Controllers

The SNES has 2 controller ports on the front of the unit, and an "expansion port" on the bottom. Little is known about the expansion port.

A number of peripherals could be plugged into the controller ports:

• Joypads
• The Multitap: Also know as the MP5, into which up to 4 joypads may be plugged.
• Mouse: SNES Mouse with 2 buttons.
• Super Scope: A bazooka-like light gun.
• Konami Justifier: A normal style gun into which a second gun could be plugged.
• Soundware: A device to control a CD player for external audio.
• NTT Modem: Used for online horse racing.

There may be others, these are just the ones I know anything about.

General Info

The controller ports of the SNES has 7 pins, see Ports & Pinouts for the layout.

Latch is written through bit 0 of register $4016. Writing 1 to this bit results in Latch going to whatever state means 'latch' to a joypad.

Clock of Port 1 is connected to the 'read' signal of $4016, in that reading $4016 causes Clock to transition. Data1 and Data2 are then read, and Clock transitions back (at this point, the pad is expected to stick its next bits of data on Data1 and Data2). Clock of Port 2 is connected to $4017.

Data1 and Data2 are read through bits 0 and 1 (respectively) of $4016 and $4017 (for Ports 1 and 2, respectively). Thus, you must read both bits at once, you can't choose to read only Data1 and leave Data2 for later.

IOBit is connected to the I/O Port (which is accessed through registers $4201 and $4213). Port 1's IOBit is connected to bit 6 of the I/O Port, and Port 2's IOBit is connected to bit 7. Note that, since bit 7 of the I/O Port is connected to the PPU Counter Latch, anything plugged into Port 2 may latch the H and V Counters by setting IOBit to 0.

Auto Joypad Read, when enabled by bit 0 of $4200, effectively does the following (in pseudo-ASM):

LDA $4212
ORA #$01
STA $4212  ; pretend it's writable

LDA #$01
STA $4016
; There may be a delay here
STZ $4016

LDX #$0010
loop:
    LDA $4016
    REP #$20
    LSR
    ROL $4218
    LSR
    ROL $421C
    SEP #$20

    LDA $4017
    REP #$20
    LSR
    ROL $421A
    LSR
    ROL $421E
    SEP #$20
    
    DEX
BNE loop

LDA $4212
AND #$7E
STA $4212  ; pretend it's writable again

Open Port

If nothing is plugged into a port (or the thing plugged in doesn't connect to the pin), the SNES will read zeros from Data1 and Data2.

Joypads

The joypads return 16 bits of data out Data1, then one bits until latched again. The data is:

byetUDLRaxlr0000

b/y/a/x/l/r are the similarly named buttons. 'e' is select. 't' is start. U/D/L/R are the pad directions. Note that the standard joypad can only return either U or D set, and either L or R set. Some games will crash or exhibit other odd behavior if both U and D and/or both L and R are set. Data2 is not even connected, nor is IOBit.

Mouse

The mouse returns 32 bits of data out Data1, and 1 bits thereafter. The data is:

00000000rlss0001 YyyyyyyyXxxxxxxx

l/r are the two mouse buttons. 'ss' are the "speed bits", which are incremented mod 3 if Clock cycles while Latch is active. Y/X are the direction bits (set is up/left), and yyyyyyy/xxxxxxx are the distance traveled in the appropriate direction. Supposedly, the 'speed bits' may not match the internal speed setting when the mouse first receives power. The speed setting controls the delta curve of the mouse, with 0 giving a flat curve and 2 giving the greatest delta response. Data2 and IOBit are presumably not connected, but this is not known for sure.

Mouse Supporting Games

This list isn't 100% complete, but the games below contain the SHVC mouse BIOS, an example of some of the strings in the games are shown below of which is below. Game names are based on the No-Intro names.

START OF MOUSE BIOS
NINTENDO SHVC MOUSE BIOS Ver1.10
END OF MOUSE BIOS

Some games have a modification of a certain BIOS version. They are marked with a "mod" in the list below. Nintendo had the developers to mark up modified versions with an alternate ASCII code at the end of the BIOS:

MODIFIED FROM SNES MOUSE BIOS Ver1.xx

Super Scope

The Super Scope returns 8 bits of data out Data1, and 1 bits thereafter. The data is:

fctp00on

'f' is Fire, 'c' is Cursor, 't' is Turbo, 'p' is Pause, 'o' is Offscreen, and 'n' is Noise.

The Super Scope has two modes of operation: normal mode and turbo mode. The current mode is controlled by a switch on the unit, and is indicated by the 't' bit. Note however that the 't' bit is only updated when the Fire button is pressed (i.e. the 'f' bit is set). Thus, when you turn turbo on the 't' bit remains clear until you shoot, and similarly when turbo is deactivated the bit remains set until you fire.

In either mode, the Pause bit will be set for the first strobe after the pause button is pressed, and then will be clear for subsequent strobes until the button is pressed again. However, the pause button is ignored if either cursor or fire are down(?).

In either mode, the Cursor bit will be set while the Cursor button is pressed.

