启动文件startup_stm32f40_41xxx.s

一、启动文件，startup_stm32f40x_41xx.s

1、定义

启动文件由汇编编写，是系统上电复位后第一执行的程序。

Stack_Size      EQU     0x00000400　　// 栈的大小可以调整

                AREA    STACK, NOINIT, READWRITE, ALIGN=
Stack_Mem       SPACE   Stack_Size
__initial_sp

; <h> Heap Configuration
;   <o>  Heap Size (in Bytes) <0x0-0xFFFFFFFF:>
; </h>

Heap_Size       EQU     0x00000200

                AREA    HEAP, NOINIT, READWRITE, ALIGN=
__heap_base
Heap_Mem        SPACE   Heap_Size
__heap_limit

                PRESERVE8
                THUMB

; Vector Table Mapped to Address  at Reset
                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors
                EXPORT  __Vectors_End
                EXPORT  __Vectors_Size

__Vectors       DCD     __initial_sp               ; Top of Stack
                DCD     Reset_Handler              ; Reset Handler
                DCD     NMI_Handler                ; NMI Handler
                DCD     HardFault_Handler          ; Hard Fault Handler
                DCD     MemManage_Handler          ; MPU Fault Handler
                DCD     BusFault_Handler           ; Bus Fault Handler
                DCD     UsageFault_Handler         ; Usage Fault Handler

__Vectors_End

__Vectors_Size  EQU  __Vectors_End - __Vectors

                AREA    |.text|, CODE, READONLY

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

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

; Dummy Exception Handlers (infinite loops which can be modified)

NMI_Handler     PROC

2、特征

1）初始化堆栈指针，主要是为C语言提供良好的运行环境

2）进行复位处理，执行该Reset_Handler函数

3）初始化向量表，中断入口地址列表

4）配置系统的时钟，调用SystemInit

5）调用C库函数__main进入main.c中的main函数执行

二、异常向量表

1、8051

AT89S51共有5个中断源，2个外部中断、2个定时器中断、1个串口中断。

中断入口地址
外部中断0                             0003H
定时器0                               000BH
外部中断1                             0013H
定时器1                               001BH
串口中断                               0023H

2、ARM Cortex-M4

汇编文件当中的异常量表（中断入口地址的集合）

; Vector Table Mapped to Address  at Reset
                AREA    RESET, DATA, READONLY
                EXPORT  __Vectors
                EXPORT  __Vectors_End
                EXPORT  __Vectors_Size

__Vectors       DCD     __initial_sp               ; Top of Stack
                DCD     Reset_Handler              ; Reset Handler
                DCD     NMI_Handler                ; NMI Handler
                DCD     HardFault_Handler          ; Hard Fault Handler
                DCD     MemManage_Handler          ; MPU Fault Handler
                DCD     BusFault_Handler           ; Bus Fault Handler
                DCD     UsageFault_Handler         ; Usage Fault Handler
                DCD                               ; Reserved
                DCD                               ; Reserved
                DCD                               ; Reserved
                DCD                               ; Reserved
                DCD     SVC_Handler                ; SVCall Handler
                DCD     DebugMon_Handler           ; Debug Monitor Handler
                DCD                               ; Reserved
                DCD     PendSV_Handler             ; PendSV Handler
                DCD     SysTick_Handler            ; SysTick Handler

                ; External Interrupts
                DCD     WWDG_IRQHandler                   ; Window WatchDog
                DCD     PVD_IRQHandler                    ; PVD through EXTI Line detection
                DCD     TAMP_STAMP_IRQHandler             ; Tamper and TimeStamps through the EXTI line
                DCD     RTC_WKUP_IRQHandler               ; RTC Wakeup through the EXTI line
                DCD     FLASH_IRQHandler                  ; FLASH
                DCD     RCC_IRQHandler                    ; RCC
                DCD     EXTI0_IRQHandler                  ; EXTI Line0
                DCD     EXTI1_IRQHandler                  ; EXTI Line1
                DCD     EXTI2_IRQHandler                  ; EXTI Line2
                DCD     EXTI3_IRQHandler                  ; EXTI Line3
                DCD     EXTI4_IRQHandler                  ; EXTI Line4     

               .............................
                EXPORT  EXTI0_IRQHandler                  [WEAK] 

EXTI0_IRQHandler             //空函数    

WEAK的关键字

如果外部没有定义EXTI0_IRQHandler，就使用当前的EXTI0_IRQHandler。如果在外面定义了EXTI0_IRQHandler就执行外面定义好的函数。