Update a block's states
No
C, C++
#define MDL_UPDATE
void mdlUpdate(SimStruct *S, int_T tid)
S
SimStruct representing an S-Function block.
tid
Task ID.
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 does not have 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 its mdlUpdate
routine called
and it does not satisfy either of the above two conditions, specify that it has a discrete
state, using the ssSetNumDiscStates
macro in the
mdlInitializeSizes
function.
In C MEX S-functions, the tid
(task ID) argument specifies the task
running when the mdlOutputs
routine is invoked. You can use this argument
in the mdlUpdate
routine of a multirate S-Function block to encapsulate
task-specific blocks of code (see Multirate S-Function Blocks).
Use the UNUSED_ARG
macro if your C MEX S-function does not contain
task-specific blocks of code to indicate that the tid
input argument is
required but not used in the body of the callback. To do this, insert the line
UNUSED_ARG(tid)
after the declarations in mdlUpdate
.
Note
If you have Simulink
Coder™, when generating code for a noninlined C MEX S-function that contains this
method, make sure the method is not wrapped in a #if
defined(MATLAB_MEX_FILE)
statement. For example:
#define MDL_UPDATE #if defined(MDL_UPDATE) && defined(MATLAB_MEX_FILE) static void mdlUpdate(SimStruct *S, int_T tid) { /* Add mdlUpdate code here */ } #endif
The define
statement makes the mdlUpdate
method
available only to a MATLAB® MEX file. If the S-function is not inlined, Simulink
Coder cannot use this method, resulting in link or run-time errors.
For an example that uses this function to update discrete states, see dsfunc.c
. For an example
that uses this function to update the transfer function coefficients of a time-varying
continuous transfer function, see stvctf.c
.