4.6 Universal asynchronous receivers-transmitters

Universal asynchronous receiver-transmitters (UARTs) are hardware devices that allow a computer to asynchronously and serially communicate with peripheral devices. A UART uses local logic levels, usually CMOS, whereas peripheral devices sometimes use other signal levels, such as those corresponding to RS-232. In those cases, a level converter lies between a UART and a peripheral device. Often, a UART is also present in the peripheral device for reconstruction of the parallel data. A typical UART is capable of full duplex communication.

A UART can be purchased as an IC, but it typically comes integrated with most real-time single-board computers, microcontrollers, and systems on a chip (SoCs). The general operation of digital circuits will be addressed in Chapter 6, but the high-level operation of a UART is explained in 4y,47.

4.6.1 Shift registers

Shift registers

The key elements of a UART …