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STM32 keil mdk启动代码发分析

在启动文件我们看到了__main和用户写的main,这2个是有区别的,大概流程如下:


1、复位第一条指令:Reset_Handler   PROC,这里指定为 LDR     R0, =__main。表示调用库函数__main,当然,我们可以在__main前做点事情,比如PLL初始化等。

2、__main()的执行流程参考:

http://www.rritw.com/a/bianchengyuyan/_NET/20120611/128129.html

跟一下汇编,大概是__scatterload()->__rt_entry()->__user_setup_stackheap()

3、最后调用用户的main()函数。

4、可以不使用C库初始化函数__main()直接调用用户的main()【或别的定义!】,这个可以google一下。


;// <h> Stack Configuration
;//   <o> Stack Size (in Bytes) <0x0-0xFFFFFFFF:8>
;// </h>
Stack_Size      EQU     0x00000200                           ;//定义堆栈大小
                AREA    STACK, NOINIT, READWRITE, ALIGN=3    ;//定义一个数据段 按8字节对齐
Stack_Mem       SPACE   Stack_Size                           ;//保留Stack_Size大小的堆栈空间
__initial_sp                                                 ;//标号,代表堆栈顶部地址,后面有用

;// <h> Heap Configuration
;//   <o>  Heap Size (in Bytes) <0x0-0xFFFFFFFF:8>
;// </h>
Heap_Size       EQU     0x00000020                            ;//定义堆空间大小
                AREA    HEAP, NOINIT, READWRITE, ALIGN=3      ;//定义一个数据段,8字节对齐
__heap_base
Heap_Mem        SPACE   Heap_Size                             ;//保留Heap_Size的堆空间
__heap_limit                                                  ;//标号,代表堆末尾地址,后面有用

                PRESERVE8                                     ;//指示编译器8字节对齐
                THUMB                                         ;//指示编译器为THUMB指令

; Vector Table Mapped to Address 0 at Reset
                AREA    RESET, DATA, READONLY                  ;//定义只读数据段,其实放在CODE区,位于0地址
                
                EXTERN  NMIException
                EXTERN  HardFaultException
                EXTERN  MemManageException
                EXTERN  BusFaultException
                EXTERN  UsageFaultException
                EXTERN  SVCHandler
                EXTERN  DebugMonitor
                EXTERN  PendSVC
                EXTERN  SysTickHandler                         ;//声明这些符号在外部定义,同C
				                                               ;//在××it.c中实现这些函数 ,中断就能自动调用了
                EXPORT  __Vectors
__Vectors       DCD     __initial_sp              ; Top of Stack         //Cotex-M  要求此处为堆栈顶部地址
                DCD     Reset_Handler             ; Reset Handler
                DCD     NMIException              ; NMI Handler
                DCD     HardFaultException        ; Hard Fault Handler
                DCD     MemManageException        ; MPU Fault Handler
                DCD     BusFaultException         ; Bus Fault Handler
                DCD     UsageFaultException       ; Usage Fault Handler
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     0                         ; Reserved
                DCD     SVCHandler                ; SVCall Handler
                DCD     DebugMonitor              ; Debug Monitor Handler
                DCD     0                         ; Reserved
                DCD     PendSVC                   ; PendSV Handler
                DCD     SysTickHandler            ; SysTick Handler      //一大堆的异常处理函数地址
                ; External Interrupts
                EXTERN  WWDG_IRQHandler
                EXTERN  PVD_IRQHandler
                EXTERN  TAMPER_IRQHandler
                EXTERN  RTC_IRQHandler
                EXTERN  FLASH_IRQHandler
                EXTERN  RCC_IRQHandler
                EXTERN  EXTI0_IRQHandler
                EXTERN  EXTI1_IRQHandler
                EXTERN  EXTI2_IRQHandler
                EXTERN  EXTI3_IRQHandler
                EXTERN  EXTI4_IRQHandler
                EXTERN  DMAChannel1_IRQHandler
                EXTERN  DMAChannel2_IRQHandler
                EXTERN  DMAChannel3_IRQHandler
                EXTERN  DMAChannel4_IRQHandler
                EXTERN  DMAChannel5_IRQHandler
                EXTERN  DMAChannel6_IRQHandler
                EXTERN  DMAChannel7_IRQHandler
                EXTERN  ADC_IRQHandler
                EXTERN  USB_HP_CAN_TX_IRQHandler
                EXTERN  USB_LP_CAN_RX0_IRQHandler
                EXTERN  CAN_RX1_IRQHandler
                EXTERN  CAN_SCE_IRQHandler
                EXTERN  EXTI9_5_IRQHandler
                EXTERN  TIM1_BRK_IRQHandler
                EXTERN  TIM1_UP_IRQHandler
                EXTERN  TIM1_TRG_COM_IRQHandler
                EXTERN  TIM1_CC_IRQHandler
                EXTERN  TIM2_IRQHandler
                EXTERN  TIM3_IRQHandler
                EXTERN  TIM4_IRQHandler
                EXTERN  I2C1_EV_IRQHandler
                EXTERN  I2C1_ER_IRQHandler
                EXTERN  I2C2_EV_IRQHandler
                EXTERN  I2C2_ER_IRQHandler
                EXTERN  SPI1_IRQHandler
                EXTERN  SPI2_IRQHandler
                EXTERN  USART1_IRQHandler
                EXTERN  USART2_IRQHandler
                EXTERN  USART3_IRQHandler
                EXTERN  EXTI15_10_IRQHandler
                EXTERN  RTCAlarm_IRQHandler
                EXTERN  USBWakeUp_IRQHandler                    ;//同上,
                
                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   ;//同上

                AREA    |.text|, CODE, READONLY        ;//定义代码段

; Reset Handler
Reset_Handler   PROC                                        ;//Rset_Handler的实现
                EXPORT  Reset_Handler             [WEAK]    ;//在外部没有定义该符号时导出该符号,见HELP中[WEAK]
                IMPORT  __main                              ;//导入符号,__main为 运行时库提供的函数;完成堆栈,堆的初始话
                LDR     R0, =__main                         ;//等工作,会调用下面定义的__user_initial_stackheap;
                BX      R0                                  ;//跳到__main,进入C的世界
                ENDP

                ALIGN

; User Initial Stack & Heap
                IF      :DEF:__MICROLIB                     ;//如果使用micro lib,micro lib 描述见armlib.chm
                
                EXPORT  __initial_sp
                EXPORT  __heap_base
                EXPORT  __heap_limit                        ;//只导出几个定义
                
                ELSE                                        ;//如果使用默认C运行时库
                
                IMPORT  __use_two_region_memory
                EXPORT  __user_initial_stackheap
__user_initial_stackheap                                    ;//则进行堆栈和堆的赋值,在__main函数执行过程中调用。
                LDR     R0, =  Heap_Mem
                LDR     R1, =(Stack_Mem + Stack_Size)
                LDR     R2, = (Heap_Mem +  Heap_Size)
                LDR     R3, = Stack_Mem
                BX      LR
                ALIGN
                ENDIF

                END                                         ;//OK ,完了





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