This error is due to an issue that was introduced in MATLAB R2020a with using Level-1 C MEX S-functions in conjunction with Rapid Accelerator Mode when continuous states are present. One of the following workarounds can be used to avoid this issue:
- Use a version of MATLAB prior to the R2020a release. If the Simulink model was produced using a later version of MATLAB, instructions for exporting the model to an earlier version can be found below:https://www.mathworks.com/help/releases/R2020a/simulink/ug/saving-a-model.html#f2-86382
- The second workaround would be to ensure that all C MEX S-functions used within the model are Level-2 S-functions. A guide on how to convert Level-1 S-functions to Level-2 can be found below: https://www.mathworks.com/help/releases/R2020a/simulink/sfg/converting-level-1-c-mex-s-functions-to-level-2.html
- The last workaround is to use Normal or Accelerator Mode as these modes are unaffected by the issue.
