Basic questions:

  • What is the fastest possible update time of values in e.g. WebVisu?
  • Is there a general empirical value for the update time of 'VISU_TASK'?
  • How does the system behave if the update time is set to 'only' 50 ms?
  • Are higher refresh time over 200ms useful to reduce system load?


Basically, the limiting values for the CODESYS visualization are always depends on the used system itself.

The standard update times of 150-200ms in the target settings (WebVisu, TargetVisu) under the 'Update rate', and 100ms in the task processing of the 'VISU_TASK':


Explanation of the 'Visu-Update Task' rates:

The interaction of the values is as follows:

                  The visible update rate (without inputs) = MAX (cycle time of the VISU-TASK + update rate of the target).

If the VISU-TASK runs fast enough and inputs are pending (e.g. mouse movements), there may be faster updates here.
The default settings (update rate of 200ms, VISU_TASK of 100ms) are a compromise resulting from the following considerations:

  • In the Codesys visualization, it is so that the VISU_TASK can run theoretically arbitrarily fast.
  • In fact, it is only calculated if there is a "request" of a client.
  • Corresponding requests arise on the one hand for cyclic updating of the visualization (redrawing of the visualization), or when inputs are executed in the visualization.
  • The rate at which cyclic updates occur is configured with this property for Target and WebVisu.
  • For cyclic updates, an update rate of 200ms is normally sufficient. With the double rate of the VISU_TASK a sufficiently fast reaction to inputs is usually also possible.
  • With the double rate of the VISU_TASK, a sufficiently fast reaction to inputs is usually also possible.

To the combination of 'Update rate' and 'VISU_TASK':

  • A (numerically) smaller update rate leads to a higher load of the controller because the visualization must be calculated more often.
  • A (numerically) smaller cycle time of the VISU_TASK allows a faster reaction to inputs.
    As long as no inputs are pending, the load on the system does not increase (if the update rate remains constant).

See also....