Startup Code
Understand what happens before main(), including stack setup, vector-table use, data initialization and zeroing of BSS.
CORE IDEA
Startup behavior is architecture and toolchain dependent; inspect the startup file supplied for the target.
WHY IT MATTERS
Embedded firmware sits directly between C language rules and hardware behavior.
ENGINEERING VIEW
Check the compiler, architecture reference manual and peripheral documentation together.
DEBUG
Verify the generated behavior with registers, debugger state and physical measurements.
Engineer’s checklist
- Read the MCU reference manual before coding.
- Identify the exact register, field, access width and reset value.
- Protect unrelated bits and respect reserved-bit rules.
- Build with warnings enabled and inspect diagnostics.
- Verify the result on the target hardware.
KEY TAKEAWAY
Startup behavior is architecture and toolchain dependent; inspect the startup file supplied for the target.