Modbus Programming Recommendations

Read Register Recommendations

The registers of the IMU modules are available through Modbus communication in:

  • dataset registers (standard and/or legacy datasets)

  • device registers:

    • MicroLogic registers

    • IO module registers

    • IFM interface registers

    • IFE interface registers

To read the registers:

  • First read the registers that are available in datasets.

    • Standard dataset is recommended because it contains more data in a data format that allows a better accuracy.

    • Legacy dataset is used only for legacy equipments.

  • Then read the data that is not available in datasets in the device registers.

The benefit of datasets is that the most useful information of each IMU module is collected in one table that can be read with two or three read requests. Each module updates the values in the dataset registers on a regular basis.

The response time of requests to dataset registers is shorter than the response time of requests to device registers. Therefore, it is recommended to read the dataset registers instead of device registers, to improve the overall performance of the communication system.

Register Update

The values in the registers are updated in two different ways:

  • The measurement values are updated periodically, with a fixed refreshment rate.

  • The other values are updated when the value is changed.

Type of Registers

Register Update


Triggered by device replacement


Triggered by setting change


Periodically, with fixed refreshment rate

• Real-time measurements

Every 1 s

• Demand values of real-time measurements

Every 1 s

• Harmonic values

Every 3 s

• Energy measurements

Every 5 s

• Peak values of demand values of real-time measurements

Every 5 s

• Minimum and maximum values of real-time measurements

Every 5 s

Maintenance and diagnostic

Triggered by data change


Triggered by event detection

IO status

Triggered by status change

The refreshment rate of values is the same for the dataset registers and the device registers.

Use the refreshment rate to optimize the performance of the communication between the remote controller and the IMU modules.