The 26-pin FPC (Flexible Printed Circuit) connector is a slimline variant of the standard 34-pin floppy interface, used in laptop and slim-bay 3.5-inch floppy drives such as the Panasonic JU-256A and JU-257A series. Unlike the full-size 34-pin IDC header, this connector integrates +5 V power supply lines alongside all the standard floppy control and data signals, eliminating the need for a separate power connector. The logical signal set mirrors the conventional PC floppy bus — Index, Drive Select, Motor Enable, Direction, Step, Write Data, Write Gate, Track 00, Write Protect, Read Data, Side Select, Disk Change, and Density Select — and uses the same active-LOW open-collector TTL signalling. Connector pitch varies by manufacturer: some models use a 1.25 mm pitch (e.g. AMP P/N 170204-2) whilst others use 1.0 mm (e.g. Sumitomo SMCD-26X-P1.0).
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | VCC +5V |
| 2 | /INDEX | Index |
| 3 | VCC | VCC +5V |
| 4 | /DRVS | Drive Sel |
| 5 | VCC | VCC +5V |
| 6 | /DSKCHG | Disk Change |
| 7 | RES | Reserved |
| 8 | READY | |
| 9 | MEDIA | |
| 10 | /MOTE | Motor Enable |
| 11 | /REDWC | Density Select |
| 12 | /DIR | Direction |
| 13 | RES | Reserved (Inuse) |
| 14 | /STEP | Step |
| 15 | GND | Ground |
| 16 | /WDATE | Write Data |
| 17 | GND | Ground |
| 18 | /WGATE | Write Gate |
| 19 | GND | Ground |
| 20 | /TRK00 | Track00 |
| 21 | GND | Ground |
| 22 | /WPT | Write Protect |
| 23 | GND | Ground |
| 24 | /RDATA | Read Data |
| 25 | GND | Ground |
| 26 | /SIDE1 | Side 1 Select |
Signals
- VCC — +5 V DC power supply; distributed across pins 1, 3, and 5 to share current load across the narrow FPC conductors.
- /INDEX — Active-LOW pulse output from drive to controller, generated once per spindle revolution to indicate track start.
- /DRVS — Active-LOW Drive Select input; controller asserts this line to activate the drive. Slimline drives typically support only one drive select line unlike the four available on the 50-pin SA800 interface.
- /DSKCHG — Active-LOW Disk Change output; asserted by the drive after media removal to signal the controller that the disc has been ejected or changed.
- RES — Reserved; not connected in standard implementations. Pin 13 is sometimes labelled In Use on certain drive variants.
- READY — Drive Ready output; indicates the spindle motor has reached operating speed and the drive is ready for read/write operations.
- MEDIA — Media sense output; indicates the type or density of the inserted disc on drives that support media detection.
- /MOTE — Active-LOW Motor Enable input; controller asserts this to spin up the drive’s DC spindle motor.
- /REDWC — Active-LOW Density Select (also known as High-Density Select); controller asserts to select high-density (1.44 MB) mode; deasserted for double-density (720 KB) mode.
- /DIR — Active-LOW Direction Select input; determines the direction of head movement (towards centre or track 0) when a Step pulse is received.
- /STEP — Active-LOW Step pulse input; each falling edge moves the read/write head one track in the direction set by /DIR.
- /WDATE — Active-LOW Write Data input; serial data stream from controller to drive during write operations.
- /WGATE — Active-LOW Write Gate input; controller asserts this to enable the write circuitry; must be asserted before /WDATE is valid.
- GND — Signal ground return; pins 15, 17, 19, 21, 23, and 25 are ground, providing adequate return paths for signals in the upper half of the connector.
- /TRK00 — Active-LOW Track 00 output; asserted by the drive when the read/write head is positioned at the outermost track (track 0).
- /WPT — Active-LOW Write Protect output; asserted when the inserted disc has the write-protect tab in the protected position.
- /RDATA — Active-LOW Read Data output; serial data stream from drive to controller during read operations.
- /SIDE1 — Active-LOW Side 1 Select input; controller asserts to select the upper (side 1) head; deasserted selects the lower (side 0) head.
Notes
- All signal lines use active-LOW open-collector TTL logic, consistent with the standard 34-pin PC floppy bus: TRUE (asserted) = 0.0–0.4 V; FALSE (deasserted) = +2.5–+5.25 V.
- The connector pitch varies by drive model: 1.25 mm (AMP P/N 170204-2) and 1.0 mm (Sumitomo SMCD-26X-P1.0) variants exist; verify the pitch before ordering a replacement FPC cable.
- Power (+5 V) is supplied via the same 26-pin FPC connector, distinguishing it from full-size 3.5-inch drives which use a separate 4-pin Molex power connector.
- The logical signal set is functionally equivalent to the standard 34-pin floppy interface; the reduction from 34 to 26 pins is achieved by consolidating ground returns and eliminating the unused +12 V rail (slim drives use DC motors operating on +5 V only).
- Termination resistors (150 Ω pull-up to +5 V) are required on input lines at the drive end; in a single-drive slimline configuration the drive itself provides termination internally.
References
- PS/2 Floppy Drive Interface Pinouts — citing IBM PS/2 3.5-inch Diskette Drives Technical Reference S42G-2194-00, 2nd Ed., Oct 1992