MATLAB Answers


Does fixed point tool has any influence on MIL or SIL?

Asked by Yang Zhang on 9 Jul 2018
Latest activity Edited by Tabrez
on 13 Aug 2018 at 0:33

Dear Sir or Madam, I would like to learn something about fixed point tool just like the title from you. Does fixed point tool data type has any influence on MIL or SIL? If i use fixed point tool data type,whether the test case or test results has any different with the same model beside without useing fixed point tool data type? Another question,whether it is necessary to do SIL test if i do not use fixed point data type? Thank you.



Sign in to comment.

2 Answers

Answer by Rong Mi
on 8 Aug 2018 at 14:51

May I ask whether you are using Simulink Test product in your workflow? And which release are you using? Thank you.

  1 Comment

Sign in to comment.

Answer by Tabrez
on 9 Aug 2018 at 1:44
Edited by Tabrez
on 9 Aug 2018 at 5:55

Fixed point data types are less accurate (but fast in execution) alternative for floating point data types (single & double).

If you have a floating point model, then your calculation outputs in model will have real values with more accuracy. For example a signal PRESSURE can have value of 25.356568978.

If you convert same model to Fixed point, you need to scale each floating point signal to a fixed point type with required resolution.

Signals in your fixed point model will have accuracy based on scaling. For example PRESSURE can have value of 25.35, 25.40 etc (here resolution is 0.05)


If you test a floating point model and then convert it to Fixed point and test again, results will be different.


MIL test is used to check the correctness of logic/algorithm of your model.

SIL test used to check the correctness of generated code (there can be bug or issues with code generation process also)

So this is upto your project to decide which testings you need based on project complexity, model complexity, available tools etc.


Hi,Tabrez, Thanks for your reply,I know floating model has more accuracy,I have do some test and the result shows that there is no more difference between floating and fixed model except the accuracy of the output value. So I conclude fixed point tool has no influence on MIL or SIL.

Yes... a fixed point model only affect the accuracy (compare to floating point).

Also just as a note.. you will always need "Fixed Point Toolbox" to use fixed point model.

Sign in to comment.