Error "Undefined function or variable" when starting Simulink

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I'm currently using R2012b and get an error "Undefined function or variable 'delta_t'." when my function starts a Simulink Model (The Model was not made by me).
When I set a Breakpoint a this part of the function:
simout = sim(sim_pathfile,'SrcWorkspace','current');
I see the workspace of the function and there is a 1x1double variable called "delta_t" and the Base Workspace is empty. In this case I get the error "Undefined function or variable 'delta_t'."
If I define a variable "delta_t" in the Command Window before starting the function (so there is a variable "delta_t" in the Base Workspace), the Simulation starts and works fine. In this case, there are all the relevant variables in the function workspace and only the "delta_t" variable is in the function and the Base workspace.
So far it looks like the simulation uses the function workspace, as I defined it with:
And only for the delta_t variable it uses the Base workspace.
Now the part, where I stopped understanding anything:
I started to set the variable "delta_t" with various values in the function workspace (the variable "delta_t" in the Base workspace stays the same) when I looked at the results of the simulation, I saw that the simulation uses the value of the "delta_t" variable in the function workspace.
Could it be that the Simulink Model looks at the Base workspace if the variable "delta_t" is there (I do not understand why it does this only for this one variable and non of the others, it is using) and then uses the "delta_t" variable of the function workspace?
I hope it was understandable and I am not doing some really stupid mistake.
Thank you in advance
Walter Roberson
Walter Roberson on 6 Feb 2017
When you use a From Workspace block, then Simulink should look in the workspace of the function block that called sim() if the model was started that way, and would look in the base workspace if the model is started from a menu action or Function Key.

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