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TLC Files

TLC Program

Target Language Compiler (TLC) works with the Simulink® software to generate code.

A TLC program is a collection of ASCII files called scripts. Because TLC is an interpreted language, there are no object files. The single target file that calls (with the %include directive) other target files used for the program is called the entry point.

Available Target Files

TLC interprets the set of target files to transform the partial representation of the Simulink model (model.rtw) into target-specific code.

Target files provide you with the flexibility to customize the code generated by the compiler. For example, if you use the available system target files, you produce generic C or C++ code from your Simulink model. This executable code is not platform-specific.


Do not customize TLC files even though the capability exists to do so. Such TLC customizations might not be applied during the code generation process and can lead to unpredictable results. Customize only the TLC files that you create.

The parameters in the target files are read from the model.rtw file and looked up by using block scoping rules. You can define additional parameters within the target files by using the %assign statement.

Use target language directives to write target files. Target Language Compiler Directives provide complete descriptions of the block scope rules and the target language directives.

model.rtw File and Scopes describes model.rtw file, which is useful for creating and modifying target files.

In the context of code generation, there are two types of target files:

  • System target files

    System target files determine the overall framework of code generation. They determine when blocks are executed, how data is logged, and so on.

  • Block target files

    Each block has a target file that determines what code should be generated for the block. The code can vary depending on the exact parameters of the block or the types of connections to it (e.g., wide vs. scalar input). For more information, see Block Target File Methods

Model-Wide Target Files and System Target Files

You use model-wide target files on a model-wide basis. Model-wide target files provide basic information to TLC, which transforms the model.rtw file into target-specific code.

The system target file is the entry point for TLC. It is analogous to the main() routine of a C program. System target files oversee the entire code generation process. For example, the system target file grt.tlc sets up some variables for codegenentry.tlc, which is the entry point into the system target files. For a complete list of available system target files, see Compare System Target File Support Across Products.

Target File Usage

Use the target files to:

  • Inline an S-function

    Inlining an S-function means writing a block target file that instructs TLC how to generate code for that S-Function block. The compiler can generate code for noninlined C MEX S-functions. If you inline a C MEX S-function, the compiler can generate more efficient code. Noninlined C MEX S-functions execute by using the S-function application program interface (API) and can be inefficient. You can inline a MATLAB® file or Fortran S-function. TLC can generate code for the S-function in both cases.

  • Customize the code generated for all models

    You might want to instrument the generated code for profiling or make other changes to overall code generation for all models. To accomplish such changes, modify some of the system target files.

System Target Files

The entire code generation process starts with the single system target file that you specify in the Configuration Parameters dialog box, on the Code Generation pane. Click the Browse button to activate the system target file browser for this purpose. A close examination of a system target file reveals how code generation occurs. This listing is a listing of the non-comment lines in grt.tlc, the target file to generate code for a generic real-time executable.

%selectfile NULL_FILE
%assign TargetType = "RT" 
%assign Language   = "C"  
%assign MatFileLogging = 1 
%include "codegenentry.tlc"

The three variables, Language, TargetType, and MatFileLogging, are global TLC variables that other functions use. Code generation is then initiated by the call to codegenentry.tlc, the main entry point for code generation.

If you want to modify overall code generation, you must change the system target file. After the initial setup, instead of calling codegenentry.tlc, you must call your own TLC files. This code shows an example system target file called mygrt.tlc.

%% Set up variables, etc.
%% Load my library functions 
%% Note that mylib.tlc should %include funclib.tlc at the  
%% beginning. 
%include "mylib.tlc"  
%include "commonsetup.tlc"  

%% Next, you can include TLC files that you need for 
%% preprocessing information about the model and to fill in 
%% hooks. The following is an example of including a single
%% TLC file that contains custom hooks. 
%include "myhooks.tlc"  

%% Finally, call the code generator. 
%include "commonentry.tlc"

Generated code is placed in a model or subsystem function. The relevant generated function names and their execution order are described in Execution of Code Generated from a Model and Configure C Code Generation for Model Entry-Point Functions. During code generation, functions from each of the block target files are executed and the generated code is placed in model or subsystem functions.

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