Simulink xPC C-function static variable issues

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Istvan 2011-12-12

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   Hello,
I am trying to implement a Simulink model for xPC, in which I need to call a C function. This C function has some static variables, so that it remembers the value from the last step at the new step (from last call to current call). 
Now the problem:
It is one function. But I call it from TWO different Simulink S-function-creator blocks. I expected that two instances are created of this funcion's object, meaning the static variables in block 1 will not be mixed with those in block 2. But this is not the case. 
Could anyone please give me some advice how to isolate these instances? I.e. I what to have two instances of my C code running, so that static variables are NOT mixed. The two blocks must work competely separately.

(Note: I ask for 2 blocks here, but the issue is valid for N blocks too, so I cannot just rename my C function, as I would end up having many C functions doing the same thing).

*********************************

---- C function ---- ..... int b; static int a[100]; ....

called from (with different inputs, not shown here) -- S-function-builder block 1 -- AND -- S-function-builder block 2 -- ...

************************************

Thank you for any advice. Istvan

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Answer 1

Kaustubha Govind 2011-12-12

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I would recommend declaring D-Work vectors in your S-functions, and work with that memory from your C-function (ie. modify it to use a passed-in pointer which will be your DWork memory, rather than static variables).

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Istvan 2011-12-13

Thanks you for your answer.

Yes, I saw the D-Work vectors just about now, but I am not proficient in S-function writing, so I used the S-function-builder block. There, however, there is no way of using D-Work vectors...

Do you maybe nkow a good source of a --simple-- demo for a really minimalistic C S-function using D-Work vectors?

Thanks again -

Kaustubha Govind 2011-12-13

There's a lot of S-function demos in the documentation (type "sfundemos" to see them by classification). sfcndemo_sfunmem seems like a good beginner example.

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