The floppy drive is considered a legacy product at this point, still in production but not recommended for new designs. The transfer speeds are relatively slow, and the data storage capacity vary low. Data transfer speeds for Floppy Disk Drives [FDD] normally are 250KBps for the 720KB disk size and 500KBps for the 1.44MB disk size. However 1.25MBps may also be found on some drives. FDD spin at a nominal rate of 300 RPM. Common power dissipation over the 5 volt line will be in the range of 1.25 watts. Bit Density for the two common size Floppy Disks are 8717 bpi [Bits per Inch] for the 720KB size and 17434 bpi for the 1.44MB size. Two common size devices are produced for the 3.5 inch floppy drive; the standard version 25.4 x 101.6 x 146mm [H x W x D], and a reduced size version 12.7 x 96 x 126mm [H x W x D]. There are still a number of companies that Manufacturer Floppy Disk Drives. The internal case drives use the pinout described on this page, while external drives normally use a USB interface.
The table below provides the Personal Computer Drive A Pinout for either the 3 1/2 or 5 1/4 floppy drive. The cable uses a 34-pin IDC connector [requiring a 34-pin device header], and a 34-pin flat ribbon cable [IDC Definition]. The connector size differ between the two drive types, with the 5.25" drives requiring a larger connector. The 3.5" floppy drive format is the size in common use, and the common cable in general use will not have the 5.25" drive connectors. A common cable name which accepts both the 3.5" and 5.25" drives may be termed a universal cable. The pin out differences for the B drive is shown after the table. The twist in the cable causes the pin out difference, and is used to indicate which drive is the 'A' drive. External floppy drives using USB as the interface could be any size and would not use the pinout table below.
The cable connectors are female, and require male 34-pin headers on the floppy drives and Motherboard. The odd pins are on the keyed side [red cable strip] of the connector, while the other side of the connector contain the even pins. The cable length should be between 19 inches and 24 inches, while some may be as long as 32 inches [19" is standard].
| Pin No. | Signal Name | Description |
|---|---|---|
| 1 | Ground | -- |
| 2 | /REDWC | Density Select 1=Low/0=High |
| 3 | Ground | -- |
| 4 | N/C | Reserved |
| 5 | Ground | -- |
| 6 | N/C | Reserved |
| 7 | Ground | -- |
| 8 | /Index | 0=Index |
| 9 | Ground | -- |
| 10 | /MOTEA | 0=Motor Enable Drive 0 |
| 11 | Ground | -- |
| 12 | /DRVSB | Drive Select 1 |
| 13 | Ground | -- |
| 14 | /DRVSB | Drive Select 0 |
| 15 | Ground | -- |
| 16 | /MOTEB | 0=Motor Enable Drive 1 |
| 17 | Ground | -- |
| 18 | /DIR | 0=Direction Select |
| 19 | Ground | -- |
| 20 | /Step | 0=Head Step |
| 21 | Ground | -- |
| 22 | /WDATE | Write Data |
| 23 | Ground | -- |
| 24 | /WGATE | Floppy Write Enable, 0=Write Gate |
| 25 | Ground | -- |
| 26 | /TRK00 | 0=Track 00 |
| 27 | Ground | -- |
| 28 | /WPT | 0=Write Protect |
| 29 | Ground | -- |
| 30 | /RDATA | Read Data |
| 31 | Ground | -- |
| 32 | /SIDE1 | 0=Head Select |
| 33 | Ground | -- |
| 34 | /DSKCHG | 1=Disk Change/0=Ready |
The Floppy cable twist is used to determine which drive [in a multi-drive] system is drive 'A' or 'B' [also called drive '1' or '2']. From the pin out table below; the swapped pins determine the floppy drive enabled, and which motor is enabled. The pins are line 10, line 12, line 14, and line 16, while the other lines in the twist are ground lines. In general, the Floppy drive ships with a jumper positioned so that the drive is a 'B' drive, the cable does the rest. There may be other variations [dual twist] in the cable, this page explores one "common" implementation.
| -- | Controller | Drive A | Drive B | Description |
|---|---|---|---|---|
| Wire 1-9 | 1-9 | 1-9 | 1-9 | No Change |
| Wire 10 | 10 | 16 | 10 | Motor Enable Drive 0/1 |
| Wire 11 | 11 | 15 | 11 | Ground, No Change |
| Wire 12 | 12 | 14 | 12 | Drive Select 0/1 |
| Wire 13 | 13 | 13 | 13 | Ground, No Change |
| Wire 14 | 14 | 12 | 14 | Drive Select 0/1 |
| Wire 15 | 15 | 11 | 15 | Ground, No Change |
| Wire 16 | 16 | 10 | 16 | Motor Enable Drive 0/1 |
| Wire 17-34 | 17-34 | 17-34 | 17-34 | No Change |
With the introduction of inexpensive USB Flash drives, many new
Personal Computers have been shipping without a
floppy drive. PCs are now able to boot from CD or other devices. As of
the end of 2005 there are still several manufacturers producing FDD in
the 3.5" format. Floppy Drives in the 5.25 format have not shipped with
computers as long as I can remember. Floppy drives are almost obsolete
[replaced by USB flash drives] and should not be used in new designs. How
ever, my latest computer shipped with a floppy drive [to my amazement], I
assume because some drivers were only available on floppy disk. In any
case the floppy interface used 5v TTL as the electrical
interface.
IDC: Insulation Displacement Connector. A listing of connector
manufacturers may be found on the connector manufacturers page. New
'high-end' cables may be rounded cables as opposed to flat cables, but
the pinouts and connectors remain the same. The newer rounded cables are
really just a flat cable that has been formed into a circle. Additional
computer bus descriptions and pinout tables may be found by selecting the
Buses icon below. Many of the pages also include links to manufacturers
which produce the interface IC's, cables, and connectors.
The Power connector for the floppy dive is listed on the Motherboard ATX pinout page.
Design Key words: Floppy Drive, FDD, Disk, Pin Out, Standard, Personal Computer, Bus, PC, Pinouts, Pin Out, Pinout, pins Connector, Signal Names, 2row, Computer Bus, Specification, Spec, IBM Compatible Personal Computer Interface, IC, Physical Interface, Description, Boot Device, Format, peripherals, Header, IDC.
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