Interactive Connector Diagram
Click or tap any pin in the diagram below to inspect its signal assignment, electrical specification, and wire colour standard.
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
Full Pin Assignment & Wiring Reference
| Pin | Signal Name | Direction | Electrical Spec / Role | Wire Colour / SCART / Adapter Target |
|---|---|---|---|---|
| ZX Spec Pin 5A/5B | KEYWAY SLOT! | NC | MANDATORY Polarising Keyway Slot on ZX Spectrum (prevents fatal +9V offset!) | Plastic Key Tab |
| ZX Spec Pin 3B & 4B | +5V (3B) & +9V (4B) | Pwr | ZX Spectrum +5 V DC (Pin 3B) & Unregulated +9 V DC (Pin 4B; Pin 20B=+12V) | Red (+5V / +9V) |
| ZX Spec Pin 25B | /ROMCS (High=Disable) | In | Pulling Pin 25B HIGH (+5V via transistor/diode) disables internal Spectrum ROM! | DivMMC / IF1 ROM Override |
| CPC Edge Pin 43 & 45 | /ROMDIS (43) & /RAMDIS (45) | In | Amstrad CPC External ROM Disable (Pin 43) & RAM Disable (Pin 45) | M4 Board / DDI-1 |
| MSX Cart Pin 1, 2, 3 | /CS1, /CS2, /CS12 | Out | MSX Page 1 ($4000–$7FFF), Page 2 ($8000–$BFFF) & Combined $4000–$BFFF Selects | MSX 16K/32K Cart ROM |
| MSX Cart Pin 4 | /SLTSL (Slot Select) | Out | MSX Primary 64KB Slot Select (used by MegaROMs,Carnivore2 & RAM Mappers) | MSX Slot Enable |
| MSX Cart Pin 10 | /BUSDIR | In | Active-Low Bus Direction (cartridge must pull low during external I/O reads!) | MSX I/O Direction |
| MSX Cart Pins 44 & 46 | SW1 (44) & SW2 (46) | I/O | MSX Cartridge Insertion Safety Loop (shorted together on cartridge PCB!) | Bridge 44 to 46 |
| MSX Cart Pin 45, 48, 50 | +5V (45/47), +12V (48), -12V (50) | Pwr | MSX Cartridge Power Rails (+12V/-12V power SCC & FM-PAC audio amps!) | Power Rails |
| MSX Cart Pin 49 | SOUNDIN | In | MSX External Cartridge Audio Input (mixes Konami SCC / YM2413 into TV audio!) | Audio Mix In |
Cleaning ZX Spectrum & Amstrad CPC Edge Fingers for DivMMC / M4 Boards
Z80-based home computers expose the full Z80A address, data, and control bus for external ROM/RAM paging and SD-card interfaces: the ZX Spectrum uses a 2x28 (56-contact, 0.1" pitch) rear card edge with /ROMCS (Pin 25B) to override the internal BASIC ROM; the Amstrad CPC uses a 2x25 (50-contact) edge with /ROMDIS (Pin 43) and /RAMDIS (Pin 45); and MSX computers use a 50-pin top/front Cartridge Slot with /SLTSL (Pin 4) and safety insertion loop pins SW1/SW2 (Pins 44/46).
- 90% of random crashes with a ZX Spectrum DivMMC Future / Smart Card or Amstrad CPC M4 / Ulifac board are caused by 40 years of flux residue and tin/gold tarnish on the rear PCB edge fingers: rub both sides of the edge connector briskly with a soft white Staedtler Mars plastic eraser and wipe clean with 99% IPA.