What interface is com1?

com1 is a COM interface, which is a serial communication port. It is an expansion interface that uses serial communication; usually COM1 uses a 9-pin D-shaped connector, also called the RS-232 interface. The data and control information of the COM interface are transmitted bit by bit. Its characteristic is that the communication line is simple. As long as a pair of transmission lines are needed, two-way communication can be achieved (the telephone line can be directly used as the transmission line), thus greatly reducing the cost. Especially suitable for long-distance communication, but the transmission speed is slow.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

COM1 is a COM port (Component Object Mode interface, a standard interface defined by Microsoft), which is a serial communication port, or serial port for short. It is an expansion interface that uses serial communication.

The serial port is called the serial interface. Today's PCs generally have two serial ports COM 1 and COM 2. The serial port is different from the parallel port in that its data and control information are transmitted bit by bit. Although the speed will be slower, the transmission distance is longer than the parallel port, so if you want to communicate over a longer distance, you should use the serial port. Usually COM 1 uses a 9-pin D-shaped connector, also called the RS-232 interface, while COM 2 sometimes uses the old DB25-pin connector, also called the RS-422 interface. This interface is currently Already rarely used.

Serial Interface (Serial Interface) refers to the sequential transmission of data bit by bit. It is characterized by simple communication lines. As long as a pair of transmission lines, two-way communication can be achieved ( Telephone lines can be directly used as transmission lines), thus greatly reducing costs, and are especially suitable for long-distance communications, but the transmission speed is slow. The communication method in which each bit of data of a message is transmitted bit by bit in sequence is called serial communication. The characteristics of serial communication are: the transmission of data bits is carried out in bit order and can be completed with at least one transmission line; the cost is low but the transmission speed is slow. The distance of serial communication can range from a few meters to several kilometers; according to the direction of information transmission, serial communication can be further divided into three types: simplex, half-duplex and full-duplex.

The serial port appeared around 1980, and the data transmission rate is 115kbps~230kbps. The initial appearance of serial ports was for the purpose of connecting computer peripherals. In the early days, serial ports were generally used to connect devices such as mice and external modems, as well as old-fashioned cameras and writing pads. Serial ports can also be used for interconnection and data transmission between two computers (or devices). Since the serial port (COM) does not support hot swapping and has a low transmission rate, some new motherboards and most portable computers have begun to cancel this interface. Serial ports are mostly used in industrial control and measurement equipment and some communication equipment.

The difference between serial port and parallel port

The serial port can be described as one lane, while the parallel port has 8 lanes that can transmit 8 bits (one byte) of data at the same time. But this does not mean that the parallel port is fast. Due to the mutual interference (crosstalk) between 8-bit channels, the transmission speed is limited and the transmission is prone to errors. The serial ports do not interfere with each other. The amount of data sent simultaneously by the parallel port is large, but it is slower than the serial port. This is how serial hard drives are valued by people.

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