Neo Geo Track Ball Games

Ape Cosplay · Jan 8, 2026

Yeah µPD4701s can be hard to source (altough you can find them in old serial mice at flea markets for $1), that's why a CPLD repro would be good.

Kujako · Jan 8, 2026

Ape Cosplay said:
Yeah µPD4701s can be hard to source (altough you can find them in old serial mice at flea markets for $1), that's why a CPLD repro would be good.

Only ones I can find are suspect (from China). Going the EPM7128SQC100 route is tempting, but a bit more complicated than I want to undertake right now.

pierpa86 · Jan 9, 2026

Ape Cosplay said:
In that case just follow the diagram I posted above and replace the CPLD by a µPD4701:

Wiring:

P2 UP (edge side) = pin 1 (Xa)
P2 DOWN (edge side) = pin 2 (Xb)
P2 LEFT (edge side) = pin 4 (Ya)
P2 RIGHT (edge side) = pin 5 (Yb)
CN4.7 = pins 3 (RESET X) & 6 (RESET Y)
CN4.6 = pin 14 (!X /Y)
P1 UP (board side) = pin 16 (D0)
P1 DOWN (board side) = pin 17 (D1)
P1 LEFT (board side) = pin 18 (D2)
P1 RIGHT (board side) = pin 19 (D3)
P1 A (board side) = pin 20 (D4)
P1 B (board side) = pin 21 (D5)
P1 C (board side) = pin 22 (D6)
P1 D (board side) = pin 23 (D7)

Lastly tie pins 13 (U/!L) and 15 (!CS) to ground.
(And don't forget the power pins OFC).

Now if you don't want to build a solution that would plug in place of a real SIT board disregard the edge side and simply wire the trackball directly to the µPD4701.

You'd need to amplify the signal coming from CN4.1, I can have a look at the transistor reference used on the original SIT board.

Dude thanks for this pinout, i'm a bit confused on this part:
Why p2 ?

P2 UP (edge side) = pin 1 (Xa)
P2 DOWN (edge side) = pin 2 (Xb)
P2 LEFT (edge side) = pin 4 (Ya)
P2 RIGHT (edge side) = pin 5 (Yb)

I have to connect trackball directly on µPD4701 on this pins ? :

Trackball	µPD4701
X Clock	pin 1 (XA)
X Direction	pin 2 (XB)
Y Clock	pin 4 (YA)
Y Direction	pin 5 (YB)

Ape Cosplay · Jan 10, 2026

Hey,

What I meant is on the SIT board Xa for instance comes from P2 UP on the JAMMA (cab side).
You can totally wire the trackball directly to the 4701.

Maybe I should take a pic of the SIT board. On one side it connects to the JAMMA inside the cab, on the other side it connects to the JAMMA of the slot.

Kujako · Jan 10, 2026

Ape Cosplay said:
Hey,

What I meant is on the SIT board Xa for instance comes from P2 UP on the JAMMA (cab side).
You can totally wire the trackball directly to the 4701.

Maybe I should take a pic of the SIT board. On one side it connects to the JAMMA inside the cab, on the other side it connects to the JAMMA of the slot.

Pics always help.

Tracked down my trackball, still looking for my stash of really old mice to see if there's a UPD4701 I can steal. I did order some from china, but assuming they're fake. Fingers crossed they're just rebuilt (but I'll need to figure out a way to test them on a bread board, can use an oscilloscope I figure).

nauman · Jan 10, 2026

After reading my own post again I realized that it might have left some important information in the dark for someone who aims to create a replica of the trackball part of the SIT-board. In case it helps someone out, here are some more in-depth information:

Made a few tables with the perspective of how the BIOS/MVS unit expect the values to arrive. Some confusion might arise from the fact that all units does not even have the "trackball X / Y select" pin exposed. If you are planing to use a MVS without the DB-15 connections, you might have to create a trace from the NEO-D0 to the "SIT-board".

Name	All	MV2F	MV1FZ*	SIT-IC-OUTPUT	Purpose
P1 Up	JAMMA 18	1P DB-15 Pin 15	-	Trackball X / Y Bit 0	8-bit movement value
P1 Down	JAMMA 19	1P DB-15 Pin 7	-	Trackball X / Y Bit 1	8-bit movement value
P1 Left	JAMMA 20	1P DB-15 Pin 14	-	Trackball X / Y Bit 2	8-bit movement value
P1 Right	JAMMA 21	1P DB-15 Pin 6	-	Trackball X / Y Bit 3	8-bit movement value
P1 Button A	JAMMA 22	1P DB-15 Pin 13	-	Trackball X / Y Bit 4	8-bit movement value
P1 Button B	JAMMA 23	1P DB-15 Pin 5	-	Trackball X / Y Bit 5	8-bit movement value
P1 Button C	JAMMA 24	1P DB-15 Pin 12	-	Trackball X / Y Bit 6	8-bit movement value
P1 Button D	JAMMA 25	1P DB-15 Pin 4	-	Trackball X / Y Bit 7	8-bit movement value
P2 Button A	JAMMA Z	2P DB-15 Pin 13	-	-	Left A
P2 Button B	JAMMA a	2P DB-15 Pin 5	-	-	Left B
P2 Button C	JAMMA b	2P DB-15 Pin 12	-	-	Right A
P2 Button D	JAMMA c	2P DB-15 Pin 4	-	-	Right B

