startup_stm32f407xx.s

使用单片机STM32执行的第一个程序是startup_stm32f407xx.s

指令名称 含义
EQU 给数字常量取一个符号名,相当于C语言中的define
AREA 汇编一个新的代码段或者数据段
SPACE 分配内存空间
PRESERVE8 当前文件堆栈需按照8字节对齐
EXPORT 声明一个具有全局属性的标号,可被外部文件使用
IMPORT 声明一个来自外部文件的标号
DCD 以字为单位分配内存,要求4字节对齐,并要求初始化这些内存
PROC 定义子程序,与ENDP成对使用
ENDP 表示子程序结束
WEAK 弱定义,如果外部文件定义了一个标号,则优先使用外部文件的标号,是ARM伪指令
ALIGN 编译器对指令或数据的存放地址进行对齐,缺省表示4字节对齐,是ARM伪指令
IF,ELSE,ENDIF 汇编条件分支语句,同C语言的类似
LDR 从存储器中加载字到一个寄存器中
B 跳转到一个标号
BL 跳转到由寄存器/标号给出的地址,并保存跳转前的下条指令至LR中
BX 跳转到由寄存器/标号给出的地址,并根据寄存器的LSE确定处理器的状态
BLX 跳转到由寄存器/标号给出的地址,并根据寄存器的LSE确定处理器的状态,同时保存跳转前的下条指令至LR中
END 到达文件的末尾,文件结束

启动文件的作用
1:初始化堆栈指针
2:初始化PC指针 = Reset Handler
3:初始化中断向量表
4:配置系统时钟
5:调用C库函数__main 最终进入c程序空间main

//1-配置栈
Stack_Size      EQU     0x00000400 //stack_size = 0x00000400  1KB

                AREA    STACK, NOINIT, READWRITE, ALIGN=3//定义栈区,不初始化,可读可写,2^8字节对齐
Stack_Mem       SPACE   Stack_Size//分配stack_size大小的空间,Stack_mem是分配空间的起始位置,即栈底的地址
__initial_sp //地址标号,表示栈的结束地址,用来指向栈顶地址

//2-堆配置
Heap_Size       EQU     0x00000200//Heap_size = 0x00000200

                AREA    HEAP, NOINIT, READWRITE, ALIGN=3//定义堆区,不初始化,可读可写,2^8字节对齐
__heap_base//地址标号,用来指向堆的起始地址
Heap_Mem        SPACE   Heap_Size//分配Heap_Size大小的空间,Heap_mem是分配空间的起始地址
__heap_limit//地址标号,用来指向堆的结束地址

                PRESERVE8//当前文件的堆栈8字节对齐
                THUMB//告诉编译器下面兼容32位Thumb指令(老版本指令)

//3-初始化中断向量表, 产生中断后会跳到中断向量表中对应的地址
; Vector Table Mapped to Address 0 at Reset
                AREA    RESET, DATA, READONLY//定义复位区,只读,
                EXPORT  __Vectors//定义可在其他文件使用的全局标号,此处表示中断向量表的地址 (默认在falsh中的起始位置0x08000000)
                EXPORT  __Vectors_End//定义可在其他文件使用的全局标号,此处表示中断向量表的结束地址
                EXPORT  __Vectors_Size//定义可在其他文件使用的全局标号,此处表示中断向量表的大小

