Required

No

语言

C, C++

Arguments

Description

The Simulink^®engine invokes this optional method at each major simulation time step. The method should compute the S-function's states at the current time step and store the states in the S-function's state vector. The method can also perform any other tasks that the S-function needs to perform at each major time step.

Use this code if your S-function has one or more discrete states or doesnothave direct feedthrough.

The reason for this is that most S-functions that do not have discrete states but do have direct feedthrough do not have update functions. Therefore, the engine is able to eliminate the need for the extra call in these circumstances.

If your C MEX S-function needs to have itsmdlUpdateroutine called and it does not satisfy either of the above two conditions, specify that it has a discrete state, using thessSetNumDiscStatesmacro in themdlInitializeSizesfunction.

In C MEX S-functions, thetid(task ID) argument specifies the task running when themdlOutputsroutine is invoked. You can use this argument in themdlUpdateroutine of a multirate S-Function block to encapsulate task-specific blocks of code (seeMultirate S-Function Blocks).

Use theUNUSED_ARGmacro if your C MEX S-function does not contain task-specific blocks of code to indicate that thetidinput argument is required but not used in the body of the callback. To do this, insert the line

UNUSED_ARG(tid)

after the declarations inmdlUpdate.

#define MDL_UPDATE #if defined(MDL_UPDATE) && defined(MATLAB_MEX_FILE) static void mdlUpdate(SimStruct *S, int_T tid) { /* Add mdlUpdate code here */ } #endif

Example

For an example that uses this function to update discrete states, seedsfunc.c. For an example that uses this function to update the transfer function coefficients of a time-varying continuous transfer function, seestvctf.c.

See Also

mdlDerivatives,ssGetContStates,ssGetDiscStates,Update