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。

;// Stack Configuration ;// Stack Size (in Bytes) <0x0-0xFFFFFFFF:8> ;// 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 ;// Heap Configuration ;// Heap Size (in Bytes) <0x0-0xFFFFFFFF:8> ;// 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