來源: UART
通用非同步收發傳輸器（Universal Asynchronous Receiver/Transmitter，通常稱作UART，讀音/ˈjuːɑrt/）是一種非同步收發傳輸器，是電腦硬體的一部分，將資料由序列傳輸（Serial communication）與平行傳輸（Parallel communication）間作傳輸轉換。UART通常用在與其他通訊協定（如EIA RS-232）的連結上。
| UART is an asynchronous communication protocol. A complete UART signal package must consists of START, DATA, Parity check, STOP, Buad, and TXD segments. |
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| UART Specification user-defined interface: | |
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| START | When TXD is changing form HIGH to LOW voltage (1 bit). | |
| DATA | Users must decide the size of signal package segment from 4 to 8bits. | |
| Parity Check | This performs three types of parity checks: odd-parity, even-parity, and no-parity. | |
| STOP | This occurs when TXD is at high voltage. This is adjustable; this is commonly set to 1 or 2. | |
| Baud | This is the data transmission speed according to the START initial condition. | |
| TXD | This is the transmission direction. It is LSM -> MSB by default. |
(Universal Asynchronous Receiver Transmitter) The electronic circuit that makes up the serial port. Also known as "universal serial asynchronous receiver transmitter" (USART), it converts parallel bytes from the CPU into serial bits for transmission, and vice versa. It generates and strips the start and stop bits appended to each character. Note that in the following paragraphs, dashes have been added after the 16 for readability. Older 8250 and 16-450 UARTs are not fast enough for today's modems. A 16-550 is required for transmission up to 115,200 bps (115 Kbps).
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