Communication between the 300 CPUs includes MPI communication and DP communication. MPI communication has a maximum communication distance of 100 meters, while DP communication can achieve a single-segment communication distance of up to 1200 meters, allowing for longer data transmission distances. Both MPI and DP communication use a 485 interface. In an MPI communication network, data exchange between up to four 300 CPUs can be configured.
MPI global data communication uses a broadcast method for data exchange, which does not require programming of global data. It only requires configuring data communication in the STEP7 MPI network using a global data table.
For small to medium-sized production lines, communication between two to four 300CPU units can be achieved using MPI communication. The following describes the global data configuration method for MPI communication between two 300CPU units.
Hardware requirements: CPU315-2DP, CPU312
Software requirements: STEP7 programming software
1) Open the STEP7 programming software, create a project MPI TONGXUN, and insert two stations into the project: CPU312 station and CPU315-2DP station, as shown in the figure.
2) Configure the CPUs of the two stations separately, configure the MPI communication rate and station number. The communication rate can be selected from 19.2K to 12M. Here we select the system default communication rate: 187.5K, 312 CPU station: station 2, 315 CPU station: station 3. The configuration is as follows.
The CPU configuration for site 312 is shown below. The system defaults to address #2 and does not require modification:
The CPU configuration for site 315-2DP is shown in the following figure. In the "Properties" dialog box, the MPI network site address is defined as the address of site #3, as shown in the following figure:
300 CPU MPI Global Data Communication Configuration Method and Introduction
Next, we will configure global data communication. There are two methods:
Method 1: In the configured project, right-click the MPI network to set global variable data; as shown in Figure 1.
Method 2: Open any configured hardware configuration, click the configuration network icon "", right-click MPI to set global variable data, as shown in the following figure:
Define the data transmission and reception parameters. For inter-CPU communication, a maximum of four global data packet loops can be defined. The address area can be M, D, Q, or I, with a maximum length of 22 bytes. Defining multiple data areas, each occupying two bytes, will reduce the maximum 22-byte transmission and reception size accordingly. The address lengths of the transmission and reception areas must be consistent; otherwise, a compilation error will occur. (Forwarding code: Yiwei UN300 PLC)
The steps to define a global data send/receive area are shown in the following figure:
The global data transmission and reception area scan rate and global data status are defined as shown in the following figure:
The above describes the global data configuration method for two 300CPU MPI servers. The same configuration method applies to three or four servers. You can try configuring one yourself to see how it works.
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