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PC/AT 3.5" Floppy Disc Drive. Computer Port (Connector)

PC/AT 3.5" Floppy Disc Drive Interface

34WIDC
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".

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