__Vectors       DCD     __initial_sp               ; Top of Stack//分配四字节空间,存放标号_inital_sp的地址
                DCD     Reset_Handler              ; Reset Handler//分配四字节空间,存放标号Reset_Handler的地址
                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     0                          ; Reserved//保留,不给任何标号分配
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     0                          ; Reserved
                DCD     SVC_Handler                ; SVCall Handler
                DCD     DebugMon_Handler           ; Debug Monitor Handler
                DCD     0                          ; 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                                             
                DCD     DMA1_Stream0_IRQHandler           ; DMA1 Stream 0                                   
                DCD     DMA1_Stream1_IRQHandler           ; DMA1 Stream 1                                   
                DCD     DMA1_Stream2_IRQHandler           ; DMA1 Stream 2                                   
                DCD     DMA1_Stream3_IRQHandler           ; DMA1 Stream 3                                   
                DCD     DMA1_Stream4_IRQHandler           ; DMA1 Stream 4                                   
                DCD     DMA1_Stream5_IRQHandler           ; DMA1 Stream 5                                   
                DCD     DMA1_Stream6_IRQHandler           ; DMA1 Stream 6                                   
                DCD     ADC_IRQHandler                    ; ADC1, ADC2 and ADC3s                            
                DCD     CAN1_TX_IRQHandler                ; CAN1 TX                                                
                DCD     CAN1_RX0_IRQHandler               ; CAN1 RX0                                               
                DCD     CAN1_RX1_IRQHandler               ; CAN1 RX1                                               
                DCD     CAN1_SCE_IRQHandler               ; CAN1 SCE                                               
                DCD     EXTI9_5_IRQHandler                ; External Line[9:5]s                                    
                DCD     TIM1_BRK_TIM9_IRQHandler          ; TIM1 Break and TIM9                   
                DCD     TIM1_UP_TIM10_IRQHandler          ; TIM1 Update and TIM10                 
                DCD     TIM1_TRG_COM_TIM11_IRQHandler     ; TIM1 Trigger and Commutation and TIM11
                DCD     TIM1_CC_IRQHandler                ; TIM1 Capture Compare                                   
                DCD     TIM2_IRQHandler                   ; TIM2                                            
                DCD     TIM3_IRQHandler                   ; TIM3                                            
                DCD     TIM4_IRQHandler                   ; TIM4                                            
                DCD     I2C1_EV_IRQHandler                ; I2C1 Event                                             
                DCD     I2C1_ER_IRQHandler                ; I2C1 Error                                             
                DCD     I2C2_EV_IRQHandler                ; I2C2 Event                                             
                DCD     I2C2_ER_IRQHandler                ; I2C2 Error                                               
                DCD     SPI1_IRQHandler                   ; SPI1                                            
                DCD     SPI2_IRQHandler                   ; SPI2                                            
                DCD     USART1_IRQHandler                 ; USART1                                          
                DCD     USART2_IRQHandler                 ; USART2                                          
                DCD     USART3_IRQHandler                 ; USART3                                          
                DCD     EXTI15_10_IRQHandler              ; External Line[15:10]s                                  
                DCD     RTC_Alarm_IRQHandler              ; RTC Alarm (A and B) through EXTI Line                  
                DCD     OTG_FS_WKUP_IRQHandler            ; USB OTG FS Wakeup through EXTI line                        
                DCD     TIM8_BRK_TIM12_IRQHandler         ; TIM8 Break and TIM12                  
                DCD     TIM8_UP_TIM13_IRQHandler          ; TIM8 Update and TIM13                 
                DCD     TIM8_TRG_COM_TIM14_IRQHandler     ; TIM8 Trigger and Commutation and TIM14
                DCD     TIM8_CC_IRQHandler                ; TIM8 Capture Compare                                   
                DCD     DMA1_Stream7_IRQHandler           ; DMA1 Stream7                                           
                DCD     FMC_IRQHandler                    ; FMC                                             
                DCD     SDIO_IRQHandler                   ; SDIO                                            
                DCD     TIM5_IRQHandler                   ; TIM5                                            
                DCD     SPI3_IRQHandler                   ; SPI3                                            
                DCD     UART4_IRQHandler                  ; UART4                                           
                DCD     UART5_IRQHandler                  ; UART5                                           
                DCD     TIM6_DAC_IRQHandler               ; TIM6 and DAC1&2 underrun errors                   
                DCD     TIM7_IRQHandler                   ; TIM7                   
                DCD     DMA2_Stream0_IRQHandler           ; DMA2 Stream 0                                   
                DCD     DMA2_Stream1_IRQHandler           ; DMA2 Stream 1                                   
                DCD     DMA2_Stream2_IRQHandler           ; DMA2 Stream 2                                   
                DCD     DMA2_Stream3_IRQHandler           ; DMA2 Stream 3                                   
                DCD     DMA2_Stream4_IRQHandler           ; DMA2 Stream 4                                   
                DCD     ETH_IRQHandler                    ; Ethernet                                        
                DCD     ETH_WKUP_IRQHandler               ; Ethernet Wakeup through EXTI line                      
                DCD     CAN2_TX_IRQHandler                ; CAN2 TX                                                
                DCD     CAN2_RX0_IRQHandler               ; CAN2 RX0                                               
                DCD     CAN2_RX1_IRQHandler               ; CAN2 RX1                                               
                DCD     CAN2_SCE_IRQHandler               ; CAN2 SCE                                               
                DCD     OTG_FS_IRQHandler                 ; USB OTG FS                                      
                DCD     DMA2_Stream5_IRQHandler           ; DMA2 Stream 5                                   
                DCD     DMA2_Stream6_IRQHandler           ; DMA2 Stream 6                                   
                DCD     DMA2_Stream7_IRQHandler           ; DMA2 Stream 7                                   
                DCD     USART6_IRQHandler                 ; USART6                                           
                DCD     I2C3_EV_IRQHandler                ; I2C3 event                                             
                DCD     I2C3_ER_IRQHandler                ; I2C3 error                                             
                DCD     OTG_HS_EP1_OUT_IRQHandler         ; USB OTG HS End Point 1 Out                      
                DCD     OTG_HS_EP1_IN_IRQHandler          ; USB OTG HS End Point 1 In                       
                DCD     OTG_HS_WKUP_IRQHandler            ; USB OTG HS Wakeup through EXTI                         
                DCD     OTG_HS_IRQHandler                 ; USB OTG HS                                      
                DCD     DCMI_IRQHandler                   ; DCMI  
                DCD     0                                 ; Reserved				                              
                DCD     HASH_RNG_IRQHandler               ; Hash and Rng
                DCD     FPU_IRQHandler                    ; FPU
                
