Why do I get a java.lang.NullPointerException error when I change the width of my Altera DSP Builder Input block in Simulink?

You will receive an error message similar to the one below when changing the parameters of certain Altera® DSP Builder blocks, including the Input block, if the Simulink® model is using the .SLX format - <filename>.slx.

Error reported by S-function 'sInOut' in <model_name>/Input':
java.lang.NullPointerException at
com.altera.dspbuilder.simulation.Model.getAbsoluteTestbenchPath(Unknown
Source) at come.altera.dspbuilder.simulation.Model.getValidIOFile....

To workaround this issue save the Simulink model as an MDL format model - <filename>.mdl.  At this point you should be able to make the parameter changes without the error.

This issue will be fixed in a future release of the DSP Builder / Quartus® II software.