Writing S-Functions

Updating Run-Time Parameters

Whenever a user changes the values of an S-function's dialog parameters during a simulation run, Simulink invokes the S-function's mdlCheckParameters method to validate the changes. If the changes are valid, Simulink invokes the S-function's mdlProcessParameters method at the beginning of the next time step. This method should update the S-function's run-time parameters to reflect the changes in the dialog parameters.

Updating All Parameters at Once

If there is a one-to-one correspondence between the S-function's tunable dialog parameters and the run-time parameters, the S-function can use the SimStruct function ssUpdateAllTunableParamsAsRunTimeParams to accomplish this task. This function updates each run-time parameter to have the same value as the corresponding dialog parameter.

Updating Parameters Individually

If there is not a one-to-one correspondence between the S-function's dialog and run-time parameters or the run-time parameters are transformed versions of the dialog parameters, the mdlProcessParameters method must update each parameter individually.

If a run-time parameter and its corresponding dialog parameter differ only in value, the method can use ssUpdateRunTimeParamData to update the run-time parameter. This function updates the data field in the parameter's attributes record, ssParamRec, with a new value. If the run-time parameter and the dialog parameter differ only in value and data type, the method can use ssUpdateDlgParamAsRunTimeParam to update the run-time parameter. Otherwise, the mdlProcessParameters method must update the parameter's attributes record itself. To update the attributes record, the method should

1. Get a pointer to the parameter's attributes record, using ssGetRunTimeParamInfo.
2. Update the attributes record to reflect the changes in the corresponding dialog parameters.
3. Register the changes, using ssUpdateRunTimeParamInfo.

Run-Time Parameters

Tuning Runtime Parameters

© 1994-2005 The MathWorks, Inc.