MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur télécharger pdf (Page 82)

3 Writing S-Functions As C-MEX files

3-38

Alternatively, you can specify that the sample time is in herited from the

driving block in which case the S-function can have only one sample time pair:

[INHERITED_SAMPLE_TIME, 0.0 ]

[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET]

The following guidelines may help aid in specifying sample times:

• A continuous function that changes during m inor integration steps should

[CONTINUOUS_SAMPLE_TIME, 0.0] sample time.

• A continuous function that does not change during minor integration steps

should register the

[CONTINUOUS_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.

• A discrete function that changes at a specified rate should register the

discrete sample time pair

[discrete_sample_period, offset]

where

discrete_sample_period > 0.0

and

0.0 <= offset < discrete_sample_period

• A discrete function that changes at a variable rate should register the

variable step discrete

[VARIABLE_SAMPLE_TIME, 0.0] sample time. The

mdlGetTimeOfNextVarHit function is called to g et the time of the next

sample hi t for the variable step discrete task. The

VARIABLE_SAMPLE_TIME

can be used with variable step solvers only.

If your function has no intrinsic sample time, then you must indicate that it is

inherited according to the following guidelines:

• A function that changes as its input changes, even during minor integration

steps, should register the

[INHERITED_SAMPLE_TIME, 0.0] sample time.

• A function that changes as its input changes, but doesn't change during

minorintegrationsteps(thatis,heldduring minor steps),shouldregisterthe

[INHERITED_SAMPLE_TIME, FIXED_IN_MINOR_STEP_OFFSET] sample time.

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MATLAB SIMULINK 7 - DEVELOPING S-FUNCTIONS Guide de l'utilisateur Page 82