Floppy disk drive interface

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"Shugart bus" redirects here. For the SASI see, see Shugart Associates System Interface.

Each generation of floppy disk drive (FDD) began with a variety of incompatible interfaces but soon evolved into one de facto standard interface for the generations of 8-inch FDDs, 5¼-inch FDDs and 3½-inch FDDs.[1] For example, before adopting 3½-inch FDD standards for interface, media and form factor there were drives and media proposed by Hitachi, Tabor, Sony, Tandon, Shugart and Canon.[2]

Standard 8-inch FDD interface[]

The de facto standard 8-inch FDD interface is based upon the Shugart Associates models SA800/801[3] FDDs and models SA850/851[4] FDDs.[5]: 171  The signal interface uses a dual in-line 50-pin PCB edge connector which mates to a flat ribbon cable connector; separate connectors are provided for both AC and DC power.[3][4]

Standard 5¼-inch FDD interface[]

Connectors for 5¼-inch or 3½-inch FDD (Drive "A") at end of universal two drive FDD cable. Note twist in flat cable.

The de facto standard 5¼-inch FDD interface is based upon the Shugart Associates SA400[6] FDD.[5]: 169  The signal interface uses a dual in-line 34-pin PCB edge connector which mates to a flat ribbon cable connector; a separate connector is for DC power.[6] The 34-pin connector is similar in pinout to the standard 50-pin connector for 8-inch FDDs.

IBM with its PC sliced the cable to the second drive and twisted four of the lines to eliminate the need to change selection jumpers in the drive when installing it as a second drive; the signal meaning at the drive interface pins do not change but a drive will receive a different specific selection signal depending upon its location on a cable constructed in this manner. Many manufacturers adopted this cabling but on some systems, it may be necessary to install jumpers in a drive to get proper selection.[7]

Standard 3½-inch FDD interface[]

It uses a dual in-line pin style connector mating to a socket connector, collectively slightly smaller than the PCB edge pin connecter and mating socket used for the 5¼-inch standard but with the same 34-pin definitions as the 5¼-inch standard.[8] A universal cable would have four drive connectors, two for each size of FDD.

See also[]

  • Floppy disk controller

References[]

  1. ^ Mueller, Scott (2006-03-24). "Floppy Disk Drives, Past and Present". Upgrading and Repairing PCs. flylib.com (17 ed.). Que Publishing. ISBN 0-7897-3404-4. ISBN 978-0-7897-3404-4 EAN 2147483647. Archived from the original on 2022-01-08. Retrieved 2022-01-01. […] all PC floppy disk drives are still based on (and mostly compatible with) the original Shugart designs, including the electrical and command interfaces. […] The standard interface that all PC floppy disk drives use is called the Shugart Associates SA400 interface. It was invented in the 1970s and is based on the NEC 765 controller chip.
  2. ^ Abraham, Robert (January 1983). "Microfloppy Drives Achieve High Densities and Faster Data Access". Computer Technology Review. p. 239.
  3. ^ a b SA800/801 Diskette Storage Drive (PDF). OEM Manual. Sunnyvale, California, USA: Shugart. May 1980. P/N 50574-4. Archived (PDF) from the original on 2021-03-09. Retrieved 2022-01-02. (1+iv+40+1 pages)
  4. ^ a b "SA850/851 Bi-Compliant Double Sided Diskette Storage Drive" (PDF). OEM Manual. Sunnyvale, California, USA: Shugart. November 1980. P/N 39017-0. Archived (PDF) from the original on 2020-11-29. Retrieved 2022-01-02. (1+iv+50+1 pages)
  5. ^ a b Porter, James (February 1982). "Floppy-disk drives: a truly flexible industry standard". Mini-Micro Systems. Cahners Publishing Company. pp. 169, 171. pp. 169, 171: […] SA400, Industry standard for size and interface […] SA800, SA801, SA850, SA851, Industry standard for size and interface […]
  6. ^ a b SA400L Minifloppy Diskette Storage Drive (PDF). OEM Manual. Sunnyvale, California, USA: Shugart. November 1982 [1981]. P/N 39019-1. Archived (PDF) from the original on 2020-07-27. Retrieved 2022-01-02. (2+iv+29+1 pages)
  7. ^ Farquhar, David "Dave" L. (2021-11-24). "Floppy drive pinout". The Silicon Underground. Archived from the original on 2022-01-08. Retrieved 2022-01-04. The pinouts for all these drives are all based on the original Shugart floppy drive [… of the SA800 Series], but many manufacturers changed them slightly to suit their own purposes.
  8. ^ Davis, Larry (2015-06-13). "Floppy Disk Drive Pinout". www.interbus.com. Archived from the original on 2022-01-07. Retrieved 2022-01-06.

Further reading[]

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