                                         
__Vectors_End//中断向量表结束的位置

__Vectors_Size  EQU  __Vectors_End - __Vectors//计算得出中断向量表的大小,赋值给__Vectors_Size

                AREA    |.text|, CODE, READONLY//定义代码段,只读
//4-复位中断程序
Reset_Handler    PROC//函数开始
                 EXPORT  Reset_Handler             [WEAK]//本函数外部可以应用,[WAKE]表示弱定义 与编译器Keil相关
                 IMPORT  SystemInit//声明使用外部函数SystemInit
                 IMPORT  __main//声明使用外部函数__main

                 LDR     R0, =SystemInit//把函数地址赋值给寄存器R0
                 BLX     R0//跳到R0地址处执行该地址上的函数SystemInit
                 LDR     R0, =__main//把函数地址赋值给寄存器R0
                 BX      R0//跳到R0地址处执行该地址上的函数__main
                 ENDP//函数结束

; Dummy Exception Handlers (infinite loops which can be modified)
//5-中断服务函数
/*下面的函数一样,先声明可以外部使用,并可以在C语言中重新实现。实现了就执行C中实现的,没有实现, 就执行这里的。通过B.相当于while(1), 现象是卡死*/
NMI_Handler     PROC
                EXPORT  NMI_Handler                [WEAK]
                B       .
                ENDP
HardFault_Handler\
                PROC
                EXPORT  HardFault_Handler          [WEAK]
                B       .
                ENDP
MemManage_Handler\
                PROC
                EXPORT  MemManage_Handler          [WEAK]
                B       .
                ENDP
BusFault_Handler\
                PROC
                EXPORT  BusFault_Handler           [WEAK]
                B       .
                ENDP
UsageFault_Handler\
                PROC
                EXPORT  UsageFault_Handler         [WEAK]
                B       .
                ENDP
SVC_Handler     PROC
                EXPORT  SVC_Handler                [WEAK]
                B       .
                ENDP
DebugMon_Handler\
                PROC
                EXPORT  DebugMon_Handler           [WEAK]
                B       .
                ENDP
PendSV_Handler  PROC
                EXPORT  PendSV_Handler             [WEAK]
                B       .
                ENDP
SysTick_Handler PROC
                EXPORT  SysTick_Handler            [WEAK]
                B       .
                ENDP

