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Difference Of USB Port, Serial Port And Parallel Port
- Sep 19, 2018 -

The serial port is called the serial interface. Today's PCs usually have two serial ports COM 1 and COM 2. The serial port differs from the parallel port in that its data and control information are transmitted one by one. Although this speed will be slower, the transmission distance is longer than the parallel port, so the serial port should be used for long distance communication. Usually COM 1 uses a 9-pin D-shaped connector, also known as the RS-232 interface, while COM 2 uses an old-fashioned DB25-pin connector, also known as the RS-422 interface. It has been rarely used.

The parallel port is also called the parallel interface. Currently, the parallel interface is primarily used as a printer port, using a 25-pin D-connector. The so-called "parallel" means that 8-bit data is simultaneously transmitted through parallel wire, so that the data transfer speed is greatly improved, but the length of the line for parallel transmission is limited, because the length is increased, the interference is increased, and the data is prone to error. At present, computers are basically equipped with parallel ports.

USB (Universal Serial Bus), commonly referred to as Universal Serial Bus, is designed to address the interface and ease of use of interface devices. USB was originally designed to connect to a variety of different interface devices, and for medium and low-speed interface devices, so USB transmission speed is not high. USB has two transmission rates, the first is full speed mode, the highest transmission rate can reach 12Mbps, the second is low speed mode, the transmission rate is 1.5Mbps. The low speed mode has only a few peripherals to use, and its only benefit is lower electromagnetic interference (EMI). Therefore, the USB full-speed transmission speed is quite high compared to the existing serial port (standard is 115200 bps), but when there are many peripheral connections, the overall performance may be degraded. In addition, USB is also very convenient to use, is to support hot swap, if the operating system has installed the device driver, you can directly install or remove the system when the system is running, unlike many devices must be the system power Close, or the operating system can be re-opened to use, which makes the convenience of use a lot.

On the other hand, the transmission way is different. The simplest difference is that the serial port is the widest and largest, the second port is the second, and the USB interface is the smallest. Therefore, the previous serial port parallel port is currently only used by some old printers, most of which are changed to USB, USB transmission. The fastest and the smallest is the most convenient.