ARM Cortex M3(V7-M架构)硬件启动程序 一

时间:2024-01-10 15:54:02

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)中断向量表定义;

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=   ;定义栈,可初始为0,8字节对齐  ;声明一个名为STACK的可读写段,8字节对齐
Stack_Mem       SPACE   Stack_Size        ;分配0x200个连续字节,并初始化为0          ;开辟一段大小为Stack_Size的内存空间
__initial_sp                              ;汇编代码地址标号                   ;地址标号,即STACK段空间顶地址

Heap_Size       EQU     0x00000000
                AREA    HEAP, NOINIT, READWRITE, ALIGN=
__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

由于Cortex m3设定每次上电复位后都从0x00地址处加载中断向量表,并且将中断向量表的第0个地址的数据加载入MSP作为栈顶地址。所以在中断向量表的第0个地址出填写__initial_sp即STACK段空间顶地址。

同时在MDK的工程属性页面里设定“片上只读地址的范围”0x00至0x80000;在 LINK选项卡里面选择使用从Target里面得到内存布局。这样RESET段都可以被链接至0x00地址处,而其中最开始的__Vectors地址标号所指定的__initial_sp,即STACK段空间顶地址,至此芯片就在上电后通过中断向量表将MSP的值设置为__initial_sp的值了。

(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                              ; 这种形式就是保留地址,不给任何标号分配
                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 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 

==============================================================================

“.”代表 address of current instruction 也就是当前指令地址

文中了(B   .)表示循环,有点像C里面的while(1);语句。