How Stateflow Software Generates Content for Truth Tables

On this page…
Types of Generated Content Viewing Generated Content How Stateflow Software Generates Graphical Functions for Truth Tables How Stateflow Software Generates MATLAB Code for Truth Tables

Types of Generated Content

Stateflow software realizes the logical behavior specified in a truth table by generating content as follows:

Type of Truth Table	Generated Content
Stateflow Classic	Graphical function
MATLAB	MATLAB code

Back to Top

Viewing Generated Content

You generate content for a truth table when you simulate your model. Content regenerates whenever a truth table changes. To view the generated content of a truth table, follow these steps:

1. Simulate the model that contains the truth table.

2. Double-click the truth table to open its editor.

3. Click the View Generated Content button:

   

Back to Top

How Stateflow Software Generates Graphical Functions for Truth Tables

This section describes how Stateflow software translates the logic of a Stateflow Classic truth table into a graphical function.

In the following example, a Stateflow Classic truth table has three conditions, four decisions and actions, and initial and final actions.

Stateflow software generates a graphical function for the preceding truth table. The top half of the flow graph looks like this:

The top half of the flow graph executes as follows:

• Performs initial actions

• Evaluates the conditions and stores the results in temporary data variables

  The temporary data for storing conditions is based on the labels that you enter for the conditions. If you do not specify the labels, temporary data variables appear.

The bottom half of the flow graph looks like this:

In the bottom half of the flow graph, the stored values for conditions determine which decision is true and what action to perform. Each decision appears as a fork from a connective junction with one of two possible paths:

• A transition segment with a decision followed by a segment with the consequent action

  The action appears as a condition action that leads to the FINAL action and termination of the flow graph.

• A transition segment that flows to the next fork for an evaluation of the next decision

  This transition segment has no condition or action.

This implementation continues from the first decision through the remaining decisions in left-to-right column order. When a decision match occurs, the action for that decision executes as a condition action of its transition segment. After the action executes, the flow graph performs the final action for the truth table and terminates. Therefore, only one action results from a call to a truth table graphical function. This behavior also means that no data dependencies are possible between different decisions.

Back to Top

How Stateflow Software Generates MATLAB Code for Truth Tables

Stateflow software generates the content of MATLAB truth tables as MATLAB code that represents each action as a nested function inside the main truth table function.

Nested functions offer these advantages over subfunctions:

• Nested functions are independent of one another. Variables are local to each function and not subject to naming conflicts.

• Nested functions can access all data from the main truth table function.

The generated content appears in the function editor, which provides tools for simulation and debugging.

Here is the generated content for the MATLAB truth table described in Programming Actions in MATLAB Action Language:

• Main truth table function

  function t = ttable(x,y,z)
  
  % Initialize condition vars to logical scalar
  XEQ1 = false;
  YEQ1 = false;
  ZEQ1 = false;
  
  % Condition #1, "XEQ1"
  % x is equal to 1
  XEQ1 = logical(x == 1);
  
  % Condition #2, "YEQ1"
  % y is equal to 1
  YEQ1 = logical(y == 1);
  
  % Condition #3, "ZEQ1"
  % z is equal to 1
  ZEQ1 = logical(z == 1);
  
  if (XEQ1 && ~YEQ1 && ~ZEQ1) % D1
      A1();
  elseif (~XEQ1 && YEQ1 && ~ZEQ1) % D2
      A2();
  elseif (~XEQ1 && ~YEQ1 && ZEQ1) % D3
      A3();
  else % Default
      A4();
  end

• Action A1

  function A1()
  % Action #1, "A1"
  % Maintain a counter and a circular vector of length 6.
  % Every time this action is called,
  % output t takes the next value of the vector.
  
  persistent values counter;
  cycle = 6;
  
  if isempty(counter)
    % Initialize counter to be zero
    counter = 0;
  else
    % Otherwise, increment counter
    counter = counter + 1;
  end
  
  if isempty(values)
    % Values is a vector of 1 to cycle
    values = zeros(1, cycle);
    for i = 1:cycle
      values(i) = i;
    end
  
    % For debugging purposes, call the MATLAB
    %  function "plot" to show values
    plot(values);
  end
  
  % Output t takes the next value in values vector
  t = values( mod(counter, cycle) + 1);

• Actions A2, A3, and A4

  function A2()
  % Action #2, "A2"
  % set t to 2
  
  t=2;
  
  %==================================
  function A3()
  % Action #3, "A3"
  % set t to 3
  
  t=3;
  
  %==================================
  function A4()
  % Action #4, "A4"
  % set t to 4
  
  t=4;

Back to Top

Correcting Overspecified and Underspecified Truth Tables

Truth Table Editor Operations

© 1984-2012- The MathWorks, Inc.    -   Site Help   -   Patents   -   Trademarks   -   Privacy Policy   -   Preventing Piracy   -   RSS