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.
Supported Systems / Found On — Retro Machine Hubs
This connector is used on the following retro computer systems. Click any colour-coded badge below to open its full board-level repair, diagnostic, and schematic Machine Hub:
Connector Specifications
Top Row (6 Pins)
Pins 1, 3, 5, 7, 9, 11 (Left-to-Right looking at rear of Atari)
Bottom Row (7 Pins)
Pins 2, 4, 6, 8, 10, 12, 13 (Left-to-Right looking at rear of Atari)
Standard / Hi-Speed
19,200 baud stock (3x–6x UltraSpeed up to 68,000–125,000 baud with POKEY divisors!)
Minimum 5 Wires
Pin 3 (Data In), Pin 4 (GND), Pin 5 (Data Out), Pin 7 (/COMMAND), Pin 10 (+5V)
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| 1 (Top-Left) | CLOCK IN | In | Synchronous Serial Clock Input to POKEY Pin 26 (BCLK) | NC on SDrive/FujiNet |
| 2 (Bot-Left) | CLOCK OUT | Out | Synchronous Serial Clock Output from POKEY Pin 27 (OCLK) | NC on SDrive/FujiNet |
| 3 (Top-2nd) | DATA IN (to Atari) | In | Serial Data Input TO Atari POKEY Pin 24 (SID) — Connect to Drive TX! | Green / Orange (Drive TX -> Atari RX) |
| 4 (Bot-2nd) | GND (0 V) | GND | Primary Digital Ground Return | Black (GND) |
| 5 (Top-3rd) | DATA OUT (from Atari) | Out | Serial Data Output FROM Atari POKEY Pin 28 (SOD) — Connect to Drive RX! | Yellow / White (Atari TX -> Drive RX) |
| 6 (Bot-3rd) | GND (0 V) | GND | Secondary Ground Return | Black (GND) |
| 7 (Top-4th) | /COMMAND | Out | Active-Low Command Frame Strobe from 6520 PIA Pin 19 (CB2)! | Purple / Blue (/COMMAND) |
| 8 (Bot-4th) | CASSETTE MOTOR | Out | 410/1010 Cassette Motor Control (from PIA CA2) | NC on Disk/SDrive |
| 9 (Top-5th) | /PROCEED | In | Handshake / Proceed interrupt to PIA CA1 (used by FujiNet!) | Grey |
| 10 (Bot-5th) | +5.0V DC / READY | Pwr | +5.0 V DC Output (50 mA–300 mA — powers FujiNet & SDrive-MAX!) | Red (+5V DC) |
| 11 (Top-Right) | AUDIO IN | In | External Analog Audio Mix Input (mixed straight into TV audio!) | White (Cassette/FujiNet Audio) |
| 12 (Bot-6th) | +12V DC (400/800) | Pwr | +12 V DC Output (Present on Atari 400/800 ONLY — NC on XL/XE!) | NC |
| 13 (Bot-Right) | /INTERRUPT | In | Interrupt line to PIA CB1 | Brown |
Wiring an SDrive-MAX / Arduino Uno & Isolating Dead SIO Ports
Designed in 1978 by Joe Decuir (who later co-architected USB!), the 13-pin Atari Serial Input/Output (SIO) bus is an intelligent packet-switched serial bus driven by the POKEY UART (SID Pin 24 & SOD Pin 28) and the 6520 PIA (CB2 /COMMAND on Pin 7). Because Pin 10 provides +5 V DC directly from the computer, modern **FujiNet** Wi-Fi/SD adapters and **SDrive-MAX** touch-screen emulators plug straight in with no external power supply needed!
- 5-Wire SDrive-MAX / SIO2PC Connection: Wire Atari SIO Pin 3 (Data In) to Arduino TX (D1 via 1N4148 diode, cathode to Arduino TX!), SIO Pin 5 (Data Out) to Arduino RX (D0), SIO Pin 7 (/COMMAND) to Arduino A5, SIO Pin 10 (+5V) to 5V, and SIO Pin 4/6 (GND) to GND.
- SIO Drives Completely Ignored on Boot: Check 6520 PIA Pin 19 (CB2 -> SIO Pin 7 /COMMAND) and POKEY Pins 24 (SID) & 28 (SOD) — and inspect the small glass ESD protection diodes near the SIO jack that occasionally short to ground!