Default_Handler PROC//函数开始
/*下面是中断的函数,先把符号声明为外部可以用,[WEAK] 代表弱应用。表示如果外部有该标号有定义则使用外部的函数来表示真正的中断处理函数*/
                EXPORT  WWDG_IRQHandler                   [WEAK]                                        
                EXPORT  PVD_IRQHandler                    [WEAK]                      
                EXPORT  TAMP_STAMP_IRQHandler             [WEAK]         
                EXPORT  RTC_WKUP_IRQHandler               [WEAK]                     
                EXPORT  FLASH_IRQHandler                  [WEAK]                                         
                EXPORT  RCC_IRQHandler                    [WEAK]                                            
                EXPORT  EXTI0_IRQHandler                  [WEAK]                                            
                EXPORT  EXTI1_IRQHandler                  [WEAK]                                             
                EXPORT  EXTI2_IRQHandler                  [WEAK]                                            
                EXPORT  EXTI3_IRQHandler                  [WEAK]                                           
                EXPORT  EXTI4_IRQHandler                  [WEAK]                                            
                EXPORT  DMA1_Stream0_IRQHandler           [WEAK]                                
                EXPORT  DMA1_Stream1_IRQHandler           [WEAK]                                   
                EXPORT  DMA1_Stream2_IRQHandler           [WEAK]                                   
                EXPORT  DMA1_Stream3_IRQHandler           [WEAK]                                   
                EXPORT  DMA1_Stream4_IRQHandler           [WEAK]                                   
                EXPORT  DMA1_Stream5_IRQHandler           [WEAK]                                   
                EXPORT  DMA1_Stream6_IRQHandler           [WEAK]                                   
                EXPORT  ADC_IRQHandler                    [WEAK]                         
                EXPORT  CAN1_TX_IRQHandler                [WEAK]                                                
                EXPORT  CAN1_RX0_IRQHandler               [WEAK]                                               
                EXPORT  CAN1_RX1_IRQHandler               [WEAK]                                                
                EXPORT  CAN1_SCE_IRQHandler               [WEAK]                                                
                EXPORT  EXTI9_5_IRQHandler                [WEAK]                                    
                EXPORT  TIM1_BRK_TIM9_IRQHandler          [WEAK]                  
                EXPORT  TIM1_UP_TIM10_IRQHandler          [WEAK]                
                EXPORT  TIM1_TRG_COM_TIM11_IRQHandler     [WEAK] 
                EXPORT  TIM1_CC_IRQHandler                [WEAK]                                   
                EXPORT  TIM2_IRQHandler                   [WEAK]                                            
                EXPORT  TIM3_IRQHandler                   [WEAK]                                            
                EXPORT  TIM4_IRQHandler                   [WEAK]                                            
                EXPORT  I2C1_EV_IRQHandler                [WEAK]                                             
                EXPORT  I2C1_ER_IRQHandler                [WEAK]                                             
                EXPORT  I2C2_EV_IRQHandler                [WEAK]                                            
                EXPORT  I2C2_ER_IRQHandler                [WEAK]                                               
                EXPORT  SPI1_IRQHandler                   [WEAK]                                           
                EXPORT  SPI2_IRQHandler                   [WEAK]                                            
                EXPORT  USART1_IRQHandler                 [WEAK]                                          
                EXPORT  USART2_IRQHandler                 [WEAK]                                          
                EXPORT  USART3_IRQHandler                 [WEAK]                                         
                EXPORT  EXTI15_10_IRQHandler              [WEAK]                                  
                EXPORT  RTC_Alarm_IRQHandler              [WEAK]                  
                EXPORT  OTG_FS_WKUP_IRQHandler            [WEAK]                        
                EXPORT  TIM8_BRK_TIM12_IRQHandler         [WEAK]                 
                EXPORT  TIM8_UP_TIM13_IRQHandler          [WEAK]                 
                EXPORT  TIM8_TRG_COM_TIM14_IRQHandler     [WEAK] 
                EXPORT  TIM8_CC_IRQHandler                [WEAK]                                   
                EXPORT  DMA1_Stream7_IRQHandler           [WEAK]                                          
                EXPORT  FMC_IRQHandler                    [WEAK]                                             
                EXPORT  SDIO_IRQHandler                   [WEAK]                                             
                EXPORT  TIM5_IRQHandler                   [WEAK]                                             
                EXPORT  SPI3_IRQHandler                   [WEAK]                                             
                EXPORT  UART4_IRQHandler                  [WEAK]                                            
                EXPORT  UART5_IRQHandler                  [WEAK]                                            
                EXPORT  TIM6_DAC_IRQHandler               [WEAK]                   
                EXPORT  TIM7_IRQHandler                   [WEAK]                    
                EXPORT  DMA2_Stream0_IRQHandler           [WEAK]                                  
                EXPORT  DMA2_Stream1_IRQHandler           [WEAK]                                   
                EXPORT  DMA2_Stream2_IRQHandler           [WEAK]                                    
                EXPORT  DMA2_Stream3_IRQHandler           [WEAK]                                    
                EXPORT  DMA2_Stream4_IRQHandler           [WEAK]                                 
                EXPORT  ETH_IRQHandler                    [WEAK]                                         
                EXPORT  ETH_WKUP_IRQHandler               [WEAK]                     
                EXPORT  CAN2_TX_IRQHandler                [WEAK]                                               
                EXPORT  CAN2_RX0_IRQHandler               [WEAK]                                               
                EXPORT  CAN2_RX1_IRQHandler               [WEAK]                                               
                EXPORT  CAN2_SCE_IRQHandler               [WEAK]                                               
