7 pin female EDGE connector at the computer.
The Spectravideo SVI-318 and SVI-328 (both MKI and MKII variants) are pre-MSX home computers introduced in 1983 that use a proprietary 7-pin female edge connector for cassette tape storage. The interface carries analogue audio data signals (CASR for read, CASW for write), a motor enable line, and a 12 V supply for the cassette deck’s motor relay. This connector is entirely distinct from the MSX standard DIN 45326 8-pin socket adopted on the later Spectravideo SVI-728 and all other MSX-compliant machines; the two must not be confused or interchanged. Cassette signals are routed through the AY-3-8910 PSG chip’s I/O lines alongside dedicated cassette interface circuitry, as documented in the official SVI-3x8 Service & Technical Manual.
| Pin | Name | Description |
|---|---|---|
| 1 | 12v | Power 100mA |
| 2 | CASR | Cassette data read |
| 3 | CASW | Cassette data write |
| 4 | AUDIO | Cassette audio |
| 5 | GND | System ground |
| 6 | ME | |
| 7 | READY | System Ready |
Signals
- 12v — 12 V supply (100 mA maximum) provided to the cassette unit, used to power the motor relay mechanism.
- CASR — Cassette data read; analogue audio signal from the cassette deck’s playback (EAR) output into the computer.
- CASW — Cassette data write; analogue audio signal from the computer to the cassette deck’s record (MIC) input.
- AUDIO — Cassette audio monitor output.
- GND — System ground reference.
- ME — Motor Enable; controls the cassette deck’s transport motor, allowing the computer to start and stop tape movement under software control. Referenced in the SVI-3x8 service manual diagnostics as the motor enable signal.
- READY — System Ready signal.
Notes
- This is a pre-MSX proprietary interface. The SVI-318 and SVI-328 are not MSX-compatible computers; the later SVI-728 is MSX-compliant and uses the entirely different MSX DIN 45326 8-pin cassette connector.
- The edge connector pitch and pinout are specific to Spectravideo’s own SVI-903 and SVI-904 data cassette units, as referenced in SVI-3x8 service documentation.
- The AY-3-8910 PSG chip is involved in cassette I/O alongside dedicated cassette interface lines on these machines.
- Signal encoding follows FSK (Frequency Shift Keying) conventions consistent with the era’s home computer cassette interfaces.
References
- Service & Technical Manual SVI-3x8 (GB) — SVI-318/328 MKI/MKII — Spectravideo, 1984
- MSX SVI-728 Service and Technical Manual Vol. 1 — Spectravideo, 1985 (MSX-compliant successor, confirms connector distinction)