Understand embedded startup code in depth from reset handlers to memory initialization with 5 critical insights engineers must know. Perfect for beginners and pros alike!
What is Startup Code? | Beginner-Friendly Guide
Startup code is a small but essential piece of code that runs before your main program starts. It prepares your system so that your program can run smoothly. This is especially important in embedded systems and low-level programming.
Simple Definition :
Startup code is the very first code that executes when a device is powered on or reset. It sets up the environment so that the
main()function can run properly.
Why is Startup Code Important?
Think of startup code as a stage crew in a play. Before the actors come on stage, the crew sets the lighting, positions the props, and makes sure everything is ready. Similarly, startup code:
- Sets up memory sections like
.data,.bss, and stack - Initializes hardware components if needed
- Calls constructors (in C++)
- Finally, it jumps to the
main()function
What Does Startup Code Typically Do?
- Set the Stack Pointer
Sets the stack to a known location in RAM. - Initialize Data Section
Copies initialized global variables from Flash to RAM. - Zero out the BSS Section
Sets all uninitialized global and static variables to zero. - Call System Initialization Code
Optional hardware-specific setup. - Call
main()Function
After everything is set up, control is passed to your program’smain()function.
Where is Startup Code Found?
- In embedded systems, startup code is usually written in assembly or C.
- It is provided by the compiler toolchain (like GCC, Keil, etc.) or custom-written for a specific microcontroller.
Conclusion
Startup code may not be visible when writing high-level programs, but it plays a crucial role behind the scenes. Especially in embedded development, understanding how startup code works can help you debug issues, customize behavior, and build better systems.
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Special thanks to @embedded-prep for contributing to this article on Embedded Prep
Mr. Raj Kumar is a highly experienced Technical Content Engineer with 7 years of dedicated expertise in the intricate field of embedded systems. At Embedded Prep, Raj is at the forefront of creating and curating high-quality technical content designed to educate and empower aspiring and seasoned professionals in the embedded domain.
Throughout his career, Raj has honed a unique skill set that bridges the gap between deep technical understanding and effective communication. His work encompasses a wide range of educational materials, including in-depth tutorials, practical guides, course modules, and insightful articles focused on embedded hardware and software solutions. He possesses a strong grasp of embedded architectures, microcontrollers, real-time operating systems (RTOS), firmware development, and various communication protocols relevant to the embedded industry.
Raj is adept at collaborating closely with subject matter experts, engineers, and instructional designers to ensure the accuracy, completeness, and pedagogical effectiveness of the content. His meticulous attention to detail and commitment to clarity are instrumental in transforming complex embedded concepts into easily digestible and engaging learning experiences. At Embedded Prep, he plays a crucial role in building a robust knowledge base that helps learners master the complexities of embedded technologies.
