Interactive Connector Diagram
Click or tap any pin in the diagram below to inspect its signal assignment, electrical specification, and wire colour standard.
Click any pin to view its signal assignment, electrical spec, and wire colour.
Used in Retro Machine Hubs
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Connector Specifications
Edge Pitch
2×12 (0.156" / 3.96mm pitch; Top Row = Numbers 1–12, Bottom Row = Letters A–N omitting G, I)
Parallel Port
Bottom Row Pins C, D, E, F, H, J, K, L = PB0 to PB7 (CIA #2 on C64/128; VIA on VIC-20/PET)
Power Pins
Top Pin 2 = +5V DC (100mA) | Top Pins 10 & 11 = 9V AC (C64/C128/VIC-20 CR only!)
PET CB2 Audio
Bottom Pin M = CB2 Shift-Register Audio Out on Commodore PET!
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| Top 1 & 12 / Bot A & N | GND (0 V) | GND | 0 V Digital Ground on all four corner fingers (1, 12, A, N) | Black (GND) |
| Top 2 | +5.0V DC (C64/VIC/128) | Pwr | +5.0 V DC Logic Supply (powers Wi-Fi modems! Note: Video Out on PET) | Red (+5V) |
| Top 3 | /RESET | I/O | Active-Low System Reset (ground briefly to reset computer!) | Orange |
| Top 4 & 5 | CNT1 (4) & SP1 (5) | I/O | CIA #1 Serial Shift Register Clock & Data (Top 5 = DIAG Monitor on PET!) | Yellow |
| Top 6 & 7 | CNT2 (6) & SP2 (7) | I/O | CIA #2 Serial Shift Register Clock & Data (used in C128/C64 Burst mod) | Green |
| Top 8 & 9 | /PC2 (8) & ATN/PA3 (9) | I/O | Pin 8 = CIA2 Handshake Out (/PC2) | Pin 9 = Serial ATN In | Blue |
| Top 10 & 11 | 9.0V AC (C64 / C128) | Pwr | 9.0 V AC Transformer Output (100 mA max — NOT present on PET or SX-64!) | Purple (9V AC) |
| Bot B | /FLAG2 (CA1 / CB1) | In | CIA2 /FLAG2 Handshake / RS-232 Received Data Bit Input! | White (RS-232 RX) |
| Bot C – L | PB0 – PB7 (8-Bit Port) | I/O | C=PB0, D=PB1, E=PB2, F=PB3, H=PB4, J=PB5, K=PB6, L=PB7 | 8-Bit Parallel Bus |
| Bot M | PA2 (C64 TX) / CB2 (PET) | Out | C64/128: CIA2 PA2 (RS-232 TX Out) | PET & VIC-20: VIA CB2 (PET Sound Out!) | Green (TX / PET Audio) |
Connecting a User Port Wi-Fi Modem & External Reset Button
Across the PET, VIC-20, C64, SX-64, and C128, the 24-contact User Port is the hobbyist's favorite interface: Bottom Row Pins C through L provide an 8-bit parallel port (PB0–PB7) directly from 6526 CIA #2 ($DD01 on C64/C128) or 6522 VIA ($9110 on VIC-20 / $E840 on PET) — used for ESP8266/ESP32 Wi-Fi modems, 4-player joystick adapters, parallel 1541 SpeedDOS cables, and EPROM programmers!
- External Reset Pushbutton: Wire a momentary normally-open pushbutton between Top Pin 3 (/RESET) and Top Pin 1 (GND) for a zero-solder external reset switch on any C64, VIC-20, or C128!
- User Port Wi-Fi Modem (StrikeLink / Zimodem): Uses Top Pin 2 (+5 V) and Top Pin 1 (GND) for power, Bottom Pin M (PA2) for TX, Bottom Pin B (/FLAG2 + PB0 Pin C bridged) for RX, and PB1–PB7 for RTS/CTS/DTR/DCD handshaking.