In normal mode, the Fire bit operates like Pause: it is on for only one strobe. In turbo mode, it remains set as long as the button is held down.

When Fire/Cursor are set, Offscreen will be set if the gun did not latch during the previous strobe and cleared otherwise (Offscreen is not altered when Fire/Cursor are both clear).

Noise is set if there is interference in the infrared transmission from the Scope to the receiver.

If the Fire button is being held when turbo mode is activated, the gun sets the Fire bit and begins latching. If the Fire button is being held when turbo mode is deactivated, the next poll will have Fire clear but the Turbo bit will not be updated until the next fire (i.e. FcTp => turbo off => fcTp, not fctp).

The PPU latch operates as follows: When Fire or Cursor is set, IOBit is set to 0 when the gun sees the TV's electron gun, and left a 1 otherwise. Thus, if the SNES also leaves it one (bit 7 of $4201), the PPU Counters will be latched at that point. This would also imply that bit 7 of $4213 will be 0 at the moment the Super Scope sees the electron gun.

Since the gun depends on the latching behavior of IOBit, it will only function properly when plugged into Port 2. If plugged into Port 1 instead, everything will work except that there will be no way to tell where on the screen the gun is pointing.

When creating graphics for the Super Scope, note that the color red is not detected. For best results, use colors with the blue component over 75% and/or the green component over 50%.

Data2 is presumably not connected, but this is not known for sure.

Super Scope Supporting Games

This list isn't 100% complete, but the games below contain the SHVC Super Scope BIOS, an example of some of the strings in the games are shown below of which is below. Game names are based on the No-Intro names.

START OF SCOPE BIOS
NINTENDO SHVC SCOPE BIOS Ver1.00
END OF SCOPE BIOS

Konami Justifier

The Justifier returns 48 bits of data out Data1. Presumably it returns one bits after (if so, it really only returns 32 bits), but this is not known. The data is:

0000000000001110 01010101TtSsl000 1111111111111111

T/t are the trigger states for guns 1 and 2. S/s are the start button states for guns 1 and 2. 'l' indicates which gun was connected to IOBit: 1 means gun 1, 0 means gun 2. Note that 'l' toggles even when gun 2 is not connected.

IOBit is used just like for the Super Scope. However, since two guns may be plugged into one port, which gun is actually connected to IOBit changes each time Latch cycles. Also note, the Justifier does not wait for the trigger to be pulled before attempting to latch, it will latch every time it sees the electron gun. Bit 6 of $213F may be used to determine if the Justifier was pointed at the screen or not.

Data2 is presumably not connected, but this is not known for sure.

MultiTap / MP5

The MP5 plugs into one Controller Port on the SNES (typically Port 2), and has 4 ports for controllers to be plugged into it (labeled 2 through 5). It also has an override switch which makes it pass through Pad 2 and ignore everything else.

If IOBit is 1, Clock is passed through to Pad 2 and Pad 3, Data1 is connected to Data1 on Pad 2, and Data2 is connected to Data1 on Pad 3. If IOBit is 0, Pads 4 and 5 are used instead of 2 and 3, respectively. In either case, Latch is passed through to all pads, and IOBit is presumably not passed through at all.

Note that Clock is only passed through to the pads that are actually being passed through. Thus, you can read the first two pads (or let Auto-Joypad Read do it), then toggle IOBit and read the other two pads manually. Most games requiring more than 3 players do exactly this.

Also note that there is nothing preventing the MP5 from functioning perfectly when plugged in to Port 1, except that the game must use bit 6 of $4201 instead of bit 7 to set IOBit and must use the Port 1 registers instead of the Port 2 registers. With 2 MP5 units, one could actually create an 8-player game!

When Latch is active, 1s will be read from Data2 and 0s from Data1. This is sometimes used to detect the presence of an MP5 unit. The override switch disables this behavior.

((There is some confusion on this point: according to nintendo's book2, Data1 SHOULD keep returning normal controller data; that is, stuck on the first bit (B button) since shift-register is stopped when "latch is active". However, according to this document by Jim Christy, the first bit of controller data is not loaded onto the Data line until the falling edge of the latch pulse: presumably, therefore, the console can start the latch pulse, wait a bit, read the data lines to detect an MP5, end the latch pulse, wait a bit longer, then start the first clock pulse and sample the first bit of controller data.)).

There are reports that the MP5 does not react immediately when IOBit is transitioned from 0 to 1. Thus, reading 2&3 then 4&5 will probably work better than vice versa.

Multi-Tap Supporting Games

This list hasn't been checked to be 100% complete, but every game below contains the multi-tap BIOS, an example of some of the strings in the games are shown below of which is below. Game names are based on the No-Intro names.

START OF MULTI5 CONNECT CHECK
NINTENDO SHVC MULTI5 CONNECT CHECK Ver1.00
END OF MULTI5 CONNECT CHECK
START OF MULTI5 BIOS
NINTENDO SHVC MULTI5 BIOS Ver2.00
END OF MULTI5 BIOS

Soundware

TODO

NTT Modem

TODO

Game Multi-Tap and Mouse BIOS versions determined by Matthew Callis.