MODBUS RTU is a layer 2 network protocol created in the end of the 70’s with the necessity of a fieldbus protocol in industry to transmit and receive data in a simple way through the many devices of a network, in mind. MODBUS RTU uses RS-485 electrical standards and works on a Master-Slave setup, where a master writes and reads data into the registers of the slaves in the network. It has become the default protocol in many industry devices like PLCs, drives, sensors and it is highly used nowadays.
The Delta C2000 also uses MODBUS RTU as a built-in communication protocol. In this application note we are going to learn how to set up a Master – slave configuration, write, read and program the internal PLC with ISPsoft to work on a peer-to-peer (P2P) application with 2 motors, one used as a master and other as a slave. P2P is used when we want both motors to run at the same speed together in an application and monitor their current, its typical use can be applied to pumps, fans, conveyors, rollers. It can be also taken as an alternative for the analog input/output of the drive, when we need more than just 2 measurements. Delta C2000 also permits to create a small Text panel customized display with TPEditor, which we will follow at the end of the chapters.
This week we would like to show you two new function blocks (FB) that we have developed to make even easier to use Delta Industrial Automation products.
Usually we need to control several AC drives from a single Master PLC and Modbus communication is a cheap and helpful way to get it.
In order to reduce programming and commissioning time we have developed two FB:
COM2_VFDLINK: Configures the communication parameters (baudrate, number of bits, parity,…) that all the nodes on the network have to share and informs about the communication state of each node.
DELTA_VFD: Controls each one of the slaves VFD, we can Start/Stop, Forward/Reverse, frequency command and reset faults. On the other side, the FB informs us about the status of the drive, alarm code, output frequency and output current.
Below you’ll find the FB library ready to be imported in your ISPSoft and a little pdf explaining the I/O of each FB, enjoy it!
DVP12-SE PLC can be configured to exchange data between other PLCs via Ethernet(modbus TCP/IP) by using DCISoft Software. DCISoft Software is an integrated configuration tool of Delta network modules for WINDOWS operation system. Below is how to configure DVP12-SE for Data Exchange with other PLCs.
Ethernet function of DVP12-SE PLC
Follow the steps below to configure DVP12-SE for Data Exchange.
1. Communication Setting: Start DCISoft in your PC, and click Communication Setting on the Tools menu.
When the DCISoft opens as shown above,Click the communication settings icon on the tool menu as shown below. Set the communication type and the communication parameter that you prefer to use on your PC for connecting the DCISoft with the DVP12-SE PLC .
2. Auto Search
After setting the communication type and communication parameter, then push the “Auto Search” button to search for the DVP12-SE in the DCISoft for configuration.
3. Setup Overview : after the step above, the interface below will appear. Double-click on the DVP12-SE module icon contained in the interface below to enter the setup overview page.
After the step above, the interface below will appear which contains several tabs in the tool bar. The first tab is the overview tab, this tab shows the current basic status of the DVP12-SE PLC module. I will further talk about theBasicand theData Exchangetabs used for the configuration of the DVP12-SE PLC.
5. Basic settings
Push the basic tab, the interface below for setting the network parameter will appear.
5.1 Module name: There can be many DVP12-SE on the network. Thus, you can set up a module name for each module to identify the module when you need to use them.
5.2 Network setup: In the IP configuration field, you can Enable DHCP (DHCP: is Automatically updated by the server. There has to be a server in the LAN) or static IP. (Static IP: Is Preset or manually modified by the user). if you choose Static IP, manually modified the; IP address, Subnet mask(Netmask ) and the Gateway IP.
6. Data Exchange
Click the data exchange tab, the interface below will appear. The Data Exchange is used for configuring exchange of data between PLC via network. A Delta Ethernet master can read/write data from/into a slave.
If a device which is not a Delta PLC is connected, users can use the hexadecimal four-digit MODBUS address of the device for data exchange.
6.1. Enable data Exchange:
Users can enable or disable a data exchange. After a data exchange is enabled, the data will
6.2 .Enable Condition:
In theenable condition field,you can select Always Enable,Program Control or PLC Run. If Always Enable is selected,DVP12-SE will execute data exchange continuously until the setting in DCISoft is changed.
If Program Control is selected, DVP12-SE will execute data exchange according to the
program setting. If PLC Run is selected, DVP12-SE will execute data exchange when the DVP12-SE Run Mode switch is activated
6.3. Slave ID, IP Address and Enable (Station Address-IP Address:)
You have to type in the IP address of the slaves. for example, If the IP address of a slave is 192.168.0.1, and the station number of the slave is 1, you can type 1 in the first Slave ID cell, select the box in the first Enable cell, and type in the first IP Address cell. You have to enable and include the IP addresses of the other PLC that will be slaves
6.4. Master Device, Slave Device, and Quantity:
below is a brief information about the function of Master Device, Slave Device, and Quantity in data exchange dialog box of DCISoft.
In the Master Device, Slave Device cell, if the the slaves device is a Delta PLC, enter the starting D register that you will use for data exchange.
If the slave is a third party device(not a delta PLC), enter the an hexadecimal four-digit MODBUS address that the device will use for data exchange. see below the meaning of the arrow signs in the master device and slave device column of data exchange page in DCISoft.
Reading (←): Initial reception register in a master← Initial transmission register in a slave
Writing (→): Initial transmission register in a master→ Initial reception register in a slave
6.5. Quantity: A slave station can send 100 pieces of data at most and receive 100 pieces of data at most Simultaneously
See explanation below on how the Quantity field of data exchange works.
From the figure above, with the quantity specified as 100, see explanation below what the specified D registers does.
writing data from the slave side and receiving data at the master side (← )
Looking at the first row of the Master Device and Slave Devicecolumn as contained in the figure above, The master will use D register ; D0, D1……….up to D99 (that is possible 100 pieces of different data base on the “100” Quantity Specified in DCISoft) to receive the data written by D99, D100…..up to D199 of the slave simultaneously. (that is possible 100 pieces of different data base on the “100 ” Quantity Specified in DCISoft)
writing data from the master side and receiving data at the slave side (→)
Looking at the second row of the Master Device and Slave Devicecolumn as contained in the figure above, The master can write data to the slave D register using D200, D201……up to D300 and the slave can read this data using D300, D301…D400.
From the configuration above, I can send and receive up to 100 pieces of different data by enabling data exchange and specifying a quantity of 100.
To save your configuration to your PC desktop or USB stick, push the new button as show above and save the DCISoft file
Look at the video below to see how I send and receive data between two DVP12-SE using the configuration that I explained earlier above, I use one DVP12-SE PLC as a master and the other DVP12-SE PLC as a slave for data exchange.