| Pin | Name | Description |
|---|---|---|
| 1 | AO | Audio Out |
| 2 | CVIDEO | Composite Video |
| 3 | GPO | General Purpose Output - linked to Port A bit 6 of the sound chip, user programmable |
| 4 | M detect | if line is low, ST enters high res monochrome mode (no other use) linked to pin 17 of MFP68901 chip |
| 5 | AI | Audio In |
| 6 | G | Green |
| 7 | R | Red |
| 8 | +12V | +12 VDC (520ST has GND) |
| 9 | HSYNC | Horizontal Sync |
| 10 | B | Blue |
| 11 | MVIDEO | Monochrome Video |
| 12 | VSYNC | Vertical Sync |
| 13 | GND | Ground |
