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MOS 6551 ACIA
1977
MOS Technology's Asynchronous Communications Interface Adapter, a serial UART used for RS-232 in Commodore and Apple peripherals.
Reference & documentation
External technical references for programming MOS 6551 ACIA and for writing emulators.
| Resource | Type | Notes |
|---|---|---|
| WDC W65C51N ACIA Datasheet ↗ | Datasheet | Modern CMOS datasheet: registers, electrical, timing. |
| MOS 6551 ACIA Datasheet ↗ | Datasheet | Original MOS Technology datasheet with full register spec. |
| 6551 ACIA Register Summary ↗ | Memory map | Bit-by-bit control/command/status register map. |
| MOS 6551 ACIA Datasheet (pinout) ↗ | Pinout | Pin assignments and package diagram. |
| Jeff Tranter: The 6551 ACIA ↗ | Programming | Assembly serial I/O echo/getchar with register defs. |
| Experimenting with the 6551 ACIA ↗ | Programming | Register init walkthrough with assembly listing. |
| Working around the W65C51 transmit bug ↗ | Reference | TDRE-stuck errata and emulation-relevant workarounds. |
| MOS Technology 6551 (Wikipedia) ↗ | Reference | Overview, specs, variants, and known hardware bug. |
| Oricutron 6551.c ACIA emulation ↗ | Source | Clean C reference implementation of the ACIA. |
| VICE aciacore.c 6551 emulation ↗ | Source | VICE ACIA core; SwiftLink/Turbo232 variants too. |