NEC uPD765 FDC

1979

NEC's floppy disk controller, the chip behind the IBM PC's diskette interface and many other 1980s computers.

Machines

Emulator	Type	License	Site
Anex86	downloadable	Freeware
CP/M Box	online	Freeware
Joyce	downloadable	GPL-2.0
M88	downloadable	Freeware
NP2kai	both	BSD-3-Clause	Website ↗
Neko Project 21/W	downloadable	BSD-3-Clause
Neko Project II	downloadable	BSD-3-Clause
QUASI88	downloadable	BSD-3-Clause
T98-Next	downloadable	Freeware
XM8	downloadable	Freeware

External technical references for programming NEC uPD765 FDC and for writing emulators.

Resource	Type	Notes
NEC µPD765A/765B Floppy Disc Controller Datasheet (HTML) ↗	Datasheet	Full NEC datasheet: all 16 commands, phases, status registers
NEC uPD765 Data Sheet (Dec 1978, bitsavers scan) ↗	Datasheet	Original NEC scan: electrical, timing diagrams, commands
NEC uPD765 Application Note (Mar 1979, bitsavers) ↗	Datasheet	NEC app note: interface circuits, PLL, write precomp
NEC µPD765A/765B Floppy Disc Controller Datasheet (HTML) ↗	Instruction set	Byte-level command/parameter/result encoding for all commands
NEC µPD765A/765B Floppy Disc Controller Datasheet (HTML) ↗	Pinout	40-pin DIP configuration and signal descriptions
NEC uPD765 Data Sheet (Dec 1978, bitsavers scan) ↗	Pinout	Original pin configuration and AC timing parameters
Programming the NEC µPD765 and Intel 82072/7 FDC ↗	Programming	Registers, DMA/IRQ6, 13+4 commands with assembly examples
µPD765A Disc Controller Primer - Muckypaws ↗	Programming	Z80 hands-on: recalibrate, seek, read/write, format
765 FDC - CPCWiki ↗	Reference	Community reference documenting quirks and undocumented behavior
Programming Floppy Disk Controllers - Ardent Tool ↗	Reference	DOR/MSR/status registers and full command set breakdown
HelpPC: NEC µPD765 / 8272A Floppy Controller ↗	Reference	Quick reference: registers, ports 3F0h-3F7h, 15 commands
floooh/chips - upd765.h emulator ↗	Source	Clean C header FDC emulation: phases, FIFO, callbacks