Cortex-m3启动代码分析笔记

启动代码文件名是STM32F10X.S，它的作用先总结下，然后再分析。启动代码作用一般是：1）堆和栈的初始化；2）向量表定义；3）地址重映射及中断向量表的转移；4）设置系统时钟频率；5）中断寄存器的初始化；6）进入C应用程序。

   （1）按启动代码的次序，先看堆和栈的初始化：

Stack_Size      EQU     0x00000200       ；定义Stack_Size为0x00000200

                AREA    STACK, NOINIT, READWRITE, ALIGN=3   ；定义栈，可初始为0，8字节对齐
Stack_Mem       SPACE   Stack_Size       ；分配0x200个连续字节，并初始化为0
__initial_sp   ；汇编代码地址标号

 

Heap_Size       EQU     0x00000000

                AREA    HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem        SPACE   Heap_Size
__heap_limit

                PRESERVE8 ；指定当前文件堆栈8字节对齐
                THUMB     ；告诉汇编器下面是32为的Thumb指令，如果需要汇编器将插入位以保证对齐

  （2）中断向量表定义

AREA    RESET, DATA, READONLY ;定义复位向量段，只读
                EXPORT  __Vectors   ；定义一个可以在其他文件中使用的全局标号。此处表示中断地址

__Vectors       DCD     __initial_sp              ; 给__initial_sp分配4字节32位的地址0x0
                DCD     Reset_Handler             ; 给标号Reset Handler分配地址为0x00000004
                DCD     NMI_Handler               ; 给标号NMI Handler分配地址0x00000008
                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                         ; 这种形式就是保留地址，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 detect
                DCD     TAMPER_IRQHandler         ; Tamper
                DCD     RTC_IRQHandler            ; RTC
                DCD     FLASH_IRQHandler          ; Flash
                DCD     RCC_IRQHandler            ; RCC
                DCD     EXTI0_IRQHandler          ; EXTI Line 0
                DCD     EXTI1_IRQHandler          ; EXTI Line 1
                DCD     EXTI2_IRQHandler          ; EXTI Line 2
                DCD     EXTI3_IRQHandler          ; EXTI Line 3
                DCD     EXTI4_IRQHandler          ; EXTI Line 4
                DCD     DMAChannel1_IRQHandler    ; DMA Channel 1
                DCD     DMAChannel2_IRQHandler    ; DMA Channel 2
                DCD     DMAChannel3_IRQHandler    ; DMA Channel 3
                DCD     DMAChannel4_IRQHandler    ; DMA Channel 4
                DCD     DMAChannel5_IRQHandler    ; DMA Channel 5
                DCD     DMAChannel6_IRQHandler    ; DMA Channel 6
                DCD     DMAChannel7_IRQHandler    ; DMA Channel 7
                DCD     ADC_IRQHandler            ; ADC
                DCD     USB_HP_CAN_TX_IRQHandler  ; USB High Priority or CAN TX
                DCD     USB_LP_CAN_RX0_IRQHandler ; USB Low  Priority or CAN RX0
                DCD     CAN_RX1_IRQHandler        ; CAN RX1
                DCD     CAN_SCE_IRQHandler        ; CAN SCE
                DCD     EXTI9_5_IRQHandler        ; EXTI Line 9..5
                DCD     TIM1_BRK_IRQHandler       ; TIM1 Break
                DCD     TIM1_UP_IRQHandler        ; TIM1 Update
                DCD     TIM1_TRG_COM_IRQHandler   ; TIM1 Trigger and Commutation
                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      ; EXTI Line 15..10
                DCD     RTCAlarm_IRQHandler       ; RTC Alarm through EXTI Line
                DCD     USBWakeUp_IRQHandler      ; USB Wakeup from suspend

