The Texas Instruments TL16C452 provide single- and dual-channel (respectively) serial interfaces along with a single Centronix-type parallel-port interface. The serial interfaces provide a serial-to-parallel conversion for data received from a peripheral device or modem and a parallel-to-serial conversion for data transmitted by a CPU. The parallel interface provides a bidirectional parallel data port that fully conforms to the requirements for a Centronix-type printer interface. A CPU can read the status of the asynchronous communications element (ACE) interfaces at any point in the operation. The status includes the state of the modem signals (CTS\, DSR\, RLSD\, and RI) and any changes to these signals that have occurred since the last time they were read, the state of the transmitter and receiver including errors detected on received data, and printer status. The TL16C451 and TL16C452 provide control for modem signals (RTS\ and DTR\), interrupt enables, baud rate programming, and parallel-port control signals.

Integrates Most Communications Card Functions From the IBM PC/ATTM or Compatibles With Single- or Dual-Channel Serial Ports
TL16C451 Consists of One TL16C450 Plus Centronix Printer Interface
TL16C452 Consists of Two TL16C450s Plus a Centronix-Type Printer Interface
Fully Programmable Serial Interface Characteristics:
5-, 6-, 7-, or 8-Bit Characters
Even-, Odd-, or No-Parity Bit Generation and Detection
1-, 1 1/2-, or 2 Stop-Bit Generation
Programmable Baud Rate
(dc to 256 Kbit/s)
Fully Double Buffered for Reliable
Asynchronous Operation

A Universal Asynchronous Receiver/Transmitter, abbreviated (UART) and universal synchronous/asynchronous receiver/transmitter (USART) are commonly used in conjunction with communication standards such as EIA, RS-232, RS-422 or RS-485. It takes bytes of data and transmits or receives the individual bits in a sequential fashion. Modem (Modulator-Demodulator) that modulates an analogue carrier signal to encode digital information and demodulates the signal to decode the transmitted information includes the UART function for transmission over telephone lines.