will not work with it. The Satellite has a separate "CTLR GUN" mode switch to permit use of the Zapper. (The Four Score has a similar switch for 2-player mode, but it merely disables the multi-tap feature, it still can't pass the extra lines.)

On both devices there are additional switches for turbo fire on the A and B button reports, which apply to all 4 ports.

Protocol

Input ($4016 write)

7  bit  0
---- ----
xxxx xxxS
        |
        +- Controller read strobe

This is used to strobe the OUT line of all 4 connected controllers at once.

This is normally written with bit 0 set, then again with bit 0 clear to poll the controllers before reading them out.

See: Controller reading

Output ($4016/$4017 read)

7  bit  0
---- ----
xxxx xxxD
        |
        +- Serial controller data

When the Four Score mode switch in the "4" position, it can be read like this:

1. Read $4016 D0 8x for the 8 bit report from controller #1.
2. Read $4016 D0 8x for the report from controller #3.
3. Read $4016 D0 8x for the signature: $10
4. Read $4017 D0 8x for the report from controller #2.
5. Read $4017 D0 8x for the report from controller #4.
6. Read $4017 D0 8x for the signature: $20

This allows 8 bits to be read from each of the 4 attached controllers. This is suitable for standard controllers which only report 8 bits on D0.

The signatures $10 and $20 are send most significant bit first. This can be used to detect the presence of the Four Score or Satellite.

The Four Score does not connect lines D3 or D4, so the Zapper is incompatible. The Satellite has a CTRL/GUN switch that can enable this, but not in 4-player mode. When the Four Score mode switch is in the "2" it will operate as if controllers #1 and #2 were directly connected, ignoring the other 2 ports and not producing a signature bit.

Famicom Adapters

Famicom expansion controllers attach extra controllers to D1 of $4016 and $4017. These may be used as players 3 and 4, though in 2-player games for the Famicom there is a convention to OR the D1 and D0 bits read to allow players to use an external controller as a substitute for the hard-wired ones.

Hori 4 Players Adapter

This adapter plugs into the Famicom 15-pin expansion port, and has 4 identical 15-pin ports on it to attach individual controllers. It has a mode switch with two settings, labelled "2" and "4".

Mode 2

More information is needed to verify this.

Presumably this is analogous to the Four Score's mode "2", but using D1 instead of D0. $4016 D1 reports bits directly from controller port 1, and $4017 D1 from port 2. Port 3 and 4 are not read, and there is no signature byte. Any extra bits read are simply an extended report from the port 1/2 devices.

Mode 4

This is a very similar protocol to the Four Score adapter described above, with two differences:

1. The serial stream comes through D1 rather than D0.
2. The signature bytes swap ports, with $20 read via $4016 and $10 read via $4017

In this mode the 4 Players Adapter actually adds 4 gamepads to the 2 built into the Famicom, potentially allowing 6-player games. However, its intended purpose seems to be offering 4-player support without requiring the hard-wired controllers.

Hardware

If you find yourself in the situation where you want to use the Four Score electrical interface for a project, but don't want to use up a Four Score, you can simply use six shift registers instead. Daisy-chain three shift registers together:

If using 4021s:

           IC1                 IC2                 IC3
          .-\/-.              .-\/-.              .-\/-.
       1A |1 16| Vcc       3A |1 16| Vcc      Vcc |1 16| Vcc
       nc |2 15| 1B        nc |2 15| 3B        nc |2 15| Vcc
NES P1 D0 |3 14| 1Sl       ZZ |3 14| 3Sl       YY |3 14| Vcc¹
      1Up |4 13| 1St      3Up |4 13| 3St      Vcc |4 13| Gnd²
      1Dn |5 12| nc       3Dn |5 12| nc       Vcc |5 12| nc
      1Lt |6 11| from ZZ  3Lt |6 11| from YY  Vcc |6 11| Gnd
      1Rt |7 10| NES CLK  3Rt |7 10| NES CLK  Vcc |7 10| NES CLK
      Gnd |8  9| NES OUT  Gnd |8  9| NES OUT  Gnd |8  9| NES OUT
          '----'              '----'              '----'

If using 74'165s:

         IC1                   IC2                 IC3
        .-\/-.                .-\/-.              .-\/-.
NES OUT |1 16| Vcc    NES OUT |1 16| Vcc  NES OUT |1 16| Vcc
NES CLK |2 15| Gnd    NES CLK |2 15| Gnd  NES CLK |2 15| Gnd
    1St |3 14| 1Up        3St |3 14| 3Up     ²Gnd |3 14| Vcc
    1Sl |4 13| 1Dn        3Sl |4 13| 3Dn     ¹Vcc |4 13| Vcc
     1B |5 12| 1Lt         3B |5 12| 3Lt      Vcc |5 12| Vcc
     1A |6 11| 1Rt         3A |6 11| 3Rt      Vcc |6 11| Vcc
     nc |7 10| from ZZ     nc |7 10| from YY   nc |7 10| Gnd
    Gnd |8  9| NES P1 D0  Gnd |8  9| ZZ       Gnd |8  9| YY
        '----'                '----'              '----'

For players 2 and 4, repeat the above, but change:

• NES P1 D0 becomes NES P2 D0
• 1xx becomes 2xx
• 3xx becomes 4xx
• IC3 pins denoted with ¹ and ² are swapped

Compatible games

From NesCartDB:

• Gauntlet II
• Greg Norman's Golf Power
• Harlem Globetrotters
• Indy Heat
• Kings of the Beach
• Kunio-kun no Nekketsu Soccer League
• M.U.L.E.
• Magic Johnson's Fast Break
• Monster Truck Rally
• NES Play Action Football
• A Nightmare on Elm Street
• Nintendo World Cup (and multicarts that contain it)
• R.C. Pro-Am II
• Roundball: 2-on-2 Challenge
• Smash T.V. (twin-stick for 2 players)
• Spot
• Super Jeopardy!
• Super Off Road
• Super Spike V'Ball
• Swords and Serpents
• Top Players' Tennis
• Wit's

Homebrew games:

• Double Action Blaster Guys becomes Quadruple Action Blaster Guys when Four Score is connected
• Micro Mages
• NESert Golfing
• Spacey McRacey
• Super PakPak

Tech demos:

• Eighty
• allpads