Scope Output Delayed or Missing

During an external mode run, you notice either slow updates of Scope blocks or a complete failure to plot data in Scope blocks. This behavior could indicate that the real-time application sample time is near the lower threshold for your hardware.


The sample time is set in the Fixed step size (fundamental sample time) field in the Configuration Parameters Solver pane. The Fixed step size field appears only when Type is set to Fixed-step.

Plotting data has a lower priority than executing the application. A small sample time allows the application to run but can leave insufficient resources for plotting. If the sample time is so small that the application itself cannot run, an error message is displayed and real-time execution is terminated.

To check the sample time, select a larger sample time for your application. Change the sample time of any I/O drivers to be the same as the new application sample time, or to an integer multiple of that time. Then rebuild the model, connect to the target, and restart the real-time application.

As required, iterate changing the application sample time until scope output appears. For example, start with a sample time of 0.01 seconds, and confirm that your system runs and plots are displayed. Then decrease the sample time until you can both display scopes and meet your accuracy and response time requirements. Update the I/O driver sample time and rebuild the application after changing the application sample time.

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