Tell me more ×
Arqade is a question and answer site for passionate videogamers on all platforms. It's 100% free, no registration required.
up vote 7 down vote favorite

How can it multiplex four controllers onto two controller ports? Would it be possible to extend it further with three devices?

share|improve this question
Just a guess: I would think it would send a special code before transmitting each button press to differentiate the controllers, and the games that were designed to use it would be looking for and take advantage of said code. – Matthew Read Jun 23 '11 at 16:22
1  
Unless you're thinking of some kind of homebrew application, there would be little point in chaining them together, given that the device only works with specific games that were designed for it as @Matthew mentioned. You'd probably just be sending more "Player 3" and "Player 4" signals ... and if it did send "Player 5" and "Player 6", there'd be no games to read them. – Dave DuPlantis Jun 23 '11 at 17:59
1  
The wiki (en.wikipedia.org/wiki/NES_Four_Score) confirms: "It allows four-player gameplay on games that supported it". Also I wouldn't be surprised if it used some bit manipulation which then the proper game could easily and quickly check i.e. if bit 12 is a 1, then we're player 3. – Robb Jun 23 '11 at 18:28
This is not a question about gaming, nor a problem that gamers need solved. This is a question about electrical engineering. Off Topic – StrixVaria Jun 28 '11 at 16:45
1  
I thought it fit under "Game-specific hardware and utilities". – Jens Björnhager Jun 29 '11 at 1:25

1 Answer

up vote 3 down vote accepted

This link may help you sort out some of the details. The two joypads connect to the NES through a form of serial communication. The controller sends a synchronized 8-Bits across the #7 pin connector.

The value of the button that is pressed is encoded within 8 bits that are communicated and synchronized with a clock signal sent across the #2 pin.

When the four score is connected, the four score sends a 24-bit stream across both controller #7 pin channels. The first bytes on each line correspond with controllers 1 & 2's buttons. The second byte across both lines corresponds to controllers 3 & 4 and the last byte is an "ID" byte which I'm not entirely sure was used for.

share|improve this answer
Ah, so the protocol changes completely in 4-player mode? Perhaps this is the reason you have to manually switch between 2- and 4-player mode on the device. – Jens Björnhager Jun 29 '11 at 1:33
Yes, that's correct. The protocol is different and your assumption is correct. Set the device to four player and it communicates in the method that I described above. Set it to two player and it passes the inputs from the #1 and #2 controllers back to the NES, unchanged. – RLH Jun 29 '11 at 11:57

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.