Stateflow User's Guide

Creating a Function

You create a Stateflow graphical, truth table, or embedded MATLAB function in Stateflow diagrams with the following steps:

1. Select a drawing tool for the function from the Stateflow drawing toolbar as follows:
   
   

   Tool	Function
   	Graphical
   	Truth Table
   	Embedded MATLAB

2. Move the cursor to the location for the new function and click to place it.

1. The new function appears as an unnamed object in the Stateflow diagram editor with a flashing text cursor as seen in the following graphical function example.

   

   The new function also appears in the Model Explorer as a child of the chart or state in which it is drawn. In the following example, a graphical function is added to its parent Stateflow chart, myChart.

   

• A function can reside anywhere in a chart, state, or subchart. The location of a function determines its scope, that is, the set of states and transitions that can call the function. In particular, functions are visible to the chart, to the parent state and its parents, and to sibling transitions and states with the following exceptions.

  • If the chart containing the function exports its graphical functions, the scope of the function is the entire Stateflow machine, which encompasses all the charts in the model. See Exporting Functions for more information.
  • A function defined in a state or subchart overrides any functions of the same name defined in the parents and ancestors of that state or subchart.

3. Enter the function signature and click outside of the function box.

1. The function signature specifies a name for the function and formal names for its arguments and return value. A signature has the following syntax:

   • r = func(a1,a2,...an)
     

• where func is the function's name, a1, a2, an are formal names for its arguments, and r is the formal name for its return value (only one return is allowed). Arguments and return values can be scalars, vectors, or 2-dimensional matrices of any type. Matrices with a row or column dimension of 1 are treated as row or column vectors, respectively.

1. The following example shows a signature for a graphical function named f1 that takes two arguments, a and b, and returns a value y.

   

   Notice that the function box in the preceding example has been enlarged to accomodate the width of its label signature. You enlarge function boxes in their corners, just as for state and box objects.

   The signature for a function appears as a property of its owning object in the Model Explorer.

   

   If you expand the parent object in the Model Explorer, you can see the return values and arguments that you declare in the signature for a function as data items parented by the function.

   

   The Scope field in the Explorer indicates the role of each argument or return value. Arguments have the scope Function input, and return values have scope Function output.

Note    You can use the Stateflow diagram editor to change the signature of a graphical function at any time. When you are done editing the signature, Stateflow updates the data dictionary and the Model Explorer to reflect the changes.

Using Functions to Extend Actions

Programming Functions

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