Communication between bus interface and computer (III.) end-to-end asynchronous serial port

Introduction of Serial port

1. What is a serial port?

The serial port is a very common device communication protocol on the computer. The concept of serial communication is very simple, the serial port bitwise (BIT) Send and receive bytes. Although it is slower than parallel communication by Byte (byte), the serial port can receive data with another line while sending data using one line. The serial port can easily realize the long distance communication.

Spi,iic belongs to the synchronous serial port.

The UART belongs to the asynchronous serial port (Universal asynchronous Receiver and transmitter universal Asynchronous transceiver).

2. Asynchronous serial port Application line diagram

Typically, asynchronous serial communication uses 3?? Root line complete:?? (1) ground, (2) Send, (3) receive

3. Asynchronous serial port communication parameters

Baud rate, start bit, data bit, stop bit, and parity. For two ports to pass, these parameters must match.

1) Baud rate:

A) This is a parameter that measures the speed of communication. It represents the number of bits transmitted per second, usually the baud rate of the serial port is 9600,19200, 115200, 14400,28800 and 36600, etc.

b) The baud rate is inversely proportional to the distance

2) Starting bit:

The starting bit must be the logic "0" level that lasts a bit time, and the flag transmits the start of a character

3) Data bits:

This is the parameter that measures the actual data bits in the communication, and the standard values are 5, 7, and 8 bits

4) Stop bit:

Marks the end of the transmission of a character, expressed as a logical "1" level, typically with a value of 1, 1.5, and 2 bits (1.5 bits is the width of the time, representing 1.5 times times the bit.) For example, your baud rate is 1000bps, then the width of a bit is 1ms, a stop bit is 1ms, and 1.5 stop bit is 1.5ms.

5) parity Check bit:

A simple error-checking method in serial communication

A) odd check: artificially adds a check digit to the signal to ensure that the number of "1" in the sent signal is an odd number, such as: 0110,0101 1 0100,0000 0

b) Parity: Artificially adds a check digit to the signal to ensure that the number of "1" in the signal being sent is an even number, such as: 0100,0101 1 0100,0001 0

4. Asynchronous serial data transmission sequence diagram

(The idle bit indicates that the line is idle, at which point the line is a logic "1" level.) idle bit can not , at this time asynchronous transfer efficiency is highest)

5. Extended application of asynchronous serial port

References:

1. Common Interface Circuit Introduction http://wenku.baidu.com/link?url=rPXAWPV1DLttBOy6O2-8g4jq2VZBnv4v70bCixoCU6l2I6Yuc9reQ-I99_ Njimh1tvkolxskpucml65bx2-yelmnzxtbnd-cjf2ov60mwbk
2. Serial Communication Interface
3. Serial Communication-Communication protocol

Communication between bus interface and computer (III.) end-to-end asynchronous serial port