📚 TLC
🌟 What is TLC?
TLC stands for Target Language Compiler.
It’s a scripting language used by MATLAB/Simulink (Embedded Coder) to customize and control code generation. TLC scripts determine how the Simulink model gets converted into C/C++ code.
🧠 Where is TLC used?
TLC is used primarily in: - Embedded Coder workflows - Simulink Coder - Target-specific code customization - Code generation for controllers in automotive, aerospace, medical, and industrial applications
🛠️ When and Why do we use TLC?
We use TLC when we want to: 1. Customize code generation: You can control how blocks, functions, or subsystems generate code. 2. Optimize generated code: Improve efficiency for embedded hardware by tweaking code output. 3. Support a specific target processor or RTOS. 4. Generate structured, readable, or MISRA C compliant code. 5. Integrate custom algorithms or hardware-specific APIs into the generated code.
🗂️ How is TLC used in practice?
Here’s the workflow:
- Simulink Model → Code generation is initiated using Embedded Coder.
- Code generator reads TLC scripts → These control how model elements translate to code.
- TLC reads block.tlc files for each Simulink block.
- You can write or override TLC files (e.g.,
myCustomBlock.tlc) to: - Add your own C functions
- Optimize output code for your system
- The generated C code is compiled and flashed to the embedded hardware.
📁 TLC File Types
- System Target File (
*.tlc): Describes the code generation process for the whole system. - Block TLC (
*.tlc): Used to define code generation for individual blocks. - Utility TLC files: Contain helper functions for the compiler.
💻 Example Use Case in Automotive
Let’s say you're working on an ECU controlling ambient lighting, and you want to:
- Replace default generated for loops with macros for efficiency
- Insert comments or debug information
- Integrate custom driver code for LIN communication
👉 You’d use TLC customization to change the generated C code format or integrate the driver-level logic into your application layer.
✅ Summary
| Item | Description |
|---|---|
| What | A scripting language for customizing Simulink code generation |
| Where | Used within Embedded Coder, Simulink Coder |
| When | During code generation from Simulink models |
| Why | To optimize, customize, or integrate code specific to your hardware or standard |
| How | By writing/editing .tlc scripts in the appropriate directories |
** 📋 TLC (Target Language Compiler) Interview Questions and Answers**
1. What is TLC in Simulink?
TLC (Target Language Compiler) is a scripting language used by Embedded Coder to customize and control how Simulink models are converted into C/C++ code.
2. Why is TLC important in Embedded Coder?
It gives developers control over code generation, enabling optimization, integration with custom hardware/software, and meeting coding standards like MISRA C.
3. What file extensions are used for TLC scripts?
.tlc — for both system target files and block-specific customization files.
4. Where are TLC files typically located?
Under MATLAB/rtw/c or within Embedded Coder installation folders, or custom folders added to the path.
5. What is a system target file?
A system target file (*.tlc) defines the overall behavior of code generation for a target platform, including compiler settings and scheduling.
6. What is the function of a block TLC file?
A block TLC file specifies how a Simulink block should generate code — especially when the default code is not optimal or sufficient.
7. Can you modify TLC files for built-in blocks?
Yes, but it’s recommended to copy the block, create a custom block, and apply TLC customization to avoid impacting built-in functionality.
8. What command is used to trace TLC execution?
Use the rtwtrace command or enable verbose build logging in Configuration Parameters to trace TLC behavior during code generation.
9. How do you debug TLC code?
By using %<LibReportError("message")> or by inserting breakpoints and using trace logs (verbose build mode).
10. What is the syntax of TLC?
TLC uses C-like syntax, with %<...> to embed TLC expressions and %if, %else, %foreach for control logic.
11. Can you call C functions from TLC?
Yes, you can generate calls to external C functions, but TLC itself cannot execute C code directly — it just instructs how to generate it.
12. How do you pass parameters to a TLC script?
Block parameters or model configuration settings can be passed to the TLC script via the code generation context.
13. What is LibBlockOutputSignal in TLC?
It's a library function that returns the output signal from a Simulink block during code generation.
14. What’s the difference between LibBlockInputs and LibBlockInputSignal?
- LibBlockInputs gives access to all inputs of a block.
- LibBlockInputSignal(index) accesses a specific input signal.
