MOS Technology 6522

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The MOS Technology 6522 Versatile Interface Adapter (VIA) is an integrated circuit that was designed and manufactured by MOS Technology as an I/O port controller for the 6502 family of microprocessors. It provides two bidirectional 8-bit parallel I/O ports, two 16-bit timers (one of which can also operate as an event counter), and an 8-bit shift register for serial communications or data conversion between serial and parallel forms. The direction of each bit of the two I/O ports can be individually programmed. In addition to being manufactured by MOS Technology, the 6522 was second sourced by other companies including Rockwell and Synertek.

The 6522 was widely used in computers of the 1980s, particularly Commodore's machines,^[1] and was also a central part of the designs of the Apple III, Oric-1 and Oric Atmos, BBC Micro, Victor 9000/Sirius 1 and Apple Macintosh. Video game platforms such as the Vectrex also used the 6522, as did the 1984 through 1989 Corvette digital dash cluster. A high speed, CMOS version, the W65C22, is produced by the Western Design Center (WDC).