Writing S-Functions

Process View

The following figures shows the order in which Simulink invokes an S-function's callback methods.

Calling Structure for the Real Time Workshop

When generating code, the Real-Time Workshop does not go through the entire calling sequence outlined above. After initializing the model as outlined in the preceding section, Simulink calls mdlRTW, an S-function routine unique to the Real-Time Workshop, mdlTerminate, and exits.

For more information about the Real-Time Workshop and how it interacts with S-functions, see The Real-Time Workshop User's Guide and The Target Language Compiler Reference Guide.

Alternate Calling Structure for External Mode

When running Simulink in external mode, the calling sequence for S-function routines changes. This picture shows the correct sequence for external mode.

Simulink calls mdlRTW once when it enters external mode and again each time a parameter changes or when you select Update Diagram under your model's Edit menu.

Note    Running Simulink in external mode requires the Real-Time Workshop. For more information about external mode, see the Real-Time Workshop User's Guide.

How Simulink Interacts with C S-Functions

Data View