The ST16C552/ST16C552A (552/552A) is a dual universal asynchronous receiver and transmitter (UART) with an added bi-directional parallel port that is directly compatible with a CENTRONICS type printer. The parallel port is designed such that the user can configure it as general purpose I/O interface, or for connection to other printer devices. The 552/552A provides enhanced UART functions with 16 byte FIFOs, a modem control interface, and data rates up to 1.5Mbps. Onboard status registers provide the user with error indications and operational status. The system interrupts and control may be tailored to meet user requirements. An internal loop-back capability allows onboard diagnostics. A programmable baud rate generator is provided to select transmit and receive clock rates from 50 bps to 1.5 Mbps. The 552/552A is available in a 68 pin PLCC package. The 552/552A is compatible with the 16C450 and 16C550. The difference between the ST16C552 and ST16C552A is the logic state of the printer port, INTP interrupt. The INTP interrupt is active high (logic 1) on the ST16C552 whereas INTP is active low (logic 0) on the ST16C552A part when the interrupt latch mode is selected. The 552/552A is fabricated in an advanced CMOS process with power down mode to reduce the power consumption. The 552A does not support the power down mode.