Ports and Connectors

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Front Panel

RCA Line In

These are standard RCA Line-In jacks, 2v P-P nominal.

Headphone Jack

Standard 1/8" stereo headphone jack.

SD Card

Standard SD Card slot using custom controller logic instantiated on an FPGA.

Joystick Ports

Joystick ports.png

The joystick ports, from left to right, are numbered 0,1,2,3.

  • Ports 0 and 1 may be electrically configured as 12 bit (S)NES style ports or as basic ATARI/Commodore with no support for paddles or analog joysticks.
  • Ports 2 and 3 (FMX only) are ATARI/C64 style ports and include analog inputs.
DB9 0-1 (S)NES 0-1 TTL 2-3 ATARI/C64
1 ignored UP UP
2 ignored DOWN DOWN
3 ignored LEFT LEFT
4 ignored RIGHT RIGHT
5 LATCH Button 1 POT-Y
6 DATA Button 0 BUTTON
7 +5 +5 +5
9 CLK Button 2 POT-X

Reset Switch

"Power" LED

The power LED is under software control.

Rear Panel

Power Switch

Just an ordinary rocker switch.


The power connector is a 12v center-positive 2.5mm barrel connector. The bare board should operate on as little as 500ma, but you should plan on more like 3A to cover adding a floppy drive, hard drive, etc.

PS/2 Keyboard and Mouse

  • PS/2 port 0 (Purple) -- nominal keyboard port
  • PS/2 port 1 (Green) -- nominal mouse port


The Video connector is DVI with digital and analog output suitable for use with passive VGA and HDMI adaptors.

Parallel Port (FMX)

IBM Standard DB25 EPP

Serial Port

The serial port on the U/U+ is a minimal 3-pin implementation. The serial port on the FMX is fully implemented.


  • The port on the left (closest to the serial port) is MIDI OUT.
  • The port on the right (closest to the RCA jacks) is MIDI IN.

Line Out

These are standard RCA Line-Out jacks, 2v P-P nominal.

U/U+ Internal

J5 (IDE)

Standard 44 Pin 2.5" laptop HDD IDC header.


Standard 10-pin J-TAG connector for reprogramming the FPGAs.

FMX Internal

J2 (Serial)

The 8-pin serial header follows the DTK/INTEL standard:

P2 (IDE)

Standard 44 Pin 2.5" laptop HDD IDC header.


Standard 10-pin J-TAG connector for reprogramming the FPGAs.


FLOPPY0 and FLOPPY1 are electrically standard 3.5" micro Floppy Disk Drive connectors (26 pins FPC Cable).

  • The internal drive is expected to be connected to FLOPPY0.


J-TAG interface for programming the TRINITY and UNITY FPGAs.

Side Panels

USB Debug Port

Mini USB (U/U+)

Micro USB (FMX)

Expansion Connector

Expansion Connector.png

Real Picture Expansion.png

Odd Description Even Description
3 CPU D0 (I/O) 4 CPU D1 (I/O)
5 CPU D2 (I/O) 6 CPU D3 (I/O)
7 CPU D4 (I/O) 8 CPU D5 (I/O)
9 CPU D6 (I/O) 10 CPU D7 (I/O)
11 GND 12 GND
13 CPU A0 14 CPU A1
15 CPU A2 16 CPU A3
17 CPU A4 18 CPU A5
19 CPU A6 20 CPU A7
21 CPU A8 22 CPU A9
23 CPU A10 24 CPU A11
25 CPU A12 26 CPU A13
27 CPU A14 28 CPU A15
29 CPU A16 30 CPU A17
31 CPU A18 32 CPU A19
33 CPU A20 34 CPU A21
35 CPU A22 36 CPU A23
37 GND 38 GND
39 EXP_RDY (I) 40 BUS_VPA (O)
41 BUS_R/Wn (O) 42 BUS_VDA (O)
43 SYS_RSTn (OC) 44 BUS_REQn (OC)
45 BUS_NMIn (OC) 46 BUS_ACKn (O)
47 EXP_CSn (O) 48 EXP_ACTn (OC)
49 EXP_CLK(O) 50 EXP_INTn(I)
51 GND 52 GND
53 +5V 54 +5V
55 +12V 56 EXP_LINE_IN_R (IA)
57 +12V 58 EXP_LINE_IN_L (IA)
59 +3V 60 +3V

(I/O) : Input/Output

(I) : Input

(O) : Output

(OC) : Output Collector (Wired Or) Bring down with OC Driver

(IA) : Input Analog (Audio Signal Input - Line Level)

Special Signals

  • EXP_RDY: This is the ready Line that will hold the bus thus stretching the cycle to allow slower devices to respond. Set to 1 to add delay, 0 for normal operation.
  • EXP_CSn: This is the Chip Select for the Expansion Card Zone: $AE:0000 - $AE:FFFF - for Compatibility reasons any I/O Card ought to be mapped into this area unless it requires more memory mapping.
  • EXP_ACTn: Bring this signal to ground for an expansion card to be recognized by the system.

Power Allocation per Rail

+3V3: Please don't use more than 500mA for the +3.3Volt Rail.

+5V: Please don't use more than 500mA for the +5Volt Rail. The system doesn't use a lot of +5V, but there are spurious needs for +5V rail when an HDD (spinning) is installed in the system.

+12V: The limit of current you can draw on the +12V is related to the power supply you are using for your machine. It is better to use that power supply to derive any other from.