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This article is about what the rs-232c interface refers to. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

RS-232C is the interface for data exchange. The full name of RS-232C standard (protocol) is EIA-RS-232C standard, which is defined as the technical standard of serial binary data exchange interface between data terminal equipment (DTE) and data communication equipment (DCE).

The operating environment of this tutorial: windows7 system, Dell G3 computer.

RS-232C is the interface for data exchange.

The full name of RS-232C standard (protocol) is EIA-RS-232C standard, which is defined as the technical standard of serial binary data exchange interface between data terminal equipment (DTE) and data communication equipment (DCE).

It is a standard for serial communication developed by the American Electronic Industry Association (EIA) in conjunction with Bell systems, modem manufacturers and computer terminal manufacturers in 1970. EIA (Electronic Industry Association) represents the American Electronic Industry Association, RS (Recommended standard) represents the recommended standard, 232is the identification number, and C represents the latest revision of RS232.

Extended data:

The data transmission between computer and computer or between computer and terminal can be carried out in two ways: serial communication and parallel communication. Serial communication is widely used because of its few lines and low cost, especially in remote transmission, which avoids the inconsistent characteristics of multiple lines. In serial communication, both sides of the communication are required to use a standard interface, so that different devices can be easily connected to communicate.

RS-232-C interface (also known as EIA RS-232-C) is the most commonly used serial communication interface at present. It is a standard for serial communication made by the American Electronic Industry Association (EIA) in conjunction with Bell systems, modem manufacturers and computer terminal manufacturers in 1970. Its full name is "Technical Standard for Serial binary data Exchange Interface between data Terminal equipment (DTE) and data Communication equipment (DCE)". This standard provides for a 25-pin DB25 connector, which specifies the signal content of each pin of the connector and the level of various signal signals.

(1) the signal content of the interface in fact, many of the 25 leads of the RS-232-C are rarely used, and only 3-9 leads are generally used in the communication between the computer and the terminal. The signal content of the 9 most commonly used leads in RS-232-C

(2) the voltage of any signal line in RS-232-C is negative logic relation. Namely: logic "1",-5-- 15V; logic "0" + 5-+ 15V. The noise tolerance is 2V. That is, the receiver is required to recognize signals as low as + 3V as logic "0" and as high as-3V as logic "1".

(3) the physical structure of the interface RS-232-C interface connector generally uses the 25-core plug socket of the model DB-25, usually the plug is at the DCE end, and the socket is at the DTE end. The RS-232-C interface of some devices connected to the PC, because they do not use each other's transmission control signals, only need three interface lines, namely, "send data", "receive data" and "signal ground". Therefore, the 9-core plug seat of DB-9 is adopted, and the transmission line is shielded twisted pair.

(4) the length of transmission cable is stipulated by RS-232C standard. The length of transmission cable should be 50 feet when the symbol distortion is less than 4%. In fact, this 4% symbol distortion is very conservative. in practical application, about 99% of the users work in the range of 10-20% symbol distortion, so the maximum distance in practical use will be much more than 50 feet. The American DEC company has stipulated that the symbol distortion is allowed to be 10% to obtain the experimental results in schedule 2.

Among them, the No. 1 cable is a shielded cable, the model is DECP.NO.9107723, there are three pairs of twisted pair, each pair is composed of 2mm AWG, which is covered with a shielding net. Cable No. 2 is an unshielded cable. Model DECP.NO.9105856-04 is a quad-core cable for 22#AWG.

1. RS-232-C is a serial physical interface standard developed by EIA (Electronic Industry Association) of American Electronic Industry Association. RS is the abbreviation of "recommendation", 232is the identification number, and C is the number of changes. The RS-232-C bus standard has 25 signal lines, including a main channel and an auxiliary channel. In most cases, the main channel is mainly used. For general duplex communication, only a few signal lines are needed, such as a transmitting line, a receiving line and a ground wire.

The data transfer rate specified by the RS-232-C standard is 50,75,100,150,300,600,1200, 2400, 4800, 9600, 19200 baud per second. According to the RS-232-C standard, the driver is allowed to have a capacitive load of 2500pF, and the communication distance will be limited by this capacitance. For example, when using a 150pF/m communication cable, the maximum communication distance is 15m; if the capacitance of each meter of the cable decreases, the communication distance can be increased.

Another reason for the short transmission distance is that RS-232 is a single-ended signal transmission, which has some problems such as common ground noise and inability to suppress common-mode interference, so it is generally used for communications within 20m.

2. RS-485 bus, when the communication distance is tens of meters to thousands of meters, RS-485 serial bus standard is widely used. RS-485 uses balanced transmission and differential reception, so it has the ability to suppress common-mode interference. In addition, the bus transceiver has high sensitivity and can detect voltages as low as 200mV, so the transmitted signal can be recovered from kilometers away.

RS-485 works in half-duplex mode, and only one point can be transmitted at any time, so the transmitting circuit must be controlled by the enable signal. RS-485 is very convenient for multipoint interconnection and can save a lot of signal lines. The application of RS-485 can be connected to form a distributed system, which allows up to 32 drivers and 32 receivers to be connected in parallel.

In the past, PC communicates with intelligent devices by means of RS232, RS485, Ethernet and so on, which mainly depends on the interface specification of the device. However, RS232 and RS485 can only represent the physical media layer and link layer of communication. if we want to realize two-way access to data, we must write communication applications by ourselves, but most of these programs can not meet the specifications of ISO/OSI, and can only achieve a single function, which is suitable for a single device type, and the program is not universal.

In the equipment network of RS232 or RS485 equipment, if the number of devices exceeds 2, RS485 must be used as the communication medium. The exchange of information between devices in RS485 network can only be realized through the transfer of "master (Master)" devices, which is usually PC, but only one master device is allowed in this kind of equipment network, and the rest are all Slave devices. Fieldbus technology is based on ISO/OSI model and has a complete software support system, which can solve the problems of bus control, conflict detection, link maintenance and so on.

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