[FDD Description] [FDD Cable] [Floppy Disk Drive Pinout]
[FDD Cable Twist] [FDD Legacy]
The floppy drive is considered a legacy product at this point, still in
production but not recommended for new designs. Even the smallest USB Thumb Drive on the market has more memory and cost less than a floppy drive. In addition the semiconductor memory within the USB drive will not have the shock and vibration issues that the mechanical floppy drive has.
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.
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].
Connector topics; Shrouded Header Definition, and an Un-Shrouded Header Definition, and a list of Header Connector Manufacturers.
The header consists of two rows of 17 pins. The header pins are male while the cable side of the connector has female pins.
The pin-to-pin spacing is 0.1 inch, which is also a standard for many other applications.
Note some manufacturers may color code their headers to assist in troubleshooting, color-coding is not referenced in the standard.
Ribbon cable topics; note the military and much of the government uses the term flat cable and not ribbon cable to describe the style.
The ribbon cable uses stranded 28 gauge wire, with a nominal impedance of between 70 to 90 ohms. Ribbon Cable Diagram showing wire placement.
A list of Companies making Ribbon Cable, with links to other standards using flat cable.
Some newer style IDE cables may appear to be round, but it's the same flat cable in a circular jacket.
|Pin No.||Signal name||Description|
|2||/REDWC||Density Select 1=Low/0=High|
|10||/MOTEA||0=Motor Enable Drive 0|
|12||/DRVSB||Drive Select 1|
|14||/DRVSB||Drive Select 0|
|16||/MOTEB||0=Motor Enable Drive 1|
|24||/WGATE||Floppy Write Enable, 0=Write Gate|
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 a CD or other devices. As of
the end of 2010 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, the last computer that shipped with a floppy drive which I purchased was in 2005, I
assume because some software drivers were only available on floppy disk.
The pin out for a power connector for the floppy drive is listed on'
ATX Floppy Drive pinout, or Motherboard ATX pinout page.
Navigation > Engineering Home > Interface Buses > Personal Computer Buses > Floppy Drive Interface.
Related PC Interfaces > Hard Drive IDE Interface
At this point in time it should be obvious that no standard organization will be up-dating the floppy disk interface specification.
The upgrade path would be to replace the entire computer, which would include the floppy drive with the older interface.
For reference the search history or trend for the term floppy drive has been declining year after year.
Topic Navigation: Engineering Home > Interface Buses > Personal Computer Buses > IDE Hard Drive Interface.