The IMP16C554 is a universal asynchronous receiver and transmitter with 16 byte transmit and receive FIFO. A programmable baud rate generator is provided to select transmit and receive clock rates from 50Hz to 1.5MHz. The IMP16C554 is an improved version of the IMP16C550 UART with higher operating speed and lower access time. The IMP16C554 on board status registers provides the error conditions, type and status of the transfer operation being performed. Included is complete MODEM control capability, and a processor interrupt system that may be software tailored to the user's requirements. The IMP16C554 provides internal loop-back capability for on board diagnostic testing.