The serial interface is abbreviated as serial port, also called serial communication interface (usually referred to as COM interface). It is an expansion interface that uses serial communication. The communication method in which bit data of one message is transmitted bit by bit is called serial communication. The characteristics of serial communication are: data bits are transmitted and transmitted in bit-sequential order. At least one transmission line is required to complete. The cost is low but the delivery speed is slow. The distance of serial communication can be from a few meters to several kilometers; according to the direction of information transmission, serial communication can be further divided into simplex, half duplex and full duplex.
Serial Interface - Introduction The appearance of the serial port was around 1980, the data transmission rate was 115kbps ~ 230kbps. The initial stage of the serial port is to achieve the purpose of connecting the computer peripherals. The initial serial port is generally used to connect the mouse and external Modem and old-fashioned cameras and tablet devices. The serial port can also be used for connection and data transmission between two computers (or devices). Because the serial port (COM) does not support hot swap and the transmission rate is relatively low. Currently, some new motherboards and most portable computers have begun to cancel the interface. At present, serial ports are mostly used in industrial control and measurement equipment and some communication devices.
Serial Interface - Interface Division Standard The serial interface includes RS-232-C, RS-422, and RS485 according to electrical standards and protocols. The RS-232-C, RS-422, and RS-485 standards only specify the electrical characteristics of the interface and do not involve connectors, cables, or protocols.
RS-232: Also called standard serial port, the most commonly used serial communication interface. It was established in 1970 by the United States Electronic Industries Association (EIA) in conjunction with the Bell system, modem manufacturers and computer terminal manufacturers for the serial communication standard. Its full name is "a serial binary data exchange interface technology standard between data terminal equipment (DTE) and data communication equipment (DCE)." The traditional RS-232-C interface standard has 22 wires and uses a standard 25-pin D-type connector (DB25). Later, it is simplified to a 9-pin D-type socket (DB9). Nowadays, 25-pin connectors are rarely used. .
RS-232 adopts unbalanced transmission, so-called single-ended communication. Since the difference between the transmission level and the reception level is only about 2V to 3V, the common-mode rejection capability is poor. Together with the distributed capacitance on the twisted pair, the maximum transmission distance is about 15 meters and the maximum rate is 20kb. /s. RS-232 is designed for point-to-point (ie, only one pair of receiving and transmitting devices) communication, and its driver load is 3 ~ 7kΩ. So RS-232 is suitable for communication between local devices.
RS-422: The full name of the standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuits." It defines the characteristics of the interface circuit. A typical RS-422 is a four-wire interface. There is actually a signal ground, a total of 5 lines. Its DB9 connector pin definition. Since the receiver uses a high input impedance and the transmission driver has stronger driving capability than RS232, multiple receiver nodes can be connected on the same transmission line, and up to 10 nodes can be connected. That is, one master device (Master) and the rest are slave devices (Salve). The slave devices cannot communicate with each other. Therefore, RS-422 supports point-to-multipoint bidirectional communication. The input impedance of the receiver is 4k, so the maximum load capacity of the transmitter is 10×4k+100Ω (terminating resistor). Because the RS-422 4-wire interface uses separate transmit and receive channels, there is no need to control the data direction. Any necessary handshake between devices can be handled either in software (XON/XOFF handshaking) or hardware (pairs of individual pairs) Stranded) implementation.
The maximum transmission distance of RS-422 is 1219 meters and the maximum transmission rate is 10Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, the maximum transmission distance is possible. The highest rate transmission can only be achieved at a short distance. The maximum transmission rate that can be obtained on a typical 100-meter long twisted pair is only 1 Mb/s.
RS-485: Based on RS-422, many RS-485 electrical specifications are similar to RS-422. If you use balanced transmission methods, you need to connect termination resistors on the transmission line. RS-485 can use two-wire and four-wire, two-wire system can achieve true multi-point two-way communication, and using four-wire connection, like RS-422 can only achieve point-to-multipoint communication, that can only have one main ( (Master) equipment, the rest is slave equipment, but it is improved compared to RS-422. There are 32 devices on the bus whether four-wire or two-wire connection.
RS-485 differs from RS-422 in that its common-mode output voltage is different, RS-485 is between -7V and +12V, RS-422 is between -7V and +7V, and RS-485 receiver The minimum input impedance is 12kΩ and S-422 is 4kΩ. Since S-485 satisfies all RS-422 specifications, RS-485 drivers can be used in RS-422 networks.