                EXPORT  OTG_FS_IRQHandler                 [WEAK]                                       
                EXPORT  DMA2_Stream5_IRQHandler           [WEAK]                                   
                EXPORT  DMA2_Stream6_IRQHandler           [WEAK]                                   
                EXPORT  DMA2_Stream7_IRQHandler           [WEAK]                                   
                EXPORT  USART6_IRQHandler                 [WEAK]                                           
                EXPORT  I2C3_EV_IRQHandler                [WEAK]                                              
                EXPORT  I2C3_ER_IRQHandler                [WEAK]                                              
                EXPORT  OTG_HS_EP1_OUT_IRQHandler         [WEAK]                      
                EXPORT  OTG_HS_EP1_IN_IRQHandler          [WEAK]                      
                EXPORT  OTG_HS_WKUP_IRQHandler            [WEAK]                        
                EXPORT  OTG_HS_IRQHandler                 [WEAK]                                      
                EXPORT  DCMI_IRQHandler                   [WEAK]                                                                                 
                EXPORT  HASH_RNG_IRQHandler               [WEAK]
                EXPORT  FPU_IRQHandler                    [WEAK]
/*否则就使用下面的函数,来表示中断处理函数,下面的函数都是空的,没有任何有意义的执行指令,只会执行到B. 进入死循环中*/                
WWDG_IRQHandler                                                       
PVD_IRQHandler                                      
TAMP_STAMP_IRQHandler                  
RTC_WKUP_IRQHandler                                
FLASH_IRQHandler                                                       
RCC_IRQHandler                                                            
EXTI0_IRQHandler                                                          
EXTI1_IRQHandler                                                           
EXTI2_IRQHandler                                                          
EXTI3_IRQHandler                                                         
EXTI4_IRQHandler                                                          
DMA1_Stream0_IRQHandler                                       
DMA1_Stream1_IRQHandler                                          
DMA1_Stream2_IRQHandler                                          
DMA1_Stream3_IRQHandler                                          
DMA1_Stream4_IRQHandler                                          
DMA1_Stream5_IRQHandler                                          
DMA1_Stream6_IRQHandler                                          
ADC_IRQHandler                                         
CAN1_TX_IRQHandler                                                            
CAN1_RX0_IRQHandler                                                          
CAN1_RX1_IRQHandler                                                           
CAN1_SCE_IRQHandler                                                           
EXTI9_5_IRQHandler                                                
TIM1_BRK_TIM9_IRQHandler                        
TIM1_UP_TIM10_IRQHandler                      
TIM1_TRG_COM_TIM11_IRQHandler  
TIM1_CC_IRQHandler                                               
TIM2_IRQHandler                                                           
TIM3_IRQHandler                                                           
TIM4_IRQHandler                                                           
I2C1_EV_IRQHandler                                                         
I2C1_ER_IRQHandler                                                         
I2C2_EV_IRQHandler                                                        
I2C2_ER_IRQHandler                                                           
SPI1_IRQHandler                                                          
SPI2_IRQHandler                                                           
USART1_IRQHandler                                                       
USART2_IRQHandler                                                       
USART3_IRQHandler                                                      
EXTI15_10_IRQHandler                                            
RTC_Alarm_IRQHandler                            
OTG_FS_WKUP_IRQHandler                                
TIM8_BRK_TIM12_IRQHandler                      
TIM8_UP_TIM13_IRQHandler                       
TIM8_TRG_COM_TIM14_IRQHandler  
TIM8_CC_IRQHandler                                               
DMA1_Stream7_IRQHandler                                                 
FMC_IRQHandler                                                            
SDIO_IRQHandler                                                            
TIM5_IRQHandler                                                            
SPI3_IRQHandler                                                            
UART4_IRQHandler                                                          
UART5_IRQHandler                                                          
TIM6_DAC_IRQHandler                            
TIM7_IRQHandler                              
DMA2_Stream0_IRQHandler                                         
DMA2_Stream1_IRQHandler                                          
DMA2_Stream2_IRQHandler                                           
DMA2_Stream3_IRQHandler                                           
DMA2_Stream4_IRQHandler                                        
ETH_IRQHandler                                                         
ETH_WKUP_IRQHandler                                
CAN2_TX_IRQHandler                                                           
CAN2_RX0_IRQHandler                                                          
CAN2_RX1_IRQHandler                                                          
CAN2_SCE_IRQHandler                                                          
OTG_FS_IRQHandler                                                    
DMA2_Stream5_IRQHandler                                          
DMA2_Stream6_IRQHandler                                          
DMA2_Stream7_IRQHandler                                          
USART6_IRQHandler                                                        
I2C3_EV_IRQHandler                                                          
I2C3_ER_IRQHandler                                                          
OTG_HS_EP1_OUT_IRQHandler                           
OTG_HS_EP1_IN_IRQHandler                            
OTG_HS_WKUP_IRQHandler                                
OTG_HS_IRQHandler                                                   
DCMI_IRQHandler                                                                                                             
HASH_RNG_IRQHandler
FPU_IRQHandler  
           
