In UART: Start bit, stop bit, which defines the check bit, data bit, data bit, baud rate, and data communication interface.

From: http://hi.baidu.com/liang888%BA%C3/blog/item/38ad3351defc6711377abec2.html

Start position: sends a logic "0" signal, indicating the start of the transmission character. Data bit: After the start bit. The number of data bits can be 4, 5, 6, 7, 8, and so on. Generally, ASCII code is used. Transmits data starting from the second BIT and locates it by the clock. Parity bit: After the data bit is added, the "1" digit should be an even number (even verification) or an odd number (odd verification) to verify the correctness of data transmission. Stop bit: it is the end sign of a character data. It can be 1-bit, 1.5-bit, or 2-bit high. Idle bit: In the logical "1" status, indicating that there is no data transfer on the current line. Baud Rate: a pointer to the data transfer rate. The number of binary digits transmitted per second. For example, if the data transfer rate is 120 characters/second, and each character is 10 characters, the Transmission baud rate is 10 × 120 = 1200 characters/second = 1200 Potter.