RS-485, like RS-422, has a maximum transmission distance of approximately 1219 meters and a maximum transmission rate of 10 Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, it is possible to use the longest specified cable length. The highest rate transmission can only be achieved at a short distance. The maximum transfer rate of a 100-meter long twisted pair is only 1Mb/s
Serial Interface - Introduction The appearance of the serial port was around 1980, the data transmission rate was 115kbps ~ 230kbps. The initial stage of the serial port is to achieve the purpose of connecting the computer peripherals. The initial serial port is generally used to connect the mouse and external Modem and old-fashioned cameras and tablet devices. The serial port can also be used for connection and data transmission between two computers (or devices). Because the serial port (COM) does not support hot swap and the transmission rate is relatively low. Currently, some new motherboards and most portable computers have begun to cancel the interface. At present, serial ports are mostly used in industrial control and measurement equipment and some communication devices.
Serial Interface - Interface Division Standard The serial interface includes RS-232-C, RS-422, and RS485 according to electrical standards and protocols. The RS-232-C, RS-422, and RS-485 standards only specify the electrical characteristics of the interface and do not involve connectors, cables, or protocols.
RS-232: Also called standard serial port, the most commonly used serial communication interface. It was established in 1970 by the United States Electronic Industries Association (EIA) in conjunction with the Bell system, modem manufacturers and computer terminal manufacturers for the serial communication standard. Its full name is "a serial binary data exchange interface technology standard between data terminal equipment (DTE) and data communication equipment (DCE)." The traditional RS-232-C interface standard has 22 wires and uses a standard 25-pin D-type connector (DB25). Later, it is simplified to a 9-pin D-type socket (DB9). Nowadays, 25-pin connectors are rarely used. .
RS-232 adopts unbalanced transmission, so-called single-ended communication. Since the difference between the transmission level and the reception level is only about 2V to 3V, the common-mode rejection capability is poor. Together with the distributed capacitance on the twisted pair, the maximum transmission distance is about 15 meters and the maximum rate is 20kb. /s. RS-232 is designed for point-to-point (ie, only one pair of receiving and transmitting devices) communication, and its driver load is 3 ~ 7kΩ. So RS-232 is suitable for communication between local devices.
RS-422: The full name of the standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuits." It defines the characteristics of the interface circuit. A typical RS-422 is a four-wire interface. There is actually a signal ground, a total of 5 lines. Its DB9 connector pin definition. Since the receiver uses a high input impedance and the transmission driver has stronger driving capability than RS232, multiple receiver nodes can be connected on the same transmission line, and up to 10 nodes can be connected. That is, one master device (Master) and the rest are slave devices (Salve). The slave devices cannot communicate with each other. Therefore, RS-422 supports point-to-multipoint bidirectional communication. The input impedance of the receiver is 4k, so the maximum load capacity of the transmitter is 10×4k+100Ω (terminating resistor). Because the RS-422 4-wire interface uses separate transmit and receive channels, there is no need to control the data direction. Any necessary handshake between devices can be handled either in software (XON/XOFF handshaking) or hardware (pairs of individual pairs) Stranded) implementation.
The maximum transmission distance of RS-422 is 1219 meters and the maximum transmission rate is 10Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, the maximum transmission distance is possible. The highest rate transmission can only be achieved at a short distance. The maximum transmission rate that can be obtained on a typical 100-meter long twisted pair is only 1 Mb/s.
RS-485: Based on RS-422, many RS-485 electrical specifications are similar to RS-422. If you use balanced transmission methods, you need to connect termination resistors on the transmission line. RS-485 can use two-wire and four-wire, two-wire system can achieve true multi-point two-way communication, and using four-wire connection, like RS-422 can only achieve point-to-multipoint communication, that can only have one main ( (Master) equipment, the rest is slave equipment, but it is improved compared to RS-422. There are 32 devices on the bus whether four-wire or two-wire connection.
RS-485 differs from RS-422 in that its common-mode output voltage is different, RS-485 is between -7V and +12V, RS-422 is between -7V and +7V, and RS-485 receiver The minimum input impedance is 12kΩ and S-422 is 4kΩ. Since S-485 satisfies all RS-422 specifications, RS-485 drivers can be used in RS-422 networks.
RS-485, like RS-422, has a maximum transmission distance of approximately 1219 meters and a maximum transmission rate of 10 Mb/s. The length of the balanced twisted pair is inversely proportional to the transmission rate. Below 100 kb/s, it is possible to use the longest specified cable length. The highest rate transmission can only be achieved at a short distance. The maximum transfer rate of a 100-meter long twisted pair is only 1Mb/s
Dynamic switching device is a non-contact, high reliability and fast switching switch used in dynamic power factor compensation equipment. It is especially suitable for fast and wear-free switching occasions. Typical applications include lifting equipment, elevators, electric welding machines and other occasions with frequent reactive power changes
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