64JPX is a small interface designed to connect modern game pads to the Commodore 64 or Atari system. While some game controllers, notably the Sega Master System and Sega Genesis, are physically compatible with the C64 at the connector formfactor and pin level they are not fully electrically compatible. Depressing a button on a Sega controller connected to the C64 while also depressing a key on the keyboard exposes the C64's CIA chip to voltages it was not designed to handle making damage or failure likely.
This is because joysticks (which the game ports were intended to support) either pull the lines low (when active) or are an open connection (when inactive). This latter condition allows the lines to be pulled low by other sources (they keyboard for example). Sega gamepads, on the other hand, pull inactive lines HIGH. Now if you press a key on the keyboard with one of these devices plugged in, one source is pulling the line high while another I/O line (cross-connected through the keyboard) is trying to drag it down. This can put an extra strain on the CIA chip, as the circuit wasn't designed to deal with this kind of situation.
The 64JPX is not the first project of this type. Although the 64JPX offers many advanced features such as redefining the function of various buttons on the fly, a bare bones but effective game pad adapter was first detailed in the article Hard Tips: Build A Sega 'Game Pad' Adapter by Doug Cotton and Mark Fellows in Commodore World #5 details the basic schematics for just such an adapter.
64JPX not only allows you to safely connect Sega Genesis/MegaDrive, Nintendo SNES/NES joypads or other controllers to your retro system, it enhances game play with a number of on-the-fly selectable play modes.
The 64JPX comes in five basic versions:
RED: for users who only want to connect their Sega Genesis or MegaDrive controllers. Works with 3 and 6 button controllers. The Start button allows the different enhancement modes to be selected. The Sega controller directly connects to the 64JPX interface.
BLUE: for users who only want to connect their Nintendo controllers. Works with SNES and NES button controllers. The Start and Select buttons toggle the different enhancement modes available. You will need a pin-adapter to connect your Nintendo controller to the 64JPX interface.
PURPLE: a combination of RED and BLUE interfaces. The 64JPX interface auto-detects which controller is attached (Sega/SNES/NES) and configures itself for it. You will need a pin-adapter to connect your Nintendo controller to the 64JPX interface, or you can order the bundle which includes a modified controller.
ORANGE: a combination of the RED (Sega) interface and support for analog PC type controllers (DB15 connectors). The 64JPX interface auto-detects which controller is attached (Sega/PCanalog) and configures itself for it. You will need a pin-adapter to connect your PC analog controller to the 64JPX interface.
BLACK: budget version for users who only want to protect their C64 from Sega Master System, Genesis or MegaDrive controllers. Not all buttons work, and because the interface is 'chipless' there are no enhancement modes.
- Safely connect Sega MegaDrive/Genesis, Nintendo SNES/NES joypads, or other controllers
- Enhances game play with a number of on-the-fly selectable gaming enhancement modes
- Works out-of-the-box with Commodore, Atari and other compatible systems
- Provides diode protection to Commodore and Atari systems.
- Direct connect to Sega Genesis or Master System controllers.
- Via adapter accessory, 64JPX provides connection to other controllers such as SNES, NES, PC Wheels, flight yokes, 8-button joypads.
- Optional 1351 mouse pass-through port.
Default mode: In the default mode, button A is the regular "fire" or action button. Button A will work in your games exactly as the "fire" button on your conventional joystick works. Button B is a fast rapid fire button. Button C is a slow rapid fire button. Depending on your game either or both buttons will be of benefit as you blast aliens from the skies.
|Gamepad B||Rapid Fire 1||Up (Accelerate)||Waddle 1||Creep Left|
|Gamepad C||Rapid Fire 2||Down (Break)||Waddle 2||Creep Right|
|Gamepad Start||Mode Select A, B, or C|
Racing mode: This mode is primarily designed for racing games where pushing on the directional controller is supplemented by buttons for accelerating and decelerating. In these games, button A is your conventional "fire" button, usually hi/lo gear change. Button B is "up" or "accelerate"; whilst button C is "down" or "brake". Note: you can now "brake" at the same time as "accelerating", helpful in some games!
Waddle mode: This mode is primarily designed for sporting games, such as Summer Games and Decathlon, where waddling the joystick left and right caused your hero to run the 100m sprint in a new world record – that’s if you didn’t break your stick in the process!
In these games, button A is your conventional "fire" button, usually "jump" in hurdle events. Button B and C simulate the waddling of the joystick left and right. Several waddle modes and speeds are selectable depending on how you start the waddle. You may find some modes work better for your particular game than others.
|Waddle Mode||Button Combination||Bit Pattern||Speed|
|1||Right + Gamepad B||10,01,10,01,10,01,10,01||Fastest|
|2||Right + Gamepad C||10,01,10,01,10,01,10,01||Fast|
|3||Hold Gamepad B||00,11,00,11,00,11,00,11||Slow|
|4||Hold Gamepad C||00,11,00,11,00,11,00,11||Slowest|
Creep mode: This mode is primarily designed for platform games, such as Impossible Mission, Pitfall, etc, where you often need to creep up to an edge before jumping (or falling to your peril). In these games, button A is your conventional "fire" button; usually jump. Button B is "creep left"; whilst button C is "creep right". In creep mode your character will very slowly be "tapped" along in the request direction. The movement speed depends on the game played. The creep function can also be used to turn the character left/right with minimum risk of moving in that direction (and hence avoiding plummeting to your death!).