转自: http://www.it610.com/article/4037334.htm
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。
- ;// <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