PLC communication, commonly used serial communication, Ethernet communication, fieldbus communication.
In serial communication, it is divided into D port and USB port. The D port is a nine-pin type, the needle is called a male port, and the mouth is called a female port. There are three protocols: RS232, RS422 and RS485. No communication protocol, the link method is not the same, so I won’t elaborate. Like the needle port of the computer, it is RS232, the round port of Mitsubishi PLC, RS422, Siemens PLC, RS485. Serial access, typically a point-to-point link, such as a PLC and one or more screens, does not allow multiple PLCs and multiple screens.
The communication protocol of the USB port is the same as that of the D port, but the D port can be soldered by itself, but the USB can only be purchased, and different manufacturers cannot be compatible.
The Ethernet communication port is the computer network port we have seen. It can be used with the network cable to distinguish the straight-through line and the cross-line. Ethernet communication, fast transmission speed, long distance, can be extended to fiber optic links, the distance is up to several kilometers, generally used for monitoring with the host computer.
There are many fieldbus categories. Now there are a total of 9 types in the entire electrical industry. The common bits are MOD and PROFIBUS. The protocols used are all confidential. Although the interfaces are all D ports (same as serial ports), the communication method is chosen. It has specificity and is mainly used to link multiple controllers in the field, such as multiple PLCs and multiple screens, allowing multiple master stations and slave stations.