34 PIN MALE EDGE at the computer
The Amstrad CPC6128 Disk Drive 2 socket provides an external floppy drive interface driven by the NEC µPD765-compatible FDC9216BT controller, which supports a maximum of two drives. On UK and Danish models the connector is a 34-way 0.1-inch (2.54 mm) PCB edge connector; German and Schneider models instead use a 34-way Centronics socket. The interface carries the standard Shugart-derived floppy signals — index, drive select, motor on, direction, step, write data, write gate, track 0, write protect, read data, and side select — though the CPC6128 pin numbering is exactly reversed from the Shugart standard (Shugart pin 1 corresponds to CPC pin 34), which must be accounted for when making or adapting cables. The interface was introduced in 1985 and is designed for 3-inch or compatible double-density drives.
| Pin | Name |
|---|---|
| 1 | READY |
| 2 | GND |
| 3 | SIDE 1 SELECT |
| 4 | GND |
| 5 | READ DATA |
| 6 | GND |
| 7 | WRITE PROTECT |
| 8 | GND |
| 9 | TRACK 0 |
| 10 | GND |
| 11 | WRITE GATE |
| 12 | GND |
| 13 | WRITE DATA |
| 14 | GND |
| 15 | STEP |
| 16 | GND |
| 17 | DIRECTION SELECT |
| 18 | GND |
| 19 | MOTOR ON |
| 20 | GND |
| 21 | n/c |
| 22 | GND |
| 23 | DRIVE SELECT 1 |
| 24 | GND |
| 25 | n/c |
| 26 | GND |
| 27 | INDEX |
| 28 | GND |
| 29 | n/c |
| 30 | GND |
| 31 | n/c |
| 32 | GND |
| 33 | n/c |
| 34 | GND |
Notes
- The CPC6128 pin numbering is the exact reverse of the Shugart 34-pin standard: Shugart pin 1 = CPC pin 34, and so on. Standard off-the-shelf Shugart cables cannot be used without re-pinning or a reversal adapter.
- UK and Danish CPC6128 models use a 34-way 0.1-inch PCB edge connector; German and Schneider models use a 34-way Centronics socket. Both carry identical signals.
- Original Amstrad/Schneider cables used a blue wire to mark pin 1, which aids correct orientation.
- All even-numbered pins are ground; signal lines appear exclusively on odd-numbered pins.
- Drive Select 1 appears at pin 23 (Amstrad numbering). The Shugart equivalent would be at pin 12, which maps to CPC pin 23 in the reversed scheme.
- The system supports a maximum of two drives (internal drive 0 and external drive 1). Unused signal pins (21, 25, 29, 31, 33) are not connected.
- The internal drive is a Hitachi/Panasonic 3-inch format unit with a 12 ms step rate and 30 ms settling time.
Signals
- READY — indicates that the drive motor is running and the disk is up to speed and ready for access.
- SIDE 1 SELECT — selects the upper (side 1) read/write head on a double-sided drive; deasserted selects side 0.
- READ DATA — serial MFM-encoded data stream from the drive to the FDC during a read operation.
- WRITE PROTECT — asserted by the drive when the inserted disk is write-protected; prevents write operations.
- TRACK 0 — asserted by the drive when the read/write head is positioned over track 0 (the outermost track).
- WRITE GATE — enables the write circuitry in the drive; must be asserted before WRITE DATA is valid.
- WRITE DATA — serial MFM-encoded data stream from the FDC to the drive during a write operation.
- STEP — each pulse moves the head one track in the direction set by DIRECTION SELECT.
- DIRECTION SELECT — sets the direction of head movement; asserted steps inward (towards higher track numbers), deasserted steps outward.
- MOTOR ON — activates the drive spindle motor when asserted.
- DRIVE SELECT 1 — selects drive 1 (the external drive connected to this socket) for subsequent operations.
- INDEX — once-per-revolution pulse generated by the drive to indicate the beginning of a track; used by the FDC for timing.
- GND — signal ground; all even-numbered pins are ground returns.
- n/c — not connected; these pins carry no signal on the CPC6128 implementation.