STM32学习1（RCC时钟树）

　　arm汇编启动文件。

　　汇编注释用";"

;* - Set the initial SP　　　　　
;* - Set the initial PC == Reset_Handler
;* - Set the vector table entries with the exceptions ISR address
;* - Configure the system clock and the external SRAM/SDRAM mounted on STM324x9I-EVAL boards to be used as data memory (optional, to be enabled by user)
;* - Branches to __main in the C library (which eventually calls main()).
　　