The document describes the features and characteristics of the MK68564 January 1989 serial input output device. It is compatible with the MK68000 CPU and MK68000 series DMA. The device has two independent full-duplex channels and two independent baud-rate generators. It supports data rates in synchronous or asynchronous modes, with self-test capability and modem status monitoring. It also supports asynchronous, byte synchronous, and bit synchronous features, such as various data bit lengths, stop bit lengths, parity options, sync character insertion, etc.