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Writing S-Functions That Support Code Reuse

The Real-Time Workshop code reuse feature generates code for a subsystem in the form of a single function that is invoked wherever the subsystem occurs in the model (see Creating Subsystems). If a subsystem contains S-functions, the S-functions must be compatible with the code reuse feature. Otherwise, the code generator might not generate reusable code from the subsystem or might generate incorrect code.

If you want your S-function to support the subsystem code reuse feature, you must ensure that the S-function meets the following requirements:

• The S-function must be inlined.

• Code generated from the S-function must not use static variables.

• The S-function must initialize its pointer work vector in mdlStart and not before.

• The S-function must not be a sink that logs data to the workspace.

• The S-function must register its parameters as run-time parameters in mdlSetWorkWidths. (It must not use ssWriteRTWParameters in its mdlRTW function for this purpose.)

• The S-function must not be a device driver.

In addition to meeting the preceding requirements, your S-function must set the SS_OPTION_WORKS_WITH_CODE_REUSE flag (see the description of ssSetOptions in the Simulink Writing S-Function documentation). This flag assures the code generator that your S-function meets the requirements for subsystem code reuse.

Writing S-Functions That Specify Sample Time Inheritance Rules

Writing S-Functions for Multirate Multitasking Environments

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