one. system design
In the automatic control project of a factory, two Siemens S7-300 control system equipments separated by 3 km are required to exchange data. Because of the distance between the two devices, and the separation of mountains, the use of Ethernet fiber transmission is not realistic, given BANNER's excellent ultra-long-range wireless sensor products, designed using DataRadio radio station DX80DR2M in its surecross series. At the same time, since the two S7-300 control systems are all CPU315-2PN/DP controllers with Profibus-DP master interface, and the radio station DX80DR2M supports RS485 Modbus RTU protocol, we design the NT30-DPS from Hilscher. Gateway (Modbus RTU to Profibus-DP slave) to achieve data exchange, the system structure is designed as follows:
two. Functional description
As shown in Figure 1, the NT30-DPSs of the two remote stations are connected to the Profibus-DP bus of the CPU315-2PN/DP via their Profibus-DP interface as DP slaves, and their RS485 output lines are connected to the DX80DR2M radio. In order to implement master-slave data exchange for Modbus RTU, one NT30-DPS is designed to operate as a Modbus RTU master and the other NT30-DPS is designed to operate as a Modbus RTU slave. When the system is running, the Modbus RTU master gateway automatically reads and writes the register data of the Modbus RTU slave gateway according to the preconfigured communication command table (Modbus RTU commands FC1-FC16), and then each gateway in turn outputs the image area through Profibus-DP. Data exchange with the respective CPU315-2PN/DP master station to achieve data exchange between CPU315-2PN/DP, data exchange as shown below:
Figure 2: Data Exchange Implementation
As shown in the above figure, two NT30-DPS and their respective CPU315-2PN/DP achieve 64 bytes of input and output data exchange, and the communication mechanism is as follows:
1) The output data QW0-QW62 from the right CPU 315-2PN/DP is automatically transferred to the input register of the NT30-DPS as a Modbus RTU slave via the Profibus-DP mechanism, and then used as the Modbus RTU master station. The NT30-DPS is read into the register Register 1-32 through the FC4 function number, and is then automatically transferred to the IW0-IW62 input image area of ​​the CPU315-2PN/DP on the left via the Profibus-DP mechanism, thus implementing the right CPU. The output data is transferred to the left CPU's input data.
2) The output data QW0-QW62 from the left CPU 315-2PN/DP is automatically transferred to the output register Register 1-32 of the NT30-DPS as a Modbus RTU master via the Profibus-DP mechanism, and then the data is passed through function number 16. Writes to the holding register of the NT30-DPS as a Modbus RTU slave, and is finally transferred to the IW0-IW62 input image area of ​​the right CPU 315-2PN/DP through the Profibus-DP mechanism, thus realizing the left The output data of the side CPU is transferred to the input data of the right CPU.
As mentioned above, the data exchange between the CPU315-2PN/DP and the gateway is done automatically by the Profibus-DP mechanism, and the data transfer between the two gateways as the master and the slave of the Modbus RTU is preset via the configuration command of the master station. Therefore, for the CPU315-2PN/DP at both ends, the entire data exchange is realized without writing any program.
three. NT30-DPS parameter configuration
The parameter configuration of NT30-DPS is implemented by Hirschler SYCON.net software. The configuration parameters of NT30-DPS as Modbus RTU master station are as follows:
1) MODBUS table
2) SUPERVIS table
Supervision Mode SlaveError
The parameters not listed above use the default parameters.
For the NT30-DPS as a Modbus RTU slave, the configuration parameters are as follows:
1) MODBUS table
2) MODULES table
3) COMMAND table
No command
The parameters not listed above use the default parameters.
be careful:
1) No matter master-slave station should use ModbusRTU standard address format, ie address;
2) The allocation space of the MODULES address of the master and slave must be the same. The above is allocated 64 bytes of input and 64 bytes of output;
3) For the master station, its supervisor Mode parameter cannot be selected off, otherwise if a slave station in the multi-slave network communication fails (such as disconnected from the network), then the master gateway will not automatically skip the failed slave. Station (always try to communicate with the failed slave until it resumes communication);
four. Configuration in STEP7
To connect the NT30-DPS to the Profibus-DP network of the CPU315-2PN/DP, you must configure the network hardware in Siemens STEP7 software. First of all, in order to be able to find the NT30-DPS gateway in STEP7's Hardware Catalog, the NT30-DPS GSD file must be installed:
1) Insert the random CD of the NT30-DPS Gateway into the CD-ROM drive;
2) Close all current projects in STEP7's Hardware window, then select the menu Options->Install GSD File. In the dialog box that pops up, select the GSD file on the CD (in the GSD\PROFIBUS directory), and then click the Install button;
After installing the GSD file, you can configure the slave of Profibus: Open the Hardware window of STEP7, select the NT30-DPS gateway (under PROFIBUSDP\Additional Field Devices\Gateway) from the right catalog, and then drag it to the CPU Profibus on the left side. Finally set the Profibus address and input/output image area of ​​the NT30-DPS; the hardware configuration of STEP7 is shown in the following figure (CPU313C-2DP is used):
Fives. Application notes
1) There is a +5 VDC power supply on the RS485 pin of the NT30-DPS, so there should be no short circuit between all but the pink and gray lines (P and N of RS485) and the yellow line (ground), otherwise it will affect the communication. Or even burn out the communication port. For details, please refer to the hardware manual in the CD-ROM box.
2) If the STA indicator of the NT30-DPS is on, the NT30-DPS has established a connection with the Profibus-DP master;
3) After modifying the Profibus address of the NT30-DPS (set by the address disk number on the NT30-DPS), it is necessary to power on again;
4) The newly-manufactured NT30-DPS needs to be downloaded before use (downloaded in SYCON.net software);
six. Conclusion
Hirsch Automation Systems GmbH is an expert in the field of industrial network communications in the world. In addition to the PROFIBUS-to-serial port mentioned above, it also provides various fieldbuses, real-time Ethernet and serial ports, as well as user-defined serial protocol conversion gateways. Various serial devices are connected to the upper control network to realize device networking. Wuxi Beichen Automation Technology Co., Ltd. is the distributor of Germany Hilscher in East China. We are happy to provide the best solution for any network communication project in the field of industrial automation. This case was supported by the technicians of Shanghai BANNER Company and Shanghai Hiveson Office during the debugging, and expressed thanks.