The UART is a general purpose serial data bus for asynchronous communication. The bus bidirectional communication enables full duplex transmission and reception. In embedded design, the UART is used for communication between the host and the auxiliary device, such as communication between the car audio and the external AP, and communication with the PC includes communication with the monitor debugger and other devices such as EEPROM.
The function of the UART uses parallel data internally. It cannot directly send data to the modem. It must be UART-organized for asynchronous transmission. The process is: the CPU first puts the data to be written to the serial device into the UART register (temporary memory block). In the case, it is transferred to the serial device through the FIFO (First Input First Output). If there is no FIFO, the information will become messy and cannot be transmitted to the modem. It is a chip for controlling computers and serial devices. One thing to note is that it provides an RS-232C data terminal device interface so that the computer can communicate with a modem or other serial device that uses the RS-232C interface.
As part of the interface, the UART also provides the ability to convert parallel data transferred from within the computer into an output serial data stream. Serial data from outside the computer is converted to bytes for use by devices with parallel data within the computer. A parity bit is added to the output serial data stream, and a parity is received for the data stream received from the outside. A start and stop flag is added to the output data stream, and the start and stop flag is deleted from the received data stream. Handles interrupt signals from the keyboard or mouse (the keyboard and mouse are also serial devices).
To handle synchronization management issues between computers and external serial devices. Some of the more advanced UARTs also provide buffers for input and output data. The newer UART is the 16550, which stores 16 bytes of data in its buffer before the computer needs to process the data. The usual UART is 8250. If you buy a built-in modem, there will usually be a 16550 UART inside the modem.
USARTUniversal Synchronous/Asynchronous Serial Receiver/Transmitter USART is a full-duplex universal synchronous/asynchronous serial transceiver module that is a highly flexible serial communication device.
USART features
1. Full-duplex operation (receiving data and transmitting data independently of each other);
2. When the operation is synchronous, the host clock can be synchronized or the slave clock can be synchronized.
3. Independent high-precision baud rate generator, does not occupy the timer / counter;
4. Serial data structure supporting 5, 6, 7, 8, and 9-bit data bits, 1 or 2 stop bits;
5. Hardware-supported parity bit generation and verification;
6. Data overflow detection;
7. Frame error detection;
8. A detection noise filter and a digital low pass filter including an error start bit;
9. Three completely independent interrupts, TX transmission completed, TX transmit data register empty, RX reception completed;
10. Support multi-machine communication mode;
11. Support double speed asynchronous communication mode.
UART and USART are differentUART: universal asynchronous receiver and transmitter universal asynchronous transceiver
[Bus Signal] TX , RX
USART: universal synchronous asynchronous receiver and transmitter universal synchronous asynchronous transceiver
[Bus Signal] TX, RX, CK
The USART supports synchronous mode, so the USART needs to synchronize the always-on signal USART_CK (such as the STM32 microcontroller). Normally, the sync signal is rarely used, so the general MCU UART and USART are used in the same way, using asynchronous mode.
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