Why is my variable not staying updated in Simulink

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Hello,
I am using Simulink and have a variable set to zero in an enabled subsystem. I send the signal out of the subsystem and am trying to update it as x = x + 1 where x is the signal. After simulink goes through all the blocks once and gets back to where x = x + 1 the x is reset to 0. I have a breakpoint in the enabled subsystem where I initialized it and it never goes back there. Any ideas would be appreciated. Thank you!
  2 Comments
Kaustubha Govind
Kaustubha Govind on 18 Jun 2013
Could you please explain what block(s) you use to implement the x=x+1 part?
Nicholas
Nicholas on 18 Jun 2013
Edited: Nicholas on 18 Jun 2013
I am using MatLAB Function blocks. For a simplified example I am using a Matlab function block in the enabled subsystem that defines x = 0; Then I output the signal to the input of another MAtLAB function block outside of the subsystem where x = x + 1; I have a pulse generator for the enable of the subsystem

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Accepted Answer

Nicholas
Nicholas on 19 Jun 2013
Actually, I think I figured out what I needed to do. So I declared x as global and found the data store memory block. After I found the block I found http://www.mathworks.com/help/simulink/ug/using-global-data-with-the-matlab-function-block.html#bsdud7d-1 Thank you very much for your time and interest in helping me.

More Answers (1)

Erwin Torreao Dassen
Erwin Torreao Dassen on 18 Jun 2013
Edited: Erwin Torreao Dassen on 18 Jun 2013
Is this a custom matlab function block? In that case try declaring the variable persistent. (UPDATED)
  3 Comments
Erwin Torreao Dassen
Erwin Torreao Dassen on 19 Jun 2013
I'm not sure I understand what you trying to achieve. My guess of what is happening is that your matlab-function block that defines x = 0 is being used as input outside the subsystem. If that is the case the first block outside this subsytem will always receive 0 as input signal and it will never output more than 1... In fact, your matlab-function block is just a "constant" block.
What is the behavior you want to obtain?
Regards, Erwin
Nicholas
Nicholas on 19 Jun 2013
Thank you for your response. Yes my output is being used outside the subsystem as an input. So the overall goal is that I have a model where I want to measure a signal that goes to my MatLAB function block. Whenever the signal is zero and the simulation reaches that function block I want x to add one and be used as a counter. After the signal is zero for a certain amount of times through and the counter gets so high I want the output of my function block to change. I guess basically I'm not sure how to initialize a variable in simulink. Everytime Simulink's simulation reaches the end of all my blocks it wraps around and starts over again. So when I initialize the signal earlier on the simulation resets the value to 0 again. I thought I'd fixed the problem with the enabled subsystem block but apparently not. Thank you again.

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