8 PIN DIN (DIN45326) FEMALE at the computer
8 PIN DIN (DIN45326) MALE at the cassette cable
The MSX cassette port is an 8-pin DIN 45326 female socket, defined in the MSX Technical Data Book (Sony/ASCII, 1984) and mandated across all MSX-compliant machines from manufacturers including Sony, Yamaha, Panasonic, and Spectravideo. It carries an FSK audio data output to the cassette recorder’s MIC input, an FSK audio data input from the recorder’s EAR output, and a relay-switched pair for remote motor control. Data encoding uses Frequency Shift Keying at either 1200 baud (1200 Hz = ‘0’, 2400 Hz = ‘1’) or 2400 baud (2400 Hz = ‘0’, 4800 Hz = ‘1’), with synchronisation managed entirely in software.
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | GND | - | Ground |
| 2 | GND | - | Ground |
| 3 | GND | - | Ground |
| 4 | CMTOUT | OUT | Sound Output |
| 5 | CMTIN | IN | Sound Input |
| 6 | REM+ | OUT | Remote control (from relay) |
| 7 | REM- | OUT | Remote control (from relay) |
| 8 | GND | - | Ground |
Signals
- GND — Four ground pins (1, 2, 3, 8) provide a common reference and shielding for the audio signals.
- CMTOUT — Cassette Motor Tape OUT; FSK audio signal from the computer to the cassette recorder’s MIC (record) input. Output level is specified at −45 dBm ± 5 dBm (where 0 dBm = 0.775 V RMS).
- CMTIN — Cassette Motor Tape IN; FSK audio signal from the cassette recorder’s EAR (playback) output to the computer. Expected input level is approximately 22–700 mVp-p at 1200 Hz.
- REM+ — Positive terminal of the relay contact used for remote motor control; connects to the cassette recorder’s remote jack to start the tape transport.
- REM- — Negative terminal of the same relay; together with REM+ forms an isolated, software-controlled relay switch — no voltage is applied to the recorder’s motor circuit directly.
Notes
- Direction is computer relative to cassette.
- The connector is a DIN 45326 (8-pin) female socket on the computer side; the cassette cable terminates in a DIN 45326 male plug.
- Motor control is implemented via an isolated relay (REMOTE+/REMOTE−), making it electrically safe to connect to any standard cassette recorder’s remote-control jack regardless of its voltage requirements.
- The MSX standard permits two baud rates: 1200 baud (default) and 2400 baud; both use FSK modulation and are controlled entirely by software with no hardware mode-switch.
- A standard consumer audio cassette deck with adequate frequency response (300 Hz–3 kHz) and low wow/flutter is sufficient; no specialised recorder hardware is required.
- The Spectravideo SVI-728 MSX machine uses this identical DIN 45326 connector and pinout, as confirmed by the SVI-728 Service and Technical Manual (Spectravideo, 1985). The earlier, non-MSX SVI-318/328 uses a different 7-pin edge connector and must not be confused with this standard.
References
- MSX Technical Data Book — ASCII / Sony, 1984
- MSX SVI-728 Service and Technical Manual Vol. 1 — Spectravideo, 1985