STM32 keil mdk启动代码发分析 .

学习STM32,看了一堆乱七八糟的文档，准备写程序了，先分析了下STM32的启动代码，看着这堆鬼鬼的汇编代码，挺吓人的，看看帮助，查查网路，还是不那么难懂。

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;// <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