PC/AT 3.5" Floppy Disc Drive. Computer Port (Connector)
PC/AT 3.5" Floppy Disc Drive Interface
| PC/AT 3.5" Floppy Disc Drive Interface: (1) | ||
|---|---|---|
| Direction | 34w IDC Connector | Description |
| IN | 34 | /DISKETTE CHANGE (2) |
| - | 33 | Signal Ground |
| OUT | 32 | /SIDE 1 SELECT |
| - | 31 | Signal Ground |
| IN | 30 | /READ DATA |
| - | 29 | Signal Ground |
| IN | 28 | /WRITE PROTECT |
| - | 27 | Signal Ground |
| IN | 26 | /TRACK 00 |
| - | 25 | Signal Ground |
| OUT | 24 | /WRITE GATE |
| - | 23 | Signal Ground |
| OUT | 22 | /WRITE DATA |
| - | 21 | Signal Ground |
| OUT | 20 | /STEP |
| - | 19 | Signal Ground |
| OUT | 18 | /DIRECTION SELECT |
| - | 17 | Signal Ground |
| OUT | 16 |
/MOTOR ON (/MOTOR ON B) (3) |
| - | 15 | Signal Ground |
| OUT | 14 |
/DRIVE SELECT 2 (/DRIVE SELECT A) (3) |
| - | 13 | Signal Ground |
| OUT | 12 |
/DRIVE SELECT 1 (/DRIVE SELECT B) (3) |
| - | 11 | Signal Ground |
| OUT | 10 |
/DRIVE SELECT 0 (/MOTOR ON A) (3) |
| - | 9 | Signal Ground |
| IN | 8 | /INDEX |
| - | 7 | Signal Ground |
| OUT | 6 | /DRIVE SELECT 3 |
| - | 5 | Signal Ground |
| - | 4 | RESERVED |
| - | 3 | Signal Ground |
| OUT | 2 | /REDUCED WRITE (4) |
| - | 1 | Signal Ground |
(1) Source: Peter Norton's Inside the PC, Premier Edition, National Semiconductor's application note AN-631, and FDD manufacturer's data-sheeets.
(2) Exists on low and dual-density 3.5" drives, and on dual-density 5.25" drives, but NOT low-density 5.25" drives. Inverse of the old "/READY" signal - expected to be LOW when a disk is NOT in the drive.
(3) IBM "Twisted-Cable" system - both drives strapped to use DS1.
(4) Active (low) for HIGH density on a 3.5" dual-density drive, but active (low) for LOW density on a 5.25" dual-density drive. Jumper Selectable for TEAC FD-235 drives with part numbers 19307xxx-xx see: TEAC FDD Jumpers . No connection on later models that "auto-select".