I understand that you are using custom storage class and you are trying to generate the stubs automatically.This can be achieved as follows:
From the error I understood that, the header file path hasn't been added to the project file paths.
%To add a path to project.
addpath(<your-header-file-path>);
After adding it try SIL simulation again,since SIL can generate stubs for access functions automatically from Embedded Coder.
I hope this resolves the query.
Thanks and regards,
Venkat Siddarth V
