UART
Universal Asynchronous Receiver/Transmitter, usually called UART, is a type of asynchronous receiver/transmitter, which is part of computer hardware. It converts the data to be transmitted between serial communication and parallel communication. As a chip that converts parallel input signals into serial output signals, UART is usually integrated on the link of other communication interfaces.
The specific physical object is represented as an independent modular chip or as a peripheral device integrated in a microprocessor. Generally it is RS-232C specification, matched with a standard signal amplitude conversion chip like Maxim's MAX232, as an interface for connecting external devices. A product that adds a synchronous serial signal conversion circuit to the UART is called USART (Universal Synchronous Asynchronous Receiver Transmitter).
definition
UART is a universal serial data bus used for asynchronous communication. This bus has two-way communication and can realize full-duplex transmission and reception. In embedded design, UART is used for communication between host and auxiliary equipment, such as communication between car audio and external AP. Communication with PC includes communication with monitoring debugger and other devices, such as EEPROM.
USART
USART: (Universal Synchronous/Asynchronous Receiver/Transmitter) Universal Synchronous/Asynchronous Receiver/Transmitter USART is a full-duplex universal synchronous/asynchronous serial transceiver module. The interface is a highly flexible serial communication device.
Structure and composition
The USART transceiver module is generally divided into three parts: clock generator, data transmitter and receiver. The control register is shared by all modules.
The clock generator consists of a synchronous logic circuit (driven by an external clock input in synchronous slave mode) and a baud rate generator. The sending clock pin XCK is only used in synchronous sending mode,
The transmitter part is composed of a separate write buffer (transmit UDR), a serial shift register, a parity generator and a control logic circuit for processing different frame structures. The write buffer is used to realize the communication without delay in sending multiple frames of data continuously.
The receiver is the most complicated part of the USART module, the most important is the clock and data receiving unit. The data receiving unit is used to receive asynchronous data. In addition to the receiving unit, the receiver also includes a check bit checker, control logic, shift register and two-stage receiving buffer (receiving UDR). The receiver supports the same frame structure as the transmitter, and supports the detection of frame errors, data overflow, and check errors.
The difference between UART and USART
Both UART and USART are serial communication on the microcontroller, the difference between them is as follows:
First look from the name:
UART: universal asynchronous receiver and transmitter
USART: universal synchronous asynchronous receiver and transmitter universal synchronous/asynchronous receiver and transmitter
As can be seen from the name, USART has added a synchronization function based on UART, that is, USART is an enhanced type of UART, which is indeed the case. But where has it been enhanced?
In fact, when we use USART for asynchronous communication, it is no different from UART, but when it is used for synchronous communication, the difference is obvious: everyone knows that synchronous communication requires a clock to trigger data transmission, which means that USART is relative to UART. One of the differences is that it can provide an active clock. For example, USART of STM32 can provide a smart card interface with clock support ISO7816.
Source: http://www.elecfans.com/baike/wuxian/20171108576890.html