STM32启动流程

1、上电执行启动文件startup_stm32f303xc.s

（1）Set the initial SP

（2）Set the initial PC == Reset_Handler

（3）Set the vector table entries with the exceptions ISR address

（4）Branches to __main in the C library (which eventually calls main()).

After Reset the CortexM4 processor is in Thread mode, priority is Privileged, and the Stack is set to Main.

; Reset handler
Reset_Handler    PROC
                 EXPORT  Reset_Handler             [WEAK]
IMPORT  SystemInit
IMPORT  __main


                 LDR     R0, =SystemInit
                 BLX     R0
                 LDR     R0, =__main
                 BX      R0
                 ENDP