DESCRIPTION
The Philips Semiconductors SCN68681 Dual Universal Asynchronous Receiver/Transmitter (DUART) is a single-chip MOS-LSI communications device that provides two independent full-duplex asynchronous receiver/transmitter channels in a single package. It is compatible with other S68000 family devices, and can also interface easily with other microprocessors. The DUART can be used in polled or interrupt driven systems.

FEATURES
• S68000 bus compatible
• Dual full-duplex asynchronous receiver/transmitter
• Quadruple buffered receiver data registers
• Programmable data format
    – 5 to 8 data bits plus parity
    – Odd, even, no parity or force parity
    – 1, 1.5 or 2 stop bits programmable in 1/16-bit increments
• Programmable baud rate for each receiver and transmitter selectable from:
    – 22 fixed rates: 50 to 115.2k baud
    – Non-standard rates to 115.2kb
    – Non-standard user-defined rate derived from programmable counter/timer
    – External 1X or 16X clock
• 16-bit programmable Counter/Timer
• Parity, framing, and overrun error detection
• False start bit detection
• Line break detection and generation
• Programmable channel mode
    – Normal (full-duplex)
    – Automatic echo
    – Local loopback
    – Remote loopback
• Multi-function programmable 16-bit counter/timer
• Multi-function 6-bit input port
    – Can serve as clock or control inputs
    – Change-of-state detection on four inputs
    – 100kΩ typical pull-up resistors
• Multi-function 8-bit output port
    – Individual bit set/reset capability
    – Outputs can be programmed to be status/interrupt signals
• Versatile interrupt system
– Single interrupt output with eight maskable interrupting conditions
    – Interrupt vector output on interrupt acknowledge
    – Output port can be configured to provide a total of up to six separate wire-ORable interrupt outputs
• Maximum data transfer rates: 1X - 1MB/sec, 16X - 125kB/sec
• Automatic wake-up mode for multidrop applications
• Start-end break interrupt/status
• Detects break which originates in the middle of a character
• On-chip crystal oscillator
• Single +5V power supply
• Commercial and industrial temperature ranges available
• DIP and PLCC packages