Name	MV2F	MV1FZ*	SIT-IC-INPUT	Optional for trackball only?
P1 Output 1	1P DB-15 Pin 10	NEO-D0 Pin 4	Trackball X / Y select	No
P1 Output 2	1P DB-15 Pin 2	NEO-D0 Pin 5	Data	Yes
P1 Output 3	1P DB-15 Pin 9	NEO-D0 Pin 6	Clock	Yes
P2 Output 1	2P DB-15 Pin 10	NEO-D0 Pin 7	Latch	Yes
P2 Output 2	2P DB-15 Pin 2	NEO-D0 Pin 8	Card dispenser	Yes
P2 Output 3	2P DB-15 Pin 9	NEO-D0 Pin 9	Air Jet	Yes

BIOS Registry – Trackball

Memory	Purpose	Source	Used by Irritating Maze
0x10FE02	Previous frame	0x10FE03	No
0x10FE03	Current frame	REG_P1CNT (0x300000)	No
0x10FE04	Delta (current - previous)	0x10FE03 - 0x10FE02	Yes
0x10FE05	Cache high 4 bit delta for direction	(0x10FE03 & 0xF0) - 0x10FE05	No

BIOS Registry – Buttons

Memory	Purpose	Structure	Source	Used by Irritating Maze
0x10FD94[0-5]	"Joypad/Joystick state"	Bit 7 = P2 D Bit 6 = P2 C Bit 5 = P2 B Bit 4 = P2 A Bit 3 = X dir(+) Bit 2 = Y dir(-) Bit 1 = Y dir(+) Bit 0 = Y dir(-)	7-4 = REG_P2CNT (0x340000)[BR]3-0 = BIOS calculation	No
0x10FD9A[0-5]	"Joypad/Joystick state"	Same as above	Copy of 0x10FD94	Yes

pierpa86 · Jan 12, 2026

P2 Button A	JAMMA Z	2P DB-15 Pin 13	-	-	Left A
P2 Button B	JAMMA a	2P DB-15 Pin 5	-	-	Left B
P2 Button C	JAMMA b	2P DB-15 Pin 12	-	-	Right A
P2 Button D	JAMMA c	2P DB-15 Pin 4	-	-	Right B

Talking this buttons, are they used in game ?

What is their purpose in the game?

Testing in game I understand that A is used but I don't understand what B is used for and why having two A and two B, I see that Left A and Right A in game do the same thing.

twistedsymphony · Jan 12, 2026

pierpa86 said:
Talking this buttons, are they used in game ?
What is their purpose in the game?

pierpa86 said:
Testing in game I understand that A is used but I don't understand what B is used for and why having two A and two B, I see that Left A and Right A in game do the same thing.

it's to simplify wiring and maintenance even though they have the same function left and right by having independent wiring if one button fails it doesn't take out the other button and they can be independently tested in game test mode.

pierpa86 · Jan 12, 2026

Seems we dont need B and double A buttons on dedicated trackball pad.
We just need one A and Start

twistedsymphony · Jan 12, 2026

seems strange they would put it on the control panel if it's not used.

pierpa86 · Jan 12, 2026

I'm trying to understand better the part about:

CN4.7 = pins 3 (RESET X) & 6 (RESET Y)
CN4.6 = pin 14 (!X /Y)

CN4.6 is OUT1 but if we take this signal from 1P DB-15 Pin 10 its hex inverted from 74ls06 so maybe ca be a problem.

CN4.7 reset pin is from NEO-SDR-T pin 70, and on NEO-D0 pin 20 ?
Its not on side connector of MV2F and not on the DB15

Neo-Alec · Jan 13, 2026

twistedsymphony said:
seems strange they would put it on the control panel if it's not used.

For the future trackball games of course!

Kujako · Jan 15, 2026

Neo-Alec said:
For the future trackball games of course!

Not gonna lie, I was always surprised there wasn't a track ball enabled golf title at some point à la Golden Tee. Or League Bowling 2.

nauman · Jan 16, 2026

pierpa86 said:
I'm trying to understand better the part about:

CN4.7 = pins 3 (RESET X) & 6 (RESET Y)
CN4.6 = pin 14 (!X /Y)

I believe the reset signal is unnecessary for a trackball-only implementation. It is very likely used to reset other parts of the SIT-board and since the trackball is always read as an offset compare to previous frame, it really doesn't matter if the first value is very large at the first frame/read.
Just for information, this reset signal is shared across the whole board and can be source from any IC/pin, although RESET and RESETP is not the same so use the system wide RESET and react when the this line goes low (reset is in action when low).

Regarding the inverter for x/y, it is just a matter of matching the trackball output to the correct version. If it is the wrong way around, like spinning left/right is up/down, then just swap the wires

Kujako · Jan 21, 2026

Looks like back in '88 Logitech was already on custom ICs.

