MOS Technology 6551
（重定向自Asynchronous Communications Interface Adapter）
The 6551 Asynchronous Communications Interface Adapter (ACIA) was an integrated circuit made by MOS Technology. It served as a companion UART chip for the widely popular 6502 microprocessor. Intended to implement RS-232, its specifications called for a maximum speed of 19,200 bits per second. It was used in the Commodore PET, Commodore Plus/4, Apple Computer's Super Serial Card for the Apple II family, and possibly other lesser-known computers.