Supervisory Control and Data Acquisition (SCADA) is an indispensable part of modern industrial control systems, responsible for monitoring and controlling various aspects of industrial processes.

The Programmable Logic Controller (PLC) is the core device for implementing automation control. In practical applications, communication between the upper computer and PLC is crucial.

This article will explore how to achieve communication between the upper computer and PLC through a network port.

1. Overview

In modern industrial processes, the upper computer serves as the brain of the control system, responsible for monitoring and scheduling the PLC. PLC achieves automation control of industrial processes by connecting various external devices such as sensors and actuators.
Therefore, communication between the upper computer and PLC is essential, as it can provide real-time data exchange and control instruction transmission.

2. Network port communication protocol
In order to achieve communication between the upper computer and PLC, it is necessary to choose a suitable communication protocol. At present, commonly used communication protocols include Modbus, Ethernet/IP, OPC, etc. These protocols are based on the TCP/IP protocol stack and can transmit data quickly and reliably.

3. Hardware connection
Before communication between the upper computer and PLC, hardware connection is required. Generally speaking, the upper computer and PLC are connected through a network port. Usually, both the upper computer and PLC are equipped with Ethernet interfaces, which are connected to the same local area network through Ethernet cables.

4. Set IP address
In order to achieve communication between the upper computer and PLC, IP addresses need to be assigned to them. Generally speaking, both the upper computer and PLC can set IP addresses through menus or software. When setting the IP address, it is necessary to ensure that the upper computer and PLC are in the same subnet and that the IP addresses do not conflict.

5. Configure communication parameters
Before communicating between the upper computer and PLC, it is necessary to configure the communication parameters. The specific configuration process may vary depending on the selected communication protocol. Taking Modbus protocol as an example, it is usually necessary to set parameters such as Modbus address and communication port of PLC.

6. Write communication programs
Once the hardware connection and parameter configuration are completed, the communication program can be written. Usually, both the upper computer and PLC provide corresponding development tools and interface libraries for the development of communication programs.

7. Data exchange
After communication through the network port, the upper computer and PLC can exchange data. This means that the upper computer can read the input signals of the PLC and obtain real-time measurement data from various sensors. At the same time, the upper computer can also send control instructions to the PLC to achieve control of external actuators.

8. Data processing

The communication between the upper computer and PLC is not limited to data reading and writing, but can also perform more complex data processing. For example, the upper computer can monitor and analyze the data obtained from the PLC in real time, thereby achieving fault diagnosis and predictive maintenance.

9. Security considerations
Security is a very important issue when communicating between the upper computer and PLC. To ensure the security of communication, some measures can be taken, such as setting access passwords, restricting network access, etc.

In summary, communication between the upper computer and PLC through Ethernet ports is an indispensable part of modern industrial control systems. Through appropriate communication protocols, hardware connections, and parameter configurations, the upper computer can exchange data with the PLC

And transmit control instructions. This provides convenience for monitoring and scheduling industrial processes, while also offering more possibilities for data processing and security considerations.