Initialise stack, memory and clocks before main runs.
At reset the CPU loads the stack pointer and jumps to the reset handler, which initialises .data and .bss, sets clocks, calls constructors and then main(). A bootloader can load new firmware via UART/USB before launching the application. Vector table relocation is required.
Arduino bootloader flashes sketches over serial.
Startup code prepares the processor before main runs, so a wrong startup sequence causes failures that are hard to trace.
Initialise stack, memory and clocks before main runs.
Startup code prepares the processor before main runs, so a wrong startup sequence causes failures that are hard to trace.
It sets the stack pointer, copies initialised data from flash to RAM, zeroes the uninitialised data and calls the system initialisation before main.
It can update firmware and start the application safely, which is useful for field upgrades and recovery.
Typical applications include setting up the stack pointer and clearing RAM before the first line of C runs, configuring the system clock and PLL before running fast code and copying initial values from flash into RAM for global variables.
Study "Memory-mapped I/O" first (topic 72 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
Linker script. Vector table. Dual-bank updates.
Arduino bootloader flashes sketches over serial.
The next topic is "Power management", which builds directly on this one.
It is classed as Advanced in Electronics & Embedded (topic 73 of 104). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Electronics & Embedded.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.