15. What does %implements do in TLC?
It declares that the TLC script is an implementation for a specific Simulink block and defines how it should generate code.
16. When would you write a custom block TLC?
When you want to generate optimized, specific code for a block — e.g., using hardware-specific macros, inline functions, or avoiding unnecessary logic.
17. Can you generate MISRA C compliant code using TLC?
Yes, by customizing the generated code via TLC to remove or modify constructs that violate MISRA rules.
18. What is the role of LibBlockCode in TLC?
It defines the main block code section for the block and is the most commonly overridden method in custom TLC scripts.
19. What does %%function Outputs mean in a TLC file?
It defines a function section that handles output signal generation in the generated code.
20. How does TLC interact with DWork vectors?
TLC can access and initialize DWork (Data Work) vectors for state or persistent variables in generated code using functions like LibBlockDWork.
21. How can you reuse code snippets across TLC files?
By defining utility functions in reusable TLC libraries and calling them from block-specific scripts.
22. Is it necessary to write TLC for every custom block?
Not always. If a block can use the default code generation path, custom TLC isn’t required.
23. What happens if a TLC file has an error?
Code generation will fail, and an error message is displayed in MATLAB’s console or diagnostics viewer.
24. What is the role of RTW.TflTable in relation to TLC?
It helps define a Target Function Library that maps Simulink operations to target-specific C code using TLC.
25. What is BuildInfo in TLC and when do you use it?
BuildInfo provides methods to add source files, include paths, and preprocessor definitions to the generated code.
26. What is the difference between TLC and M-script?
TLC is used during code generation; M-script (MATLAB code) is used for model configuration, scripting, and simulation.
27. Can TLC files define new data types?
No, TLC does not define new data types directly. You can reference or generate existing types supported in C code.
28. What are the typical sections in a TLC file?
%%Function Outputs, %%Function Start, %%Function Terminate, %%Function Update for various block behaviors.
29. What is the use of %roll directive?
It is similar to a loop construct in TLC to iterate over arrays or block parameters during code generation.
30. What is FEVAL in TLC?
FEVAL allows calling MATLAB functions from within a TLC script.
31. How do you include other TLC files?
Using %include "filename.tlc" to modularize and reuse TLC code.
32. Can TLC generate inline or separate C functions?
Yes, based on the block requirements and how the TLC is written.
33. What is the difference between LibSetRecordStatement and LibBlockCode?
- LibBlockCode: Generates core logic for the block.
- LibSetRecordStatement: Used for profiling or code instrumentation.
34. Can TLC be used for simulation purposes?
No. TLC is strictly for code generation; it does not affect simulation results.
35. What tools assist in developing and debugging TLC?
TLC debugger (rtwdemo_tlcdebug), Verbose build logs, and Diagnostic Viewer in MATLAB.
36. What is the use of CompOptions in TLC?
It contains compiler-specific options passed during build setup from the system target file.
37. What is GenRTWTargetInfo.m used for?
It registers a new system target file and related TLC files in MATLAB.
38. How do you add preprocessor macros in TLC?
Use buildInfo.addDefines('DEFINE_NAME') in your TLC script.
39. Can you control file placement with TLC?
Yes, using buildInfo APIs to set file destinations.
40. What is a .mk file in context with TLC?
It is a Makefile used during build, often generated by the TLC system target.
41. How do you link external libraries in TLC?
Use buildInfo.addLinkObjects or buildInfo.addIncludePaths in your TLC script.
42. Can you use TLC in standalone MATLAB without Simulink?
No. TLC is tied to Simulink code generation and Embedded Coder workflow.
43. What is sl_customization.m in relation to TLC?
Used to register custom block libraries and associate them with TLC implementations.
44. How can you disable TLC customization temporarily?
By removing the TLC file or renaming it so the code generator uses the default.
45. What is CoderInfo in TLC?
Provides metadata about the block’s code generation context.
46. Can you call MATLAB functions from within TLC?
Yes, using FEVAL, but it must return constant values at code generation time.
47. What is the impact of TLC errors on build process?
Errors in TLC will abort code generation. Logs must be checked for exact failure points.
48. Is TLC case-sensitive?
Yes. Variable names and file names are case-sensitive.
49. What is %openfile used for in TLC?
To open and write content to additional files during code generation.
50. What is %with block in TLC?
Used to create a temporary scope for a structure to simplify code readability.