The FD1771, sometimes WD1771, is the first in a line of

floppy disk controller A floppy-disk controller (FDC) has evolved from a discrete set of components on one or more circuit boards to a special-purpose integrated circuit (IC or "chip") or a component thereof. An FDC directs and controls reading from and writing to ...

s produced by

Western Digital Western Digital Corporation (WDC, commonly known as Western Digital or WD) is an American computer drive manufacturer and data storage company, headquartered in San Jose, California. It designs, manufactures and sells data technology products ...

. It uses single density

FM encoding Frequency modulation encoding, or simply FM, is a method of storing data that saw widespread use in early floppy disk drives and hard disk drives. The data is modified using differential Manchester encoding when written to allow clock recove ...

introduced in the

IBM 3740 IBM 3740 Data Entry System was a data entry system that was announced by IBM in 1973. It recorded data on an 8" diskette, a new recording medium from IBM, for fast, flexible, efficient data entry to either high-production, centralized operations ...

. It is packaged in a 40-pin DIP."The FD1771 is a single-chip floppy disk formatter/controller that interfaces with most available disk drives and virtually all types of computers." The FD1771 was announced on July 19, 1976, and sold for $60 each in lots of 100. Later models in the series added support for MFM encoding and increasingly added onboard circuitry that formerly had to be implemented in external components. Originally packaged as 40-pin

dual in-line package In microelectronics, a dual in-line package (DIP or DIL), is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board ( ...

(DIP) format, later models moved to a 28-pin format that further lowered implementation costs.

Derivatives

The FD1771 was succeeded by many derivatives that were mostly software-compatible: *The FD1781 was designed for

double density Disk density is a capacity designation on magnetic storage, usually floppy disks. Each designation describes a set of characteristics that can affect the areal density of a disk or the efficiency of the encoded data. Such characteristics includ ...

, but required external modulation and demodulation circuitry, so it could support MFM, M2FM,

GCR GCR (or GCRS) may refer to: Science * Galactic cosmic ray, a cosmic ray from outside the Solar System * Geocentric Celestial Reference System, a coordinate system for near-Earth objects like satellites * Geological Conservation Review, a proc ...

or other double-density encodings. The FD1781 was announced on September 21, 1977. Supported Dual density; accommodates MFM, M2FM. *The FD1791-FD1797 series added internal support for

( MFM) modulation, compatible with the IBM System/34 disk format. They required an external data separator.FD 179X-02 datasheet
/ref> *The WD1761-WD1767 series were versions of the FD179x series rated for a maximum clock frequency of 1 MHz, resulting in a data rate limit of 125

kbit/s In telecommunications, data-transfer rate is the average number of bits ( bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mul ...

for single density and 250 kbit/s for double density, thus preventing them from being used for 8-in (200 mm) floppy drives or the later "high-density" or 90 mm floppy drives. These were sold at a lower price point and widely used in home computer floppy drives. *The WD2791-WD2797 series added an internal data separator using an analog

phase-locked loop A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a ...

, with some external passive components required for the VCO. They took a 1 MHz or 2 MHz clock and were intended for and drives. *The WD1770, WD1772, and WD1773 added an internal digital data separator and write precompensator, eliminating the need for external passive components but raising the clock rate requirement to 8 MHz. They supported double density, despite the apparent regression of the part number, and were packaged in 28-pin DIP packages.WD177X-00 datasheet images
/ref> *The WD1772PH02-02 was a version of the chip that Atari fitted to the

Atari STE The Atari ST is a line of personal computers from Atari Corporation and the successor to the Atari 8-bit family. The initial model, the Atari 520ST, had limited release in April–June 1985 and was widely available in July. It was the first pe ...

which supported high density (500 kbit/s) operation. After production at WD could not be sustained, Atari decided to license the design and modify it to get high density and extra density (1 MBit/s) operation. The chip was codenamed "Ajax", had the number C302096 and was produced by Toshiba.

Compatible chips

Many compatible chips were available from other vendors: *FD179x series from SMC Microelectronics *MB8876A and MB8877A from

Fujitsu is a Japanese multinational information and communications technology equipment and services corporation, established in 1935 and headquartered in Tokyo. Fujitsu is the world's sixth-largest IT services provider by annual revenue, and the la ...

*VL177x series from VLSI Technology. *Soviet KR1818WG93 (КР1818ВГ93) was a WD1793 analog These families were used in many

microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (P ...

s and home computers including the Radio Shack TRS-80,

Acorn Electron The Acorn Electron (nicknamed the Elk inside Acorn and beyond) was a lower-cost alternative to the BBC Micro educational/home computer, also developed by Acorn Computers Ltd, to provide many of the features of that more expensive machine at a p ...

BBC Master The BBC Master is a home computer released by Acorn Computers in early 1986. It was designed and built for the British Broadcasting Corporation (BBC) and was the successor to the BBC Micro Model B. The Master 128 remained in production until 199 ...

, Atari ST,

Acorn Archimedes Acorn Archimedes is a family of personal computers designed by Acorn Computers of Cambridge, England. The systems are based on Acorn's own ARM architecture processors and the proprietary operating systems Arthur and RISC OS. The first models ...

and the

SAM Coupé Sam, SAM or variants may refer to: Places * Sam, Benin * Sam, Boulkiemdé, Burkina Faso * Sam, Bourzanga, Burkina Faso * Sam, Kongoussi, Burkina Faso * Sam, Iran * Sam, Teton County, Idaho, United States, a populated place People and fictiona ...

, as well as the +D and

DISCiPLE A disciple is a follower and student of a mentor, teacher, or other figure. It can refer to: Religion * Disciple (Christianity), a student of Jesus Christ * Twelve Apostles of Jesus, sometimes called the Twelve Disciples * Seventy disciples in t ...

disk interfaces for the Sinclair ZX Spectrum, the Commodore 157x/ 1581 for the Commodore 64 and the

Atari XF551 The XF551 was the last floppy disk drive produced by Atari for the 8-bit series home computers. It was the first drive from the company that officially supported double-density, adding double-sided support, providing 360 kB of storage per ...

for the Atari XL/XE.

Derivatives

Compatible chips

References

Further reading