Exporting a Modbus Address Map

A Modbus address map lists the Modbus addresses used by the EPM Modbus Server to exchange data with a remote Modbus client.

Note - You can only access this function if you have the Can access Communications Link permission. To update settings you must also have the Can edit Communication Link permission. If you need to access these functions and do not have permission, please contact your system administration.

When you add a Modbus Server comms link, no address map exists. The EPM Modbus Server creates the map automatically the first submit the application. The map includes:

  • All channel values, except Timers

  • Channel value status

  • Channel Alarm Active and Unacknowledged status

  • Batch State

  • Batch fields

  • Basic batch control commands

After the first submit, the EPM Modbus Server updates the existing address map. This minimize changes and helps preserve the remote client's configuration. When you submit changes:

  • Changes that do not affect channels or batch data, do not change the address map. For example, enabling the Web Server.

  • When you delete a channel or batch, its association with the Modbus address or addresses clears. The addresses usually remain in the map unless the resulting gap is too large. A remote client can read these addresses as zero, but cannot write to them.

  • When you add a channel or batch, new addresses are added at the end of the map.

  • When you change a channel or batch type, or change the Default Numeric Format or Default String Format parameters, the EPM Modbus Server checks each address. If the data type or register count changes, the updated line moves to the end of the map.

Note - Extensive channel or batch deletions or changes to the default data formats in the Modbus Server settings, can lead to fragmentation of the address map.

To remove the fragmentation, delete the address map and submit the change. The EPM Modbus Server then creates a new map. You must update the remote client's configuration to match the new map. See Deleting a Modbus Address Map for details.

Note - Adding, deleting, or editing channels, or changing the Modbus Server configuration, usually changes the address map. After you submit configuration changes, export the register map. Use the exported map to update the Modbus client configuration.

To export an address map:

  1. If you are exporting from an EPM Data Management device, insert a Universal Serial Bus Type-C (USB-C) flash drive into the right-hand side USB-C socket of your EPM Device:

    Tip - When exporting from a web browser, the file is saved in your PC’s Downloads folder. See Export File name, Understanding the Modbus server address Map for details.

  2. From EPM Device User Interface screen, select Options - Device I/O - Comms Link:

  3. The Comms Link screen displays:

    From the left-hand pane, select Options - Export Address Map:

    Tip - The Address map downloaded message displays briefly at the top right corner of the screen.
Note - When your address map is empty, the Register map empty message displays at the top right corner of the screen:

When you export a Modbus address map, EPM Data Management creates a comma-separated values(.csv) file with a structured file name.

The file name format is <IP address>_<Modbus comms link descriptor>_Address_Map.csv, where:

  • <IP address> is the IP address associated with the Modbus communication link.

  • '_' underscores are fixed parts of the file name.

  • <Modbus communication-link descriptor> is the Descriptor entered for the communication link.

  • _Address_Map.csv is fixed text.

Note - When you export the address map from an EPM device to a USB device, any characters in the communication link descriptor that are not printable ASCII characters display with underscores in the file name. For example, if the descriptor is Modbus 伺服器 1, the exported file name is: 10.10.0.2_Modbus _______1_Address_Map.csv.
Related topics - Comms Link, Configuring a Modbus Server, Deleting a Comms Link

Last update - October 2026