                B. //while(1)

                ENDP//函数结束

                ALIGN
//6- 堆栈的初始化,这个由c库函数_main来实现的,来确定堆和栈的起始地址
;*******************************************************************************
; User Stack and Heap initialization
;*******************************************************************************
                 IF      :DEF:__MICROLIB//如果定义了__MICROLIB,则为真,否则为假,目前未定义,在Keil中的target中开启
                //如果定义了,那么下面栈定指针,堆起始地址,堆结束地址,可以由外部程序来使用,定义
                 EXPORT  __initial_sp
                 EXPORT  __heap_base
                 EXPORT  __heap_limit
                
                 ELSE
                
                 IMPORT  __use_two_region_memory//使用外部函数  由用户自己实现堆栈地址的初始化,参考ARM Developement Tools
                 EXPORT  __user_initial_stackheap//声明全局符号
                 
__user_initial_stackheap

                 LDR     R0, =  Heap_Mem//堆的起始地址
                 LDR     R1, =(Stack_Mem + Stack_Size)//栈的起始地址+栈的大小=栈的结束地址
                 LDR     R2, = (Heap_Mem +  Heap_Size)//堆的起始地址+堆的带下=堆的结束地址
                 LDR     R3, = Stack_Mem//栈起始的地址
                 BX      LR//跳到返回地址执行

                 ALIGN

                 ENDIF

                 END

;************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE*****

stm32f407的有片内flash和ram, 那么上面利用AREA 分配的区域,读写的一般位于RAM上,只读一般位于flash上

STACK 段和HEAP段是读写,位于RAM上,RAM的起始是0x20000000
RSET段和 .text段是只读,位于flash上 lash的起始地址是0x08000000

通过这两个图可以看出,0x8000000放的是RESET

在.s文件中定义的段
startup_stm32f407xx.s_第1张图片
在map文件中查看RESET段的真实存储位置
startup_stm32f407xx.s_第2张图片
在map文件中查看堆和栈的具体位置
startup_stm32f407xx.s_第3张图片
可读写的数据在ram会从0x20000000的位置开始存放。首先存放datta段和bss段。当这些段存放完成后的结束地址就是堆的起始地址,如上图的HEAP,Heap_Mem。再根据.s文件中定义的堆的大小,堆的结束地址就确定了,紧挨着堆的就是栈的地址STACK, Stack_Mem,堆的大小也在.s文件中确定了,那么__initial_sp这个指向栈最高位置的地址也能确定了。如下图
startup_stm32f407xx.s_第4张图片

总结:STM32启动文件,首先定义了栈和堆的大小,并在代码区定义中断向量表,表中第一个是栈顶地址,第二个是复位中段的程序的入口,Reset_Handler是系统上电后自动跳转至该处,然后开始执行其后的相关代码,其中_main并非C中的main函数,而是C库函数,其会初始化栈、堆,配置系统环境,在函数的最后调用用户编写的main函数,进入C的世界。

用户堆栈初始化由C库函数__main完成,__MICROLIB由KEIL里面开启,__use_two_region_memory由用户自己实现。

    一般而言,系统上电后第一个执行的是由汇编所编写的启动文件,其主要工作为一下五部分:

  (1)、初始化堆栈指针SP=_initial_sp

  (2)、初始化PC指针,令其=Reset_Handler

  (3)、初始化中断向量表

  (4)、配置系统时钟 //位于system_stm32f4xx.c中的SystemInit()

  (5)、调用C库函数_main初始化用户堆栈,从而最终调用main函数进入C的世界

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