This behavior is expected. When code is generated for the 'From file' block, the data in the target file is inlined to optimize it, i.e., hard-coded. Thus, any changes made to the target file after code generation are not honored by the compiled model.
For example, suppose you have a MAT-file containing a variable "A" with a value of 2, and a Simulink model that adds 1 to "A" and updates the MAT file.
- When the model is run in Simulink, it will read "A = 2", increment by 1, and save the updated "A" to the MAT file. Running the model afterward will continue to increment A by 1.
- Whereas, when the model is compiled, the value of "A = 2" is hard-coded, so the "From File" block reads the hard-coded value rather than reading from the file. Running the model afterward will continue to use hard-coded "A = 2" and increment it by 1.
For more limitations, please refer to the following documentation page by executing this command in the MATLAB R2020a command window:
>> web(fullfile(docroot, 'simulink/slref/fromfile.html?searchHighlight=fromfile'))
If you wish to change the data input to a compiled model after every run, please use an 'Import Block'. To view the relevant documentation, execute this command in the MATLAB R2020b command window:
>> web(fullfile(docroot, 'simulink/slref/inport.html'))
and supply the MAT-file as a root-level input. For more information, execute this command:
>> web(fullfile(docroot, 'simulink/ug/load-data-to-root-level-input-ports-1.html'))
This way, the code is compiled in such a way that the changing external data is honored.
Please follow the link below to search for the required information regarding the current release:
