GE 369B1860G0028 Power board PLC processor module
Data communication mainly includes parallel communication and serial communication.
Parallel communication is a data transmission method based on bytes or words. In addition to 8 or 16 data lines and one common line, it also requires control lines for data communication. The transmission speed of parallel communication is fast, but the number of transmission lines is large and high, which is generally used for data transmission in a short distance. Parallel communication is generally used inside PLC, such as data communication between PLC internal components, between PLC host and expansion module, or between close intelligent modules. Serial communication is a data transmission method based on binary bit. Only one bit is transmitted at a time. In addition to the ground wire, only one data line is needed in one data transmission direction. This line serves as both a data line and a communication link control line. Data and link signals are transmitted bitwise on this line. Serial communication requires few signal lines, only two or three lines, which is suitable for the situation with long distance. Both computer and PLC are equipped with universal serial communication interface, and serial communication is generally used in industrial control. Serial communication is mostly used for data communication between PLC and computer and between multiple PLCs.
In serial communication, the transmission rate is usually expressed by bit rate (binary bits transmitted per second), and its unit is bit/second (bit/s) or bps. Transmission rate is an important index to evaluate communication speed. The commonly used standard transmission rates are 300, 600, 1200, 2400, 4800, 9600 and 19200bps. The transmission rates of different serial communications vary from hundreds of bps to 100Mbps. Simplex communication and duplex communication
Serial communication is divided into simplex and duplex modes according to the transmission direction of information between devices.
Simplex communication can only send or receive data in a single direction. The information of duplex communication mode can be transmitted in two directions. Each station can send and receive data.
Duplex mode is divided into full duplex and half duplex. The transmission and reception of data are transmitted by two or two sets of different data lines respectively. Both sides of the communication can receive and send information at the same time. This transmission mode is called full duplex mode; Use the same line or group of lines to receive and send data. Both sides of the communication can only send or receive data at the same time. This transmission mode is called half-duplex mode. Half duplex and full duplex communication are often used in PLC communication.
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