8250 UART

1978

National Semiconductor's original PC UART, the serial-port controller in the first IBM PC and XT.

Reference & documentation

External technical references for programming 8250 UART and for writing emulators.

Resource	Type	Notes
INS8250A/8250A UART Datasheet (National Semiconductor) ↗	Datasheet	Original manufacturer datasheet: registers, timing, electrical specs
8250 Interrupt Identification Register (Wikibooks) ↗	Interrupt list	IIR priorities and interrupt sources with reset conditions
8250 UART Port and Register Reference (HelpPC) ↗	Memory map	Full I/O port map and register bit tables
8250 UART Register Table (Wikibooks) ↗	Memory map	12 registers across 8 I/O offsets
INS8250A UART Datasheet Pinout (National Semiconductor) ↗	Pinout	Full 40-pin DIP pinout and signal descriptions
Pin Diagram of 8250 UART (EEEGuide) ↗	Pinout	Annotated pin and block diagrams with descriptions
Serial Programming: 8250 UART Programming (Wikibooks) ↗	Programming	Definitive register-by-register 8250 programming guide with code
8250 UART Programming for Emulator Authors (SEBHC) ↗	Programming	Register functions plus emulator-specific behavior notes
Serial UART In-Depth Tutorial (Lammert Bies) ↗	Reference	Every register and bit documented in tables
8250 UART Technical Information (Tech Edge) ↗	Reference	Compact register and bit-definition reference
8250 UART (Wikipedia) ↗	Reference	History, variants, bugs, and interface overview
Linux Kernel 8250/16550 Port Driver Source ↗	Source	Production driver: real register handling and quirks