Digital Design and Computer Architecture, 2nd Edition

Figure 8.39 Clock and data timing controlled by CKE, CKP, and SAMPLE

Universal Asynchronous Receiver Transmitter (UART)

A UART (pronounced “you-art”) is a serial I/O peripheral that communicates between two systems without sending a clock. Instead, the systems must agree in advance about what data rate to use and must each locally generate its own clock. Although these system clocks may have a small frequency error and an unknown phase relationship, the UART manages reliable asynchronous communication. UARTs are used in protocols such as RS-232 and RS-485. For example, computer serial ports use the RS-232C standard, introduced in 1969 by ...