Anti-static clothing and anti-static shoes are required for power supply testing of field devices.
The so-called global data communication is to realize a cyclical data transmission between each station in the MPI subnet. The communication process is executed by the system program, so no user programming is required, and no configuration is required, but sTEP 7 is required to use global data. (GD) is defined. The main contents of the definition include the CPU participating in the global data exchange, the data transmission area, the data receiving area, and the size of the data packet. Global data communication can only be carried out between S7-300/400 PLCs of the MPI network.
Before defining a global data package, the first thing to do is to set up an MPI subnet in STEP 7.
1. Configuring the MPI subnet
The general steps for building a subnet in STEP 7 are as follows.
1 Establish a project. .
2 Select the "Options" - "Configure Network" option in the SIMATIC Manager interface or double the MPI in the SIMATIC Manager interface to open the NetPro interface.
3 In the right window of the NetPro interface, open the Subnets folder and select the subnet type. There are 4 options: Indus—trial Ethernet (212~P2 too), MPI, Profibus, PTP, double-click the selected subnet, in the NetPro interface. The left window will learn the corresponding lines and indicate the type name. The colors of different subnets are different. Since the default subnet type of the STEP 7 project is MPI, this step can be omitted.
4 Also in the right window of the NetPro interface, open the Stations folder, double-click or drag the selected stations and place them in the left window VI.
5 In the left window of the NetPro interface, double-click the added station, you can directly enter the hardware configuration interface (HWConfig), according to the introduction in Chapter 7 of this book, perform hardware configuration for each station in turn.
6 In the left window of the NetPro interface, double-click the line indicating the MPI(1) subnet, and the Network Properties dialog box will pop up to set the transmission rate and maximum address. The MPI default transmission rate is 187.5kbps.
7 On the basis of, click on the small box indicating the MPI interface in each station (the color of which is the same as the color of the MPI subnet line), pop up the interface property dialog box (here, MPI interface), and select the subnet type. In the Properties dialog, NetPro has automatically assigned an MPI address and allows manual modification.
Or, if you click on the interface module directly, the module properties dialog box is displayed, in which the interface properties are selected.
After the previous steps, the establishment of an MPI subnet is completed. The main information contained in the following is:
2. Communication function block supporting S7 connection
Only S7-3. 0/400 cPu supports S7 communication. Bilateral communication can be realized between S7-400/400, s7-300/400 PLC can only achieve unilateral communication, S7-300 PLC is server, receive and respond to read/write operations from s7-400.
A communication function block that supports S7 connection (protocol). Note that since the three main types of subnets in SIMATIc support s7 communication, the contents listed in Table 10-2 are not limited to the MPI network.
Through the online help documentation of sTEP 7, you can learn the specific usage and precautions of each communication function block.
PG/OP communication is the most basic communication function of the MPI network. It is not necessary to perform any configuration and programming on the PLC side to realize this communication. When the operator panel or touch screen communicates with the PLc via MPI, the relevant communication parameters are configured on the operator panel or touch screen side using the PROTOOL configuration software.
Similarly, when the communication between WINCC and s7 PLC is realized by MPI, it is not necessary to configure and program on the PLC side. On the WINCC, the MPI station address, slot number and network card of the CPU should be configured. P, ofibu. (Process Field Bus) is a master-slave network that uses token bus technology for cell-level and field-level. It is an international, open, fieldbus standard that does not depend on device manufacturers. With the Profibus standard system, automation devices from different manufacturers exchange information via the same interface. Profibus is suitable for high-speed data exchange and high-time requirements.
The Profibus network is used to form a distributed control system, which can decompose complex automation tasks into several "subtasks" and form several subsystems. There is efficient and high-speed data exchange between subsystems, and the burden on each subsystem is small. The entire anti-static shoes and anti-static service system have a fast response speed and network redundancy.
Profibus consists of three compatible parts: Profibus-DP (Decentralized Periphery), Pro-fibUS-PA (Process Automation), Profibus-FMS (Fieldbus MessageSpecification), respectively Distributed I/O systems, process control systems, and industrial monitoring network systems for plant-level automation in industrial enterprise automation.
The physical layer of Profibus is RS-485, the transmission medium is shielded twisted pair cable (characteristic impedance 150~2), or fiber optic cable. When the shielded twisted pair cable is used, the topology of the Profibus network is basically the same as that of the MPI network. The antistatic shoes and the antistatic clothing are the same, and the terminal resistors are placed at both ends of one bus segment. The location of the "ON" - this is the same as the MPI network.
Profibus-PA uses transmission technology in accordance with IEC 1158-2 to ensure intrinsic safety. The power of field devices is provided by the bus. The transmission medium is shielded or unshielded twisted pair cable at a rate of 31.25 kbps. One RC terminator is connected to each end of the bus segment, and a 100fl resistor and a 1/F capacitor are connected in series.
The slaves of the Profibus PA are always connected to the DP/PA coupler and can be connected directly to the Profi-bus-DP network via the DP/PA coupler or to the DP network via the DP/PA Link.