STM32啟動代碼分析

（1）按啟動代碼的次序，先看堆和棧的初始化：

Stack_Size EQU 0x00000200 ；定義Stack_Size為0x00000200

AREA STACK, NOINIT, READWRITE, ALIGN=3 ；定義棧，可初始為0，8字節(jié)對齊
Stack_Mem SPACE Stack_Size ；分配0x200個(gè)連續(xù)字節(jié)，并初始化為0
__initial_sp ；匯編代碼地址標(biāo)號

Heap_Size EQU 0x00000000

AREA HEAP, NOINIT, READWRITE, ALIGN=3
__heap_base
Heap_Mem SPACE Heap_Size
__heap_limit

PRESERVE8；指定當(dāng)前文件堆棧8字節(jié)對齊
THUMB ；告訴匯編器下面是32為的Thumb指令，如果需要匯編器將插入位以保證對齊

（2）中斷向量表定義

AREA RESET, DATA, READONLY ;定義復(fù)位向量段，只讀
EXPORT __Vectors ；定義一個(gè)可以在其他文件中使用的全局標(biāo)號。此處表示中斷地址

__Vectors DCD __initial_sp ;給__initial_sp分配4字節(jié)32位的地址0x0
DCD Reset_Handler ; 給標(biāo)號Reset Handler分配地址為0x00000004
DCD NMI_Handler ; 給標(biāo)號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 0 ;這種形式就是保留地址，不給任何標(biāo)號分配
DCD 0 ; Reserved
DCD 0 ; Reserved
DCD 0 ; Reserved
DCD SVC_Handler ; SVCall Handler
DCD DebugMon_Handler ; Debug Monitor Handler
DCD 0 ; 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）中斷向量表的轉(zhuǎn)移

AREA |.text|, CODE, READONLY ；代碼段定義

; Reset Handler

Reset_Handler PROC；標(biāo)記一個(gè)函數(shù)的開始
EXPORT Reset_Handler [WEAK]；[WEAK] 選項(xiàng)表示當(dāng)所有的源文件都沒有 定義這樣一個(gè)標(biāo)號時(shí)，編譯器也不給出錯(cuò)誤信息，在多數(shù)情況下將該標(biāo)號置為 0 ，若該標(biāo)號為 B 或 BL 指令引用，則將 B 或 BL指令置為 NOP 操作。EXPORT提示編譯器該標(biāo)號可以為外部文件引用。
IMPORT __main ;通知編譯器要使用的標(biāo)號在其他文件
LDR R0, =__main；使用“=”表示LDR目前是偽指令不是標(biāo)準(zhǔn)指令。這里是把__main的地址給RO。
BX R0；BX是ARM指令集和THUMB指令集之間程序的跳轉(zhuǎn)
ENDP

; Dummy Exception Handlers (infinite loops which can be modified)

NMI_Handler m;"m"其實(shí)就是PROC表示匯編函數(shù)的開始
EXPORT NMI_Handler [WEAK]
B .
ENDP
HardFault_Handler ;""是換行的意思
PROC
EXPORT HardFault_Handler [WEAK]
B . ;"."號到底是什么含義呢，目前還沒查到資料?？赡苁潜Ａ舻刂?，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）堆和棧的初始化

IF :DEF:__MICROLIB ；“DEF”的用法——:DEF:X 就是說X定義了則為真，否則為假

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