Texas Instruments Quad-Channel UART 68-Pin PLCC, TL16C554FN

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.