MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur télécharger pdf (Page 83)

Overview of the C MEX S-Function Routines

3-39

To check for a sample hit during execution (in mdlOutputs or mdlUpdate), use

the

ssIsSampleHit or ssIsContinuousTask macro. For example, if your first

sample time is continuous, then you used the following code fragment to check

for a sample hit. Note that you would get incorrect results if you used

ssIsSampleHit(S,0,tid).

if (ssIsContinuousTask(S,tid)) {

}

If, for example, you wanted to determine if the third (discrete) task has a hit,

then you would use the following code-fragment:

if (ssIsSampleHit(S,2,tid) {

}

The synopsis is:

static void mdlInitializeSampleTimes(SimStruct *S)

{

} /* End of mdlInitializeSampleTimes. */

Example: mdlInitializeSampleTimes.

This example specifies that there are two

discrete sample times with periods of 0.01 and 0.5 seconds.

static void mdlInitializeSampleTimes(SimStruct *S)

{

ssSetSampleTime(S, 0, 0.01);

ssSetOffsetTime(S, 0, 0.0);

ssSetSampleTime(S, 1, 0.5);

ssSetOffsetTime(S, 1, 0.0);

} /* End of mdlInitializeSampleTimes. */

Port-based Sample Times

The next three section discuss how to specify port-based sample times. You

must s pecify information in

•

mdlInitializeSizes

• mdlSetInputPortSampleTime

• mdlSetOutputPortSampleTime

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur Page 83