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Configure Simplex Modbus TCP Communications

This guide describes how to configure the VIM to communicate with a simplex Modbus TCP device. This guide assumes a fictional Modbus device with the following registers available.

Modbus Slave Device Definition in VIMNet Explorer

  1. Select a serial port to create the field device placeholder.

    All devices on a port share retry, timeout, and transmit delay settings. Devices on a port are also enabled or disabled as a unit with the port enable flag in DeltaV. Devices should be grouped by port as the system architecture dictates.

    For the remainder of this guide, we will use Port 1 on Card 57.

  2. Right-click on the port and select Add Device.

    Figure 1 - Add Device Dialog

  3. Select the required Device Address (Figure 1).

    This address is used when addressing serial Modbus devices through an Modbus TCP to Modbus RTU serial device. In addition to that, some Modbus TCP devices will only respond to messages with the correct Modbus address in the message.

    The device address is also used to match the device in DeltaV to the device IP address assigned in VIMNet Explorer.

    For the remainder of this guide, the device address will be set to 1.

  4. Give the device an optional description (Figure 1).

    The description may be up to 32 characters long.

  5. Click on the Add button (Figure 1) to define the IP Address of the field device (Figure 2).

    Figure 2 - Define the Device Properties

  6. Select the desired Number of Simultaneous Messages (Figure 2).

    This parameter indicates the maximum number of messages the VIM will send before waiting for an acknowledgement. If you are unsure of the capacity of the field device, set this parameter to 1.

  7. Select the Modbus Protocol (Figure 2).

    If you are unsure of the protocol, select RTU TCP, as it is the most common. The RTU TCP protocol corresponds to the Modbus TCP/IP protocol (www.modbus.org). The other protocols are usually only used for Ethernet to serial bridge devices.

  8. Select the TCP Port (Figure 2) that the Modbus slave device is listening on for connections.

    If you are unsure of the port number, set it to 502, because that is the most common port number used.

  9. Click on OK to save the device definition. Beyond this point, the configuration is performed from DeltaV Explorer.

    Once all desired devices are configured in VIMNet Explorer, the next step is to send the configuration to the VIM. The procedure for this can be found in this guide: Upload Virtual IO Module Configuration. Once that is complete, the guide DeltaV Explorer Serial Dataset Configuration for Simplex VIM should be followed to finish the configuration.