INTELLIX MO150 变压器监测系统 具有成本效益的系统解决方案

PLC network is composed of multiple subnets, the communication process of each subnet is determined by the communication protocol, the communication mode is the core content of the communication protocol. So the PLC programming network communication mode has several?

1. Periodic I/O communication mode

Periodic I/O communication is often used in remote I/O links of programmable controllers. The remote I/O link works in master-slave mode, with the PLC remote I/O master unit as the master station and other remote I/O units as the slave station. The communication processor in the master station exchanges data with each slave station in turn by means of periodic scanning, sends the data sent from the corresponding sub-box to the slave station, and reads the data from the slave station and puts it into the receiving sub-box of the corresponding sub-box. In this way, the “remote input/output buffer” in the master station is flushed periodically.

2. Global I/O communication mode

Global I/O communication mode is the communication mode of serial shared storage area, which is mainly used for communication between PLC with linked area. In the global I/O communication mode, PLC directly reads and writes the link area with read and write instructions. The write operation of an address in one PLC can only read the same address in other PLC. Like the periodic I/O mode, the global I/O mode occupies the I/O area of the PLC and is therefore only suitable for small amounts of data communication.

3. Master/slave bus communication mode

Master/slave bus communication mode, also known as 1:N communication mode, means that there are N stations in the PLC subnet of the bus structure, of which only one master station, the rest are slave stations. The central access control technology is used to allocate the bus access rights. The polling table is usually used to allocate the bus access rights.

4. Token Bus communication mode

Token bus communication mode, also known as N:N communication mode, refers to the PLC subnet of the bus structure has N stations, the status is equal, there is no difference between the master station and the slave station. You could also say that N stations are all primary stations.

N:N communication mode adopts token bus access control technology. The token-bus access control method limits how long each site can hold the token, ensuring that each site has the opportunity to acquire the bus right. Compared with the non-responsive data transmission mode, the response time of the responsive data transmission mode is significantly longer and the real-time performance is lower.

5. Floating master station communication mode

The communication mode of floating master station, also known as N:M communication mode, is suitable for PLC network with bus structure, that is, there are M stations on the bus, wherein N(n< m= master station, and the rest are slave stations.

N:M communication mode adopts the access control technology combining token bus and master-slave bus. Firstly, N master stations are formed into a logical loop, in which tokens flow in turn and bus use rights are distributed among N master stations. The master station that has been granted access to the bus determines which stations to communicate with for its own token retention time based on the master-slave pattern.