GENERAL DESCRIPTION
The EXAR Dual Universal Asynchronous Receiver and Transmitter (DUART) is a data communications device that provides two fully independent full duplex asynchronous communication channels in a single package. The DUART is designed for use in microprocessor based systems and may be used in a polled or interrupt driven environment.
The XR88C681 device offers a single IC solution for the 8080/85, 8086/88, Z80, Z8000, 68xx and 65xx microprocessor families.

FEATURES
● Two Full Duplex, Independent Channels
● Asynchronous Receiver and Transmitter
● Quadruple-Buffered Receivers and Dual Buffered Transmitters
● Programmable Stop Bits in 1/16 Bit Increments
● Internal Bit Rate Generators with More than 23 Bit Rates
● Independent Bit Rate Selection for Each Transmitter and Receiver
● External Clock Capability
● Maximum Bit Rate: 1X Clock - 1Mb/s, 16X Clock - 125kb/s
● Normal, AUTOECHO, Local LOOPBACK and Remote LOOPBACK Modes
● Multi-function 16 Bit Counter/Timer
● Interrupt Output with Eight Maskable Interrupt Conditions
● Interrupt Vector Output on Acknowledge (40 Pin DIP and 44 Pin PLCC Packages Only)
● Programmable Interrupt Daisy Chain
● 8 General Purpose Outputs (40 Pin DIP and 44 Pin PLCC Packages Only)
● 7 General Purpose Inputs with Change of States Detectors on Inputs (40 Pin DIP and 44 Pin PLCC Packages Only)
● Multi-Drop Mode Compatible with 8051 Nine Bit Mode
● On-Chip Oscillator for Crystal
● Standby Mode to Reduce Operating Power
● Compatible with the Motorola MC2681 and Signetics SCC2692 devices
● Advanced CMOS Low Power Technology

APPLICATIONS
● Multimedia Systems
● Serial to Parallel/Parallel to Serial Converter
● DTE for Modem Communication Systems