Why do I get an error when using a referenced model in MATLAB R2014a?

When I try to simulate my system, I get the following error:

    The signal from 'test/Model' output port 1 is required to be persistent, hence this signal cannot be connected to a Merge block.

Why is this?

Answer 1

[MathWorks Support Team]

This is a known limitation in MATLAB R2014a.  

A Model block connected to a Merge block may incorrectly error out when the referenced model contains a Stateflow chart, Stateflow truth table, or Embedded MATLAB function block connected to a root Outport block.

You may receive an incorrect error message if your model meets all of the following conditions:

      1) The model is referenced in Normal mode.

      2) The model contains a Stateflow chart, a Stateflow truth table, or an Embedded MATLAB Function block that is directly connected to a root Outport block.

      3) The corresponding outport of the Model block is connected to a Merge block.

To avoid this error, insert a Signal Conversion block between the Stateflow chart, Stateflow truth table, or Embedded MATLAB Function block and the root Outport block.