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Intel 8251 USART
1976
Intel's Universal Synchronous/Asynchronous Receiver-Transmitter, a programmable serial communications chip for 8080/8085 systems.
Reference & documentation
External technical references for programming Intel 8251 USART and for writing emulators.
| Resource | Type | Notes |
|---|---|---|
| Intel 8251 USART Datasheet ↗ | Datasheet | Original Intel datasheet: full electrical, timing, registers |
| Intel 8251 Datasheet (grauw archive) ↗ | Datasheet | Clean scan of Intel 8251 datasheet |
| 8251A Datasheet (Rochester reprint) ↗ | Pinout | Pinout, signal descriptions and AC timing diagrams |
| 8251 Pin Diagram and Signal Descriptions ↗ | Pinout | Per-pin signal descriptions: Tx/Rx, modem, SYNDET |
| Programming the 8251A (NJIT EE395) ↗ | Programming | Mode/command/status words with init sequence, asm examples |
| Intel 8251 (Wikipedia) ↗ | Reference | Overview: 28-pin DIP, functional sections, variants |
| MAME i8251.cpp emulation source ↗ | Source | Reference 8251 implementation; covers uPD71051 clone |
| MAME i8251.h register/status definitions ↗ | Source | Status flag constants and device interface signals |