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Component-Based Modeling with Model Reference

This example shows how to use Model Reference. It walks you through simulation and code generation of a model that references another model multiple times.

Example Requirements

During this example, Simulink® and Simulink® Coder™ generate code in the code generation folder created in the current working directory. If you do not want to (or cannot) generate files in this directory, you should change your working directory.

Simulink Coder is required to generate code to be deployed in standalone applications.

If you plan to alter the example models:

1. Preserve the example in its original state by copying the following files from your MATLAB® installation directory, without changing their names, to a different directory:

toolbox/simulink/simdemos/simfeatures/sldemo_mdlref_basic.slx
toolbox/simulink/simdemos/simfeatures/sldemo_mdlref_counter.slx

2. Change your current working directory to the directory to which you copied the files

3. Continue with the example

About Model Reference

Open the example model sldemo_mdlref_basicsldemo_mdlref_basic. This model contains three Model blocks: CounterA, CounterB and CounterC. These blocks reference the same model, sldemo_mdlref_counter, which is a separate model and not a subsystem of sldemo_mdlref_basic.

Simulation Mode

The Model block has a parameter named SimulationMode that controls how the referenced model is simulated. If the parameter is set to Accelerator, the referenced model is simulated through code generation. If the parameter is set to Normal, the referenced model is simulated in interpreted mode. In this model, the Model blocks CounterA and CounterB reference sldemo_mdlref_counter in Normal mode, which is indicated by the hollow corners on the Model block icon. The other instances, CounterC, references sldemo_mdlref_counter in Accelerator mode, which is indicated by the filled corners on the Model block icon. To learn more about interacting with models that are referenced more than once in Normal mode, see the example sldemo_mdlref_depgraph.

Figure 1: The top model, sldemo_mdlref_basic

Figure 2: The referenced model, sldemo_mdlref_counter

Model Reference has several advantages over subsystems:

  • You can develop the referenced model independently from the models in which it is used.

  • You can reference a model multiple times in another model without having to make redundant copies.

  • Multiple models can reference a single model.

  • The referenced model is not loaded until it is needed, a feature called Incremental Loading. Incremental loading speeds up model load times.

  • If a model is referenced in Accelerator mode, Simulink creates special binaries to be used in simulations. If the binaries are up-to-date, because the referenced model has not changed since the binaries were created, no code generation occurs when models that use these binaries are simulated or compiled. This is called Incremental Code Generation. The use of binaries increases simulation speed and modularity in code generation.

  • Generating code for a model with Model blocks also takes advantage of incremental code generation.

Simulation Through Code Generation (Does not require Simulink Coder)

Simulation of a model that references other models in Accelerator mode requires the generation of code and a binary file called the Simulation Target for each unique referenced model. This process does not require Simulink Coder. For this example, a simulation target is built for the sldemo_mdlref_counter model. You can create the Simulation Target by any of the following actions:

  • Updating sldemo_mdlref_basic

  • Simulating sldemo_mdlref_basic

  • Issuing the command:

slbuild('sldemo_mdlref_counter','ModelReferenceSimTarget')slbuild('sldemo_mdlref_counter','ModelReferenceSimTarget')

Remarks:

  • If a model is referenced in Normal mode, the simulation target is not built for that referenced model.

  • Once the simulation target is built, subsequently simulating or updating the model does not trigger a rebuild of the referenced model's simulation target unless the referenced model has changed.

  • Turn on the sample time colors for sldemo_mdlref_basic. Note that the Model blocks have inherited different sample times. The Model Blocks inherit their sample times if the referenced model does not explicitly specify a sample time.

Code Generation for Standalone Applications (Requires Simulink Coder)

When creating a standalone executable for sldemo_mdlref_basic, the code and binaries for the targets of sldemo_mdlref_counter are first generated. The necessary targets are built if they are not up-to-date. You can build the target for sldemo_mdlref_counter and the standalone executable for sldemo_mdlref_basic by any of the following actions:

  • Building the standalone executable for sldemo_mdlref_basic.

  • Building the Model Reference target of sldemo_mdlref_counter, followed by building the standalone executable for sldemo_mdlref_basic.

Remarks:

  • Once the model reference coder target of sldemo_mdlref_counter is built, subsequent builds of sldemo_mdlref_basic do not trigger a rebuild of sldemo_mdlref_counter unless sldemo_mdlref_counter changes (Incremental Code Generation).

  • Note that the code generated for the referenced model sldemo_mdlref_counter is reused.

  • The HTML report of the generated code for sldemo_mdlref_basic has a link to the HTML report of the generated code for sldemo_mdlref_counter in the Referenced Model section.

Build the Standalone Target and view the HTML report of the generated codeBuild the Standalone Target and view the HTML report of the generated code

Incremental Loading

Close sldemo_mdlref_counter and sldemo_mdlref_basic and then re-open sldemo_mdlref_basicre-open sldemo_mdlref_basic. At the MATLAB prompt issue the command:

find_system('type','block_diagram')

The referenced model is not listed because it is not loaded. Right click on any Model block and select Open. At the MATLAB prompt, issue the command:

find_system('type','block_diagram')

The referenced model is now listed, illustrating how incremental loading works.

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