Know I have more old mice around here, the hunt continues. If anyone knows of a make and model that has a UPD4701 in it please share.

nauman · Jan 23, 2026

So this is what $25 gets you from Aliexpress, an amazing ps/2 trackball

Let us see if I can convert this to a Neo Geo trackball with a FPGA/CPLD this weekend!

Kujako · Jan 26, 2026

~$4 from Aliexpress gets you a couple suspect UPD4701s (breadboard and SBC not included). Definitely not "new", the shiny legs are indicative of them being rebuilt. Not sure there's even real. Will have to see if I can cobble together a quick test circuit on the breadboard (any help with this would be welcome, brain not working gud right now).

bodgit · Jan 26, 2026

If this uses the same technique as for reading a spinner then I now have a working circuit built using 74xx logic, obviously it needs to be doubled to read both the X and Y axis on a trackball or mouse.

I did have a test sketch using an Arduino that would bit-bang a uPD4701 with a trackball attached to prove it worked. I'll see if I can find it.

Kujako · Jan 26, 2026

bodgit said:
If this uses the same technique as for reading a spinner then I now have a working circuit built using 74xx logic, obviously it needs to be doubled to read both the X and Y axis on a trackball or mouse.

I did have a test sketch using an Arduino that would bit-bang a uPD4701 with a trackball attached to prove it worked. I'll see if I can find it.

That'd be appreciated, having a hard time even finding pinouts for these things.

bodgit · Jan 27, 2026

Kujako said:
That'd be appreciated, having a hard time even finding pinouts for these things.

I had since reinstalled my laptop so I had to dig through the backup I made before I wiped it. Here's what I found:

C:

// Basic NEC µPD4701AC test code
//
// Wire up the Arduino pins to the chip based on the comments below.
// You will use digital pins 2-11 as inputs and analog pins 0-4 as outputs.
//
// In addition:
// * Use 10KΩ pullup resistors on the three button inputs
// * Use 4.7KΩ pullup resistors on the four X1/X2/Y1/Y2 inputs

void setup() {
  Serial.begin(9600);
 
  // D0-D7
  pinMode(2, INPUT);
  pinMode(3, INPUT);
  pinMode(4, INPUT);
  pinMode(5, INPUT);
  pinMode(6, INPUT);
  pinMode(7, INPUT);
  pinMode(8, INPUT);
  pinMode(9, INPUT);
 
  // !SF
  pinMode(10, INPUT);
 
  // !CF
  pinMode(11, INPUT);
 
  // Reset X & Y
  pinMode(A0, OUTPUT);
  pinMode(A1, OUTPUT);
  digitalWrite(A0, LOW);
  digitalWrite(A1, LOW);
 
  // !CS
  pinMode(A2, OUTPUT);
  digitalWrite(A2, HIGH);
 
  // X/Y
  pinMode(A3, OUTPUT);
  digitalWrite(A3, LOW);
 
  // U/L
  pinMode(A4, OUTPUT);
  digitalWrite(A4, LOW);
}

byte readByte() {
  byte b;
  for (int i = 0; i < 8; i++) {
    b |= digitalRead(i+2) << i;
  }
  return b;
}

void loop() {
  byte left, middle, right;
  uint16_t x, y;

  // Read CF & SF interrupt pins
  if (!(digitalRead(10) && digitalRead(11))) {

    // CS low
    digitalWrite(A2, LOW);

    // X counter low byte (X/Y=0 U/L=0)
    digitalWrite(A3, LOW);
    digitalWrite(A4, LOW);
    x = readByte();
 
    // X counter high byte (X/Y=0 U/L=1)
    digitalWrite(A3, LOW);
    digitalWrite(A4, HIGH);
    x |= uint16_t(readByte()) << 8;

    // Pick out the button status from the upper nibble of the upper byte
    left = x & 0x4000 ? 1 : 0;
    right = x & 0x2000 ? 1 : 0;
    middle = x & 0x1000 ? 1 : 0;

    // Mask out the upper nibble of the upper byte
    x &= 0xfff;

    // Y counter low byte (X/Y=1 U/L=0)
    digitalWrite(A3, HIGH);
    digitalWrite(A4, LOW);
    y = readByte();

    // Y counter high byte (X/Y=1 U/L=1)
    digitalWrite(A3, HIGH);
    digitalWrite(A4, HIGH);
    y |= uint16_t(readByte() & 0xf) << 8; // Mask out the button status this time

    Serial.print("L=");
    Serial.print(left);
    Serial.print(" M=");
    Serial.print(middle);
    Serial.print(" R=");
    Serial.print(right);
    Serial.print(" X=");
    Serial.print(x);
    Serial.print(" Y=");
    Serial.println(y);
    
    // CS high again
    digitalWrite(A2, HIGH);
  }
}

I think you will need the datasheet to know what the pinout on the chip is.

Neo Geo Track Ball Games

Ape Cosplay

Kujako

pierpa86

Ape Cosplay

Kujako

nauman

pierpa86

twistedsymphony

Enlightened

pierpa86

twistedsymphony

Enlightened

pierpa86

Neo-Alec

Kujako

nauman

Kujako

nauman

Kujako

bodgit

Kujako

bodgit