What does rs-232c interface mean?

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

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

RS-232C is the interface for data exchange.

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

It is a standard for serial communications jointly developed by the Electronic Industries Association (EIA) in 1970 in conjunction with the Bell System, modem manufacturers and computer terminal manufacturers. Among them, EIA (Electronic Industry Association) represents the American Electronics Industry Association, RS (Recommended standard) represents the recommended standard, 232 is the identification number, and C represents the latest modification of RS232.

Extended information:

Data transmission between computers or computers and terminals can use two methods: serial communication and parallel communication. The serial communication method is widely used because it uses fewer lines and is low-cost, especially in long-distance transmission, because it avoids the inconsistency of the characteristics of multiple lines. In serial communication, both communicating parties are required to use a standard interface so that different devices can be easily connected for communication.

RS-232-C interface (also known as EIA RS-232-C) is currently the most commonly used serial communication interface. It is a standard for serial communications developed in 1970 by the Electronic Industries Association (EIA) in conjunction with the Bell System, modem manufacturers and computer terminal manufacturers. Its full name is "Technical Standard for Serial Binary Data Exchange Interface between Data Terminal Equipment (DTE) and Data Communications Equipment (DCE)." The standard specifies the use of a 25-pin DB25 connector, with each pin of the connector The signal content of the pin is specified, and the levels of various signals are also specified.

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

(2) Electrical characteristics of the interface In RS-232-C, the voltage of any signal line has a negative logic relationship. That is: logic "1", -5--15V; logic "0" 5-15V. Noise margin is 2V. That is, the receiver is required to recognize signals as low as 3V as logical "0", and signals as high as -3V as logical "1"

(3) Physical structure of the interface RS-232-C interface connector is generally Use a 25-pin plug socket model DB-25, usually the plug is at the DCE end and the socket is at the DTE end. Some devices use the RS-232-C interface connected to the PC because they do not use the other party's transmission control signal, so only three interfaces are needed Lines, namely "send data", "receive data" and "signal ground". Therefore, the 9-pin plug socket of DB-9 is used, and the transmission line uses shielded twisted pair.

(4) The length of the transmission cable is stipulated by the RS-232C standard. When the code element distortion is less than 4%, the transmission cable length should be 50 feet. In fact, this 4% code element distortion is very conservative. In actual applications, about 99% of users work in the range of 10-20% code element distortion, so the maximum distance in actual use will be far more than 50 feet. The American DEC company has stipulated that the code element distortion is allowed to be 10% and The experimental results in Appendix Table 2 are obtained.

The No. 1 cable is a shielded cable, model DECP.NO.9107723. There are three pairs of twisted pairs, each pair is composed of 22# AWG, and is covered with a shielding net. Cable No. 2 is an unshielded cable. Model DECP.NO.9105856-04 is a 22#AWG four-core cable.

1. RS-232-C is a serial physical interface standard formulated by the Electronic Industry Association (EIA). RS is the abbreviation of "Recommended Standard" in English, 232 is the identification number, and C represents the number of revisions. 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 can be achieved, such as one Transmitting line, a receiving line and a ground line.

The data transmission rates specified by the RS-232-C standard are 50, 75, 100, 150, 300, 600, 1200, 2400, 4800, 9600, and 19200 baud per second. The RS-232-C standard stipulates that 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 per meter of cable is reduced , 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 problems such as common ground noise and the inability to suppress common mode interference. Therefore, it is generally used for communications within 20m.

2. RS-485 bus. When the communication distance is required to be tens of meters to thousands of meters, the 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 thousands of meters away.

RS-485 uses half-duplex working mode. Only one point can be in the sending state at any time. Therefore, the sending circuit must be controlled by the enable signal. RS-485 is very convenient for multi-point interconnection and can save many signal lines. RS-485 can be used to network to form a distributed system, which allows up to 32 drivers and 32 receivers to be connected in parallel.

In the past, communication between PCs and smart devices mostly relied on RS232, RS485, Ethernet and other methods, which mainly depended on the interface specifications of the device. However, RS232 and RS485 can only represent the physical media layer and link layer of communication. If you want to achieve two-way access to data, you must write your own communication application program. However, most of these programs cannot comply with ISO/OSI specifications and can only achieve A relatively single function, suitable for a single device type, and the program is not universal.

In a device network connected by RS232 or RS485 devices, if the number of devices exceeds 2, RS485 must be used as the communication medium. If the devices in the RS485 network want to exchange information, they can only communicate through the "Master" Device transfer can only be achieved. The master device is usually a PC. Only one master device is allowed in this device network, and the rest are all slave devices. Fieldbus technology is based on the ISO/OSI model and has a complete software support system that can solve problems such as bus control, conflict detection, and link maintenance.

For more computer-related knowledge, please visit the FAQ column!

The above is the detailed content of What does rs-232c interface mean?. For more information, please follow other related articles on the PHP Chinese website!