mdlStart and mdlTerminate Considerations
When you load a target application onto a target PC, the driver
executes the mdlStart callback
method. If the execution is successful, the driver then executes mdlTerminate.
If mdlStart does not
successfully complete, the application does not execute mdlTerminate. (Typically, mdlStart might not successfully complete
if the application cannot find a referenced I/O board or if the board
does not successfully initialize.)
When the target application does start, it executes mdlStart again, then repeatedly executes mdlOutputs. At the end of target application
execution, the application calls the mdlTerminate function.
With the above considerations, write mdlStart and mdlTerminate so that they cancel each
other out. Ensure that mdlTerminate deallocates
any resources that you allocated in mdlStart.
For example, if you set an output to high in mdlStart, reset it to the default level
in mdlTerminate. (Failure
to reset the output causes a high output before the application starts.)
As another example, if, in the mdlStart function, you allocate memory,
have mdlTerminate free the memory.
Although this description distinguishes between the driver initialization
and application start phases, you do not need to actually differentiate
between them. If you do need to do so, use the xpcIsModelInit function. This
function returns 1 while the model is initializing,
and 0 otherwise.
 | S-Function Guidelines | | DMA Considerations |  |
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