Real-Time Workshop Embedded Coder

Basic Code Generation Options

To access the basic code generation options, select the Real-Time Workshop tab of the Simulation Parameters dialog box. Then select ERT code generation options (1) from the Category menu.

Figure 3-1 displays the basic code generation options (with default settings) for the Real-Time Workshop Embedded Coder.

Figure 3-1: Basic Code Generation Options

Setting the basic code generation options as follows will result in more highly optimized code:

• Consider clearing the Initialize internal data and Initialize external I/O data options.

• These options (both on by default) control whether internal data (block states and block outputs) and external data (root inports and outports whose value is zero) are initialized. Initializing the internal and external data whose value is zero is a precaution and may not be necessary for your application. Many embedded application environments initialize all RAM to zero at startup, making Initialize internal data redundant.

  However, be aware that if Initialize internal data is turned off, it is not guaranteed that memory will be in a known state each time the generated code begins execution. If you turn the option off, running a model (or a generated S-function) multiple times can result in different answers for each run.

  This behavior is sometimes desirable. For example, you can turn off Initialize internal data if you want to test the behavior of your design during a warm boot (i.e., a restart without full system reinitializiation).

  In cases where you have turned off Initialize internal data but still want to get the same answer on every run from a Real-Time Workshop Embedded Coder generated S-function, you can use either of the following MATLAB commands before each run:

  • clear <SFcnName> (where SFcnName is the name of the S-function)
    

  or

  • clear mex
    

  A related option, Initialize floats and doubles to 0.0, lets you control the representation of zero used during initialization. See Initialize Floats and Doubles to 0.0.

  Note that the code still initializes data structures whose value is not zero when Initialize internal data and Initialize external I/O data are selected.

  Note also that data of ImportedExtern or ImportedExternPointer storage classes is never initialized, regardless of the settings of these options.

• Clear the Terminate function required option if you do not require a terminate function for your model.
• Select the Single output/update function check box. Combining the output and update functions is the default. This option generates the model_step call, which reduces overhead and allows Real-Time Workshop to use more local variables in the step function of the model.
• If your application uses only integer arithmetic, select the Integer code only option to ensure that generated code contains no floating-point data or operations. When this option is selected, an error is raised if any noninteger data or expressions are encountered during code generation. The error message reports the offending blocks and parameters.
• Clear the MAT-file logging option. This setting is the default, and is recommended for embedded applications because it eliminates the extra code and memory usage required to initialize, update, and clean up logging variables. In addition to these efficiencies, clearing the MAT-file logging option has the following effects:
• Under certain conditions, code and storage associated with root output ports are eliminated, achieving further efficiency. See Virtualized Output Ports Optimization for information.
• The model_step function does not check the current time against the stop time. Therefore the generated program runs indefinitely, regardless of the setting of the model's stop time. The ert_main program displays a message notifying the user that the program will run indefinitely.

Controlling and Optimizing the Generated Code

Virtualized Output Ports Optimization