Whether it is the PLC programming of the 200 series or the PLC programming of the 300 series, the scope involved is generally the data changes inside the CPU, or the communication between various modules, so how do the CPUs of two different series PLCs communicate? To figure this out. 

Whether it is the PLC programming of the 200 series or the PLC programming of the 300 series, the scope involved is generally the data changes inside the CPU, or the communication between various modules, so how do the CPUs of two different series PLCs communicate? 

To understand this issue, you need to first understand a little about PROFIBUS-DP communication. How should PROFIBUS-DP communication be undertaken? First of all, it is an open fieldbus that complies with European and international standards. In the past, twisted pair shielded cables, optical cables or mixed configurations have been used to install various nodes to form a network system. Active nodes accept access to the network through token transfers, while driven nodes are assigned through polling of modules. Thus, this network is defined as the nature of master-slave communication. 

This allows the S7-200PLC to communicate with the S7-300 via a GSD file that supports PROFIBUS-DP communication. Here's how to do it: 

1. First, the hardware configuration is carried out in the S7-300PLC. As shown on the left side of Figure 1 below. 

 2. Configure the GSD file into the PROFIBUS DP network of the PLC 300CPU.

Network settings first: Double-click the CPU in the figure below, find the attributes in the pop-up window, set the corresponding parameters, and establish a new DP network. Then install the GSD file (as shown below).

Once installed, an important step in communicating between the PLC 300 CPU and the 200 CPU: locate the EM277 slave station in the selection list on the right and connect it to the DP bus. As shown in the figure below.

3. Double-click the EM277 slave in the above picture, and set the corresponding storage area in the pop-up window (V area in PLC200 corresponds to 300 and M area in PLC), which are used to send and receive data between PLC-200 and PLC-300. Then you can write debugging programs for receiving and transmitting in PLC-CPU200 and PLC-CPU300 respectively to perform data transmission. 

Note that the position of the dial switch on the EM277 in the actual operation of the PLC should be consistent with the address in the S7-300 configuration. That's the whole process. Follow me to give you absolute dry goods sharing!