  （3）中断向量表的转移

AREA    |.text|, CODE, READONLY ；代码段定义

; Reset Handler

Reset_Handler   PROC ；标记一个函数的开始
                EXPORT  Reset_Handler             [WEAK]；[WEAK] 选项表示当所有的源文件都没有 定义这样一个标号时，编译器也不给出错误信息，在多数情况下将该标号置为 0 ，若该标号为 B 或 BL 指令引用，则将 B 或 BL指令置为 NOP 操作。EXPORT提示编译器该标号可以为外部文件引用。
                IMPORT  __main ;通知编译器要使用的标号在其他文件
                LDR     R0, =__main；使用“=”表示LDR目前是伪指令不是标准指令。这里是把__main的地址给RO。
                BX      R0；BX是ARM指令集和THUMB指令集之间程序的跳转
                ENDP

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

NMI_Handler     m  ;"m"其实就是PROC表示汇编函数的开始
                EXPORT  NMI_Handler               [WEAK]
                B       .
                ENDP
HardFault_Handler\      ;"\"是换行的意思
                PROC
                EXPORT  HardFault_Handler         [WEAK]
                B       . ;"."号到底是什么含义呢，目前还没查到资料。可能是保留地址，供以后修改的吧
                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

                EXPORT  WWDG_IRQHandler           [WEAK]
                EXPORT  PVD_IRQHandler            [WEAK]
                EXPORT  TAMPER_IRQHandler         [WEAK]
                EXPORT  RTC_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  DMAChannel1_IRQHandler    [WEAK]
                EXPORT  DMAChannel2_IRQHandler    [WEAK]
                EXPORT  DMAChannel3_IRQHandler    [WEAK]
                EXPORT  DMAChannel4_IRQHandler    [WEAK]
                EXPORT  DMAChannel5_IRQHandler    [WEAK]
                EXPORT  DMAChannel6_IRQHandler    [WEAK]
                EXPORT  DMAChannel7_IRQHandler    [WEAK]
                EXPORT  ADC_IRQHandler            [WEAK]
                EXPORT  USB_HP_CAN_TX_IRQHandler  [WEAK]
                EXPORT  USB_LP_CAN_RX0_IRQHandler [WEAK]
                EXPORT  CAN_RX1_IRQHandler        [WEAK]
                EXPORT  CAN_SCE_IRQHandler        [WEAK]
                EXPORT  EXTI9_5_IRQHandler        [WEAK]
                EXPORT  TIM1_BRK_IRQHandler       [WEAK]
                EXPORT  TIM1_UP_IRQHandler        [WEAK]
                EXPORT  TIM1_TRG_COM_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  RTCAlarm_IRQHandler       [WEAK]
                EXPORT  USBWakeUp_IRQHandler      [WEAK]

WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
RTC_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMAChannel1_IRQHandler
DMAChannel2_IRQHandler
DMAChannel3_IRQHandler
DMAChannel4_IRQHandler
DMAChannel5_IRQHandler
DMAChannel6_IRQHandler
DMAChannel7_IRQHandler
ADC_IRQHandler
USB_HP_CAN_TX_IRQHandler
USB_LP_CAN_RX0_IRQHandler
CAN_RX1_IRQHandler
CAN_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_IRQHandler
TIM1_UP_IRQHandler
TIM1_TRG_COM_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
RTCAlarm_IRQHandler
USBWakeUp_IRQHandler

                B       .

                ENDP
                ALIGN

  （4）堆和栈的初始化

IF      :DEF:__MICROLIB        ；“DEF”的用法——:DEF:X 就是说X定义了则为真，否则为假
                
                EXPORT  __initial_sp
                EXPORT  __heap_base
                EXPORT  __heap_limit
               
                ELSE
               
                IMPORT  __use_two_region_memory
                EXPORT  __user_initial_stackheap
__user_initial_stackheap

                LDR     R0, =  Heap_Mem
                LDR     R1, =(Stack_Mem + Stack_Size)
                LDR     R2, = (Heap_Mem +  Heap_Size)
                LDR     R3, = Stack_Mem
                BX      LR

                ALIGN ；填充字节使地址对齐

                ENDIF

END