DESCRIPTION
The Philips Semiconductors SCC68681 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. It is manufactured in a CMOS process.

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 115.2 kbaud
    – Non-standard rates to 115.2 kb
    – Non-standard user-defined rate derived from programmable counter/timer
    – External 1× or 16× 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
    – 100 kΩ typical pull-up resistors
• Multi-function 8-bit output port
    – Individual bit set/reset capability
    – Outputs can be programmed to be status/interrupt/DMA signals
    – Auto 485 turn-around
• 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: 1× = 1 MB/sec; 16× = 125 kB/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 +5 V power supply
• Commercial and industrial temperature ranges available
• DIP and PLCC packages