Abstract: This chapter mainly introduces the basic concepts of communication
1. Serial communication and parallel communication
Serial communication refers to a communication method that transmits data one by one in the form of data bits through a small number of data signal lines (generally less than 8), ground lines and control signal lines between devices.
Serial communication includes USART, I2C, SPI, etc.
Parallel communication generally refers to a communication method that uses 8, 16, 32, and 64 or more data lines for transmission. Parallel communication has SDIO (4 bits), FSMC (16 bits, control liquid crystal or display memory SRAM).
2. Full-duplex, half-duplex and simplex communication
According to the direction of data communication, communication is divided into full-duplex, half-duplex and simplex communication, which are mainly distinguished by the direction of the channel
3. Synchronous communication and asynchronous communication
According to the data synchronization mode of communication, it is divided into two types: synchronous and asynchronous. It can be distinguished simply according to whether the clock signal is used in the communication process.
4. Communication rate
A very important parameter to measure communication performance is the communication rate, which is usually expressed in terms of bit rate, that is, the number of binary digits transmitted per second, in units of bits per second (bit/s). The concept that is easily confused with bit rate is "Baudrate", which represents how many symbols are transmitted per second. The symbol is the concept of communication signal modulation. Symbols with the same time interval are often used in communication to represent a binary number. Such signals are called symbols.
For example, in common communication transmission, 0V is used to represent the number 0 and 5V to represent the number 1. Then a symbol can represent two states 0 and 1, so a symbol is equal to a binary bit. At this time, the size of the baud rate and the bit The rate is the same; if in the communication transmission, 0V, 2V, 4V and 6V represent binary numbers 00, 01, 10, 11 respectively, then each symbol can represent four states, namely two binary bits, so the symbol The number is half of the number of binary bits, and the baud rate at this time is half of the bit rate. Because a symbol in many common communications represents two states, people often directly express the bit rate by the baud rate