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
ACSI DMA Port
19-Pin D-Sub Female (DB19F) on rear of ST (Pins 1–8 = D0–D7, Pin 9 = /CS, Pin 10 = /IRQ, Pin 19 = /ACK)
Modern ACSI Drives
UltraSatan (Dual SD), ACSI2STM (STM32 SD), SatanDisk, and ICD/BlueSCSI
External Floppy Port
14-Pin Circular DIN Female (Carries Shugart signals for Drive B / DS1)
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| ACSI Pins 1–8 | D0 – D7 (8-Bit DMA) | I/O | Bidirectional 8-Bit ACSI Data Bus (Pin 1 = D0 LSB .. Pin 8 = D7 MSB) | DB19 Pins 1–8 |
| ACSI Pin 9 | /CS (Chip Select) | Out | Active-Low Command/Data Strobe | DB19 Pin 9 |
| ACSI Pin 10 | /IRQ | In | Active-Low Interrupt Request (to 68901 MFP Pin 23) | DB19 Pin 10 |
| ACSI Pin 11 | A1 (Command/Byte) | Out | Address line A1 (Low = Start of new command packet; High = Next byte) | DB19 Pin 11 |
| ACSI Pin 12 | /RESET | Out | System Reset output | DB19 Pin 12 |
| ACSI Pins 13–17 | GND (0 V) | GND | Common Ground Return (Pins 13, 14, 15, 16, 17) | DB19 Pins 13–17 (GND) |
| ACSI Pin 18 & 19 | R/W (18) & /DRQ-/ACK (19) | I/O | Pin 18 = Read/Write (1=Read, 0=Write) | Pin 19 = DMA Request/Ack | DB19 Pins 18 & 19 |
| Floppy DIN 1–14 | 14-PIN EXT FLOPPY | I/O | 1=/RD, 2=SIDE0, 3&7=GND, 4=/IP, 5=/DS0(B:), 6=/DS1, 8=/MON, 9=/DIR, 10=/STEP, 11=/WD, 12=/WG, 13=/TR00, 14=/WPRT | Shugart 34-Pin Ribbon |
Wiring an External Gotek as Drive B (14-Pin DIN to 34-Pin Ribbon)
To provide low-cost hard disk expansion on the 520ST and 1040ST, Atari created the 19-pin D-Sub ACSI (Atari Computer System Interface) port — a streamlined 8-bit DMA bus closely related to SCSI-1 capable of 1.3 MB/sec transfers. Next to it sits a proprietary 14-pin circular DIN socket for connecting an external SF354 / SF314 floppy drive (or Gotek) as Drive B.
- To connect a Gotek externally to the Atari ST's 14-pin DIN as Drive B (B:): wire DIN Pin 1 -> Ribbon 30 (/RDATA), Pin 2 -> Ribbon 32 (/SIDE), Pins 3 & 7 -> Odd Ribbon Grounds, Pin 4 -> Ribbon 8 (/INDEX), Pin 5 (/DS0 on DIN = ST Drive B!) -> Ribbon 10 (/DS0, with Gotek jumper on S0), Pin 8 -> Ribbon 16 (/MOTOR), Pin 9 -> Ribbon 18 (/DIR), Pin 10 -> Ribbon 20 (/STEP), Pin 11 -> Ribbon 22 (/WDATA), Pin 12 -> Ribbon 24 (/WGATE), Pin 13 -> Ribbon 26 (/TRK00), and Pin 14 -> Ribbon 28 (/WPT).