PROFIBUS is called process fieldbus. It consists of three compatible parts: PROFIBUS-DP (decentralized peripheral), Profibus-PA (process automation) and profibus-fms (Fieldbus message specification).
The transmission medium is shielded / unshielded twisted pair or optical fiber. The maximum transmission distance of twisted pair is 9.6km, and that of optical fiber is 90km;
The network topology is linear, tree or bus type with active terminal resistors at both ends. The communication mode is relatively simple: token passing between master stations and master-slave mode between slave stations;
The transmission rate varies from 9.6kb/s to 12MB / s. generally speaking, the slower the transmission rate is, the farther the effective transmission distance is; conversely, the faster the transmission rate is, the smaller the effective transmission distance is;
The maximum length of transmitted information is 255b, the maximum length of data is 244b, and the typical length is 120b;
Data transmission services include cyclic and non cyclic services.
2、 Configuration of PROFIBUS
1. Configure DP master station
In the hardware configuration stage, when configuring the board with PROFIBUS DP interface, the system will automatically pop up the configuration window, as shown in Figure 1. If it is not configured in the earlier stage, you can also right-click DP port and select “add master station system (a)”, or you can pop up the configuration window as shown in Figure 1. The configuration is relatively simple, just operate as shown in the figure. After configuration, as shown in Figure 2.
Figure 1 configuration of PROFIBUS
Figure 2 configuration of PROFIBUS
2. Linked slave station
In the application of S7-300 in industrial field distributed I / O, how to connect distributed I / O has been introduced. The connection method of other DP slave stations is similar, so it will not be repeated here. Here are some examples to introduce what was not mentioned in the last article.
Take an et200m slave station as an example. In the hardware configuration phase, we will assign a DP address to it. As shown in Figure 3, the DP address of et200m is 5. But only this is enough to “get through” the communication. We have to allocate station address 5 on the corresponding et200m on site. Et200m uses dial code to set the address, as shown in Figure 4. There are seven dialing codes, which are “1, 2, 4, 8, 32, 64” from bottom to top. Therefore, address 5 is about to be set to 5 by dialing the first and third dialing codes from bottom to top.
Figure 3 assign DP address
Figure 4 et200m address dialing
Setting station address by dialing code is a common method for many equipment, such as the following equipment that camel often contacts.
Figure 6 encoder
Figure 7Dp to RS232 device
In addition to dialing the code to set the station address, there are some devices that set the station address through parameters. For example, Siemens 6RA70 series rectifier and 6rs70 series frequency converter can be connected to PROFIBUS bus bus as slave station through CBP series office card, and their station address needs to be set through p918.
Figure 8 SIMOREG rectifier
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