The meter as Modbus master

ION8650 meters can act as a Modbus master using the Modbus RTU and Modbus/TCP protocols:

  • The meter can Modbus master using Modbus RTU over serial connections between the meter’s COM1 or COM4 ports and the Modbus slave devices. It can Modbus master over both COM1 and COM4 simultaneously.
  • Meters with an Ethernet connection can Modbus master over TCP/IP using up to ten available TCP connections. These TCP connections are dedicated to Modbus mastering, and are not included in the maximum of eight (8) Ethernet connections.

The meter acting as Modbus master can write data to (export) and read data from (import) Modbus slave devices. The data can be processed by the meter and sent out using other communications methods (email, Power Monitoring Expert, etc.). The meter can also send data directly to other devices on a Modbus network.

NOTE: Modbus master functionality is not available on the ION8650C.

For more information on Modbus mastering, see the Modbus and ION Technology technical note.

NOTE: If you encounter issues reading or writing to the device using Modbus, ensure that your device’s security settings allow Modbus programming. See Cybersecurity for more information on device security.

Configuring the meter as a Modbus master

This section describes the ION modules involved in using the meter as a Modbus master and using ION Setup or Power Monitoring Expert.

The Modbus master configuration

There is no preconfigured Modbus master framework on your meter. This functionality must be enabled by configuring the following modules in your meter’s framework.

Modbus master ION modules

Several ION modules work together to create Modbus master functionality on the meter. Your meter has some or all of these modules, depending on the model and firmware version. See the ION Reference for more information on these and other ION modules:

  • Modbus Master Device module: reads data from a Modbus slave, which can be an ION meter or third-party device. This imported data can be used by other ION modules. The Modbus Master Device module references a Modbus Master Map module setup register to specify the Modbus format, scaling, and base address settings.
  • Modbus Master Map module: provides a common place to hold setup information (used to decode a Modbus response) for specific device types. This information can be referenced by multiple Modbus Master Device modules.
  • Modbus Master Options module: maps any serial connection or Ethernet TCP socket from the Modbus Import, Modbus Export and Modbus Master Device modules to any serial communications port or unique IP address and port number.
  • Modbus Export module: provides write functionality.
  • Modbus Import module: provides read functionality. This data can then be used by other ION modules.

NOTE: Modbus Export and Modbus Import modules are legacy modules and are provided for backwards compatibility.

See the Modbus and ION Technology technical note for more information on configuring Modbus master and ION Reference for more information on the modules used in Modbus mastering.

Using the front panel

You cannot configure Modbus through the meter’s front panel. You can only assign the Modbus protocol to communication ports. See Communications for details.

Use Power Monitoring Expert or ION Setup to perform full Modbus configuration.

Using ION Setup

  1. Open the Setup Assistant for your meter. See the ION Setup Help for instructions.
  2. Select Communications > 3rd Party Protocols.
  3. Click on the Modbus Master tab.
  4. Click Add to add a Modbus slave device. The Modbus Device dialog box appears.
  5. Type the slave device’s name and a label suffix (if applicable). Select the device type of the slave device from the Device Type list (in this example, an ION6200).
  6. Type the unit ID of the slave device in the Slave ID box.
  7. Select the serial or TCP connection you want to configure from the Connected via list. This is the connection used by the Modbus master to connect to that slave device. Click Connections. The Modbus Device dialog box appears.
  8. Select the tab that corresponds to the connection you are configuring (for example, if you selected TCP Connection 1 from the Connected via list, select the TCP 1 tab), and edit the text boxes as follows:
    • Serial Connections: Select the port that is connected to the Modbus slave devices from the Assigned Port dropdown list.
    • TCP Connections: Type the IP address of the Modbus slave device. Ensure that the IP port is 502. You can enter up to ten (10) Modbus slave device IP addresses.

      NOTE: For Modbus mastering over RTU, the total number of possible serial connections is limited by the number of physical serial ports on the meter that can Modbus master. The meter has two physical serial ports that support Modbus master (COM1 and COM4).

      To Modbus master over Ethernet, the meter must have the optional Ethernet connection.

      Click OK when you have finished configuring connections to return to the Modbus Device dialog box.

  9. Click OK to add the slave device. The device now appears in the list. Continue adding devices by clicking Add until all devices are entered.

NOTE: The meter as Modbus master over TCP/IP will attempt to communicate to a slave for up to 100 seconds (as per the RFC1122 standard) before moving on to the next slave device.

See the Modbus and ION Technology technical note for more information.

Using Power Monitoring Expert

Use Designer to configure Modbus master functionality on your meter.

  1. Open the master meter in Designer.
  1. Navigate to the Modbus Master Options module. Right-click on the center of the module icon to access the ION Module Setup dialog box.
  2. Configure the setup registers by selecting the setup register you want to change and clicking Modify, or by double-clicking on the register.
    • Serial Connections: Select the appropriate port from the dropdown list.
    • TCP Connections: Enter the IP address of the Modbus slave device, followed by a colon (:) and the IP port (502), for example, 192.168.0.1:502. You can enter up to 10 unique IP addresses.

      NOTE: For Modbus mastering over RTU, the total number of possible serial connections is limited by the number of physical serial ports on the meter that can Modbus master. The meter has two physical serial ports that support Modbus master (COM1 and COM4).

      To Modbus master over Ethernet, the meter must have the optional Ethernet connection.

  3. Create a new Modbus Master Map module for each slave device. The Modbus Master Map module has two setup registers:
    • Device Type: Enter the type of device that you want to map. This value is referenced by the Modbus Master Device module.
    • Device Map: This is the data that you want to access from the Modbus slave device, in the form of text strings containing the parameter label, register value, data format, etc.
  4. Create a new Modbus Master Device module for each slave device. Configure the following setup registers in the Modbus Master Device module:
    • Connection: Select the serial or TCP connection being used to communicate with the slave device.
    • Slave Addr: Type the unit ID of the slave device.
    • Device type: Type a device type string. Ensure that this is the same as the device type entered in the Modbus Master Map module.
    • Slave name: Type a name for the slave device.
  5. Link the module inputs and outputs as required.
  6. Select File > Send & Save when you are finished.

    7. See Power Monitoring Expert help for more information on creating, modifying and linking modules in Designer and the ION Reference for details of module setup and output registers.