GENERAL DESCRIPTION
   The XR16M554 (M554) is a quad Universal Asynchronous Receiver and Transmitter (UART) with 16 bytes of transmit and receive FIFOs, selectable receive FIFO trigger levels and data rates of up to 4 Mbps at 3.3 V. Each UART has a set of registers that provide the user with operating status and control, receiver error indications, and modem serial interface controls. An internal loopback capability allows onboard diagnostics. 

FEATURES
● Pin-to-pin compatible with ST16C454, ST16C554,
   TI’s TL16C554A and NXP’s SC16C554B
● Intel or Motorola Data Bus Interface select
● Four independent UART channels
   ■ Register Set Compatible to 16C550
   ■ Data rates of up to 4 Mbps at 3.3 V, 3.125
      Mbps at 2.5 V and 2 Mbps at 1.8 V
   ■ 16 byte Transmit FIFO
   ■ 16 byte Receive FIFO with error tags
   ■ 4 Selectable RX FIFO Trigger Levels
   ■ Full modem interface
● 1.62V to 3.63V supply operation
● Crystal oscillator or external clock input

APPLICATIONS
● Portable Appliances
● Telecommunication Network Routers
● Ethernet Network Routers
● Cellular Data Devices
● Factory Automation and Process Controls