MATLAB: How to open the current Simulink models in previous versions of Simulink

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For example, I would like to know if my Simulink 3.0 models will load back into Simulink 2.2. When I try to bring models that were saved in Simulink 3.0 back into Simulink 2.2, I receive a number of warning messages, and then the model does not appear properly (blank). In some cases the model does not open at all.
An example of the warnings in Simulink 2.0:
 
Warning: Loading model 'modelname' generated with an earlier version (2.09) of SIMULINK.
Warning: vers.mdl, line 10: block_diagram does not have a parameter named 'PaperType'.
Warning: vers.mdl, line 11: block_diagram does not have a parameter named 'PaperUnits'.
Warning: vers.mdl, line 46: block_diagram does not have a parameter named 'SimulationMode'.
Warning: vers.mdl, line 49: block_diagram does not have a parameter named 'RTWRetainRTWFile'.
Warning: vers.mdl, line 53: block_diagram does not have a parameter named 'ExtModeMexFile'.
Warning: vers.mdl, line 54: block_diagram does not have a parameter named 'ExtModeBatchMode'.
Warning: vers.mdl, line 78: block_diagram does not have a parameter named 'LineDefaults'.
Warning: vers.mdl, line 79: block_diagram does not have a parameter named 'FontName'.
Warning: vers.mdl, line 80: block_diagram does not have a parameter named 'FontSize'.
Warning: vers.mdl, line 81: block_diagram does not have a parameter named 'FontWeight'.
Warning: vers.mdl, line 82: block_diagram does not have a parameter named 'FontAngle'.
When I try to bring a model from Simulink 2.2 to 2.1, I receive similiar warnings, but the model does appear.

Best Answer

As of Simulink 4.1 (R12.1), you can load newer Simulink models into an older version of Simulink.
To do this:
1. Open the newer Simulink model in the appropriate Simulink version
2. Save it as the required older version model by choosing the correct "Save as type" option through the File->Save-as menu or through File->Export Model to->Previous Version..., and then
3. Load the saved model in step 2 above in the selected older Simulink version.
For example, to load a Simulink 5.0 model into Simulink 3.0:
1. Open the model in Simulink 5.0
2. Save it as "Simulink 3.0/R 11Models (*.mdl)" by choosing the correct "Save as type" option through the File->Save-as menu, and then
3. Load the saved model in step 2 above in Simulink 3.0
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