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Execute Stateflow Chart Objects Through Scripts and Models

A standalone Stateflow® chart is a MATLAB® class that defines the behavior of a finite state machine. Standalone charts implement classic chart semantics with MATLAB as the action language. You can program the chart by using the full functionality of MATLAB, including those functions that are restricted for code generation in Simulink®. For more information, see Create Stateflow Charts for Execution as MATLAB Objects.

This example shows how to execute a standalone Stateflow chart by using a MATLAB script or a Simulink model.

Count Ways to Make Change for Currency

Open Chart

The file sf_change.sfx defines a standalone Stateflow chart that counts the number of ways to make change for a given amount of money. The chart contains these data objects:

  • x is the amount of money to change. The default value is 100.

  • coinValues is a vector of coin denominations arranged in increasing order. coinNames is an array of corresponding coin names. The default values represent standard American coins (pennies, nickels, dimes, and quarters).

  • tally is the number of valid change configurations.

  • tabula is an array containing the different valid change configurations.

  • chg, done, i, and n are local data used by the change-counting algorithm.

  • textWidth and quietMode are local data that control how the chart displays its results.

The chart begins with a potential change configuration consisting entirely of the lowest-value coins, specified by an index of 1. At each execution step, the state exchange modifies this configuration in one of two ways:

  • The substate move_up exchanges some lowest-value coins for a coin with a higher value, specified by the index i.

  • The substate move_down exchanges all of the coins with the value specified by the index i for lowest-value coins. Then move_up exchanges some lowest-value coins for a coin with a value specified by the index i+1 or higher.

A potential change configuration is valid when the number of cents represented by the lowest-value coins is divisible by the value of that type of coin. When the chart encounters a new valid configuration, it increments tally and appends the new configuration to tabula.

When no more coin exchanges are possible, the state stop becomes active. This state prints the results of the computation, transforms the contents of tabula to a table, and sets the value of done to true.

Execute Standalone Chart in a MATLAB Script

To run the change-counting algorithm to completion, you must execute the standalone chart multiple times. For example, the MATLAB script sf_change_script.m creates a chart object chartObj and initializes the value of the local data x to 27. The configuration option '-warningOnUninitializedData', which the script sets to false, eliminates the warning that tabula is an empty array in the new chart object. The while loop executes the chart until the local data done becomes true. Finally, the script displays the value of tabula.

chartObj = sf_change('-warningOnUninitializedData',false,x=27);

while ~chartObj.done
    step(chartObj);
end

disp(chartObj.tabula)
When you run this script, the standalone chart calculates the number of ways to make change for 27 cents by using standard American coins:
sf_change_script
.............
There are 13 ways to make change for 27 cents.
    Pennies    Nickels    Dimes    Quarters
    _______    _______    _____    ________

      27          0         0         0    
      22          1         0         0    
      17          2         0         0    
      12          3         0         0    
       7          4         0         0    
       2          5         0         0    
      17          0         1         0    
      12          1         1         0    
       7          2         1         0    
       2          3         1         0    
       7          0         2         0    
       2          1         2         0    
       2          0         0         1

To determine the number of ways to make change for a different amount, or to use a different system of currency, change the values of x and coinValues. For example, to use British currency, initialize coinValues to [1 2 5 10 20 25 50].

Execute Standalone Chart in a Simulink Model

This example uses:

Open Model

You can execute a standalone Stateflow chart from within a Simulink model. For example, the model sf_change_model contains two Stateflow charts that use the standalone chart sf_change to count the number of ways to make change for 27 cents in two different currency systems. You can simulate the model, but the functions that execute the standalone chart do not support code generation.

Each chart contains these states:

  • Initialize creates a local chart object chartObj that implements the change-counting algorithm for the input value x.

  • Execute calls the step function to execute the standalone chart and stores the result as the output data tally.

  • Finish displays the results of the algorithm in the Diagnostic Viewer window and sets the value of the output data done to true.

When both charts reach their respective Finish state, the simulation of the model stops and the Display blocks show the final values of the two tallies.

Execution Using MATLAB as the Action Language

The chart MATLAB syntax uses MATLAB as the action language. To execute the standalone Stateflow chart, this chart must follow these guidelines:

  • The local variable chartObj that contains the handle to the chart object has type Inherit: From definition in chart.

  • The Execute and Finish states access the local data for the standalone chart by calling the get function.

When you simulate this chart with an input of x = 27, the Display block Olde English shows a tally of 4. The Diagnostic Viewer window shows these results:

   Pennies    Shillings    Florins
   _______    _________    _______
     27           0           0
     15           1           0
      3           2           0
      3           0           1

Execution Using C as the Action Language

The chart C syntax uses C as the action language. To execute the standalone Stateflow chart, this chart must follow these guidelines:

  • The local variable chartObj that contains the handle to the chart object has type ml.

  • The Initialize state calls the ml function to create the chart object.

  • The Execute and Finish states use the ml namespace operator to access the step, get, and displ functions to execute the standalone chart, access its local data, and display the results of the algorithm.

For more information, see Access MATLAB Functions and Workspace Data in C Charts.

When you simulate this chart with an input of x = 27, the Display block Modern American shows a tally of 13. The Diagnostic Viewer window shows these results:

   Safety    FieldGoal    TouchDown
   ______    _________    _________
     12          1            0
      9          3            0
      6          5            0
      3          7            0
      0          9            0
     10          0            1
      7          2            1
      4          4            1
      1          6            1
      5          1            2
      2          3            2
      3          0            3
      0          2            3

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