Western Digital FD1771

The FD1771, sometimes WD1771, is a floppy disk controller chip, the first in a line of floppy disk controllers produced by Western Digital.

It uses single density FM encoding introduced in the IBM 3740.

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 (DIP) format,[1][2] later models moved to a 28-pin format that further lowered implementation costs.

The FD1771 was succeeded by many derivatives that were mostly software-compatible: Many compatible chips were available from other vendors: These were used in many microcomputers including the TRS-80, Acorn Electron, BBC Master, Atari ST, Acorn Archimedes, and the SAM Coupé, as well as the +D and DISCiPLE disk interfaces for the ZX Spectrum, the Commodore 157x/1581 for the Commodore 64 and the Atari XF551 for the Atari 8-bit computers.