![]() At the end of each data frame, the receiver stops briefly to wait for the next start bit. The receiver requires a shorter stop period than the transmitter. ![]() It cannot be shorter than a specified amount, usually 1 to 2 bit times. The "stop bit" is actually a "stop period" the stop period of the transmitter may be arbitrarily long. The number of data and formatting bits, the presence or absence of a parity bit, the form of parity (even or odd) and the transmission speed must be pre-agreed by the communicating parties. In this diagram, one byte is sent, consisting of a start bit, followed by eight data bits (D0-7), and two stop bit, for a 11-bit UART frame. However due to Ethernet's protocol overhead and minimum payload size of 42 bytes, if small messages of one or a few bytes are to be sent, Ethernet's protocol efficiency drops much lower than the UART's 8N1 constant efficiency of 80%.Įxample of a UART frame. For comparison, Ethernet's protocol efficiency when using maximum throughput frames with payload of 1500 bytes is up to 95% and up to 99% with 9000 byte jumbo frames. In the most common settings of 8 data bits, no parity and 1 stop bit (aka 8N1), the protocol efficiency is 80%. half duplex (devices take turns transmitting and receiving)ĭata framing UART frame, field length in Bits 1įor UART to work the following settings need to be the same on both the transmitting and receiving side:. ![]()
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