启动代码在芯片上还是很重要的一部分，我们以F4的启动代码为例
下面启动代码里的汇编的注释已经去掉，添加的注释用 // 表示
/****************************************************************************/
0.分号“；”后的内容相当于C程序中的注释
1.标号的作用：标号必须顶格写，让汇编器计算程序转移的地址
2.伪指令
EQU 用于定义常数
LDR 被汇编器转换成一条“相对PC的加载指令”
BLX 转移到后面代表的地址
BX 转移到后面的地址
PROC，ENDP 表示一段程序的开始和结束
/****************************************************************************/
Stack_Size EQU 0x00000400
AREA STACK, NOINIT, READWRITE, ALIGN=3 //定义一段叫STACK的数据段，并初始化为0，可读可写，以8字节对齐
Stack_Mem SPACE Stack_Size //开辟一个大小为1KB（0x0000400，以字节为单位）的内存空间命名为Stack_Mem
__initial_sp //__initial_sp是一个标号，在这里相当于栈顶地址
Heap_Size EQU 0x00000200
AREA HEAP, NOINIT, READWRITE, ALIGN=3 //定义一段HEAP数据段，不初始化为0，可读可写，8字节对齐
__heap_base //堆的基地址
Heap_Mem SPACE Heap_Size //开辟一段0.5KB的空间，命名为Heap_Mem
__heap_limit //堆的结束地址
PRESERVE8 //表示当前文件中的堆栈空间以8字节对齐
THUMB //使用YHUMB指令
AREA RESET, DATA, READONLY //开辟一段数据段，只读，命名为RESET
EXPORT __Vectors //EXPORT表示可被外部调用
EXPORT __Vectors_End
EXPORT __Vectors_Size
__Vectors DCD __initial_sp ; Top of Stack //DCD表示分配一个四字节的空间
DCD Reset_Handler ; Reset Handler
DCD NMI_Handler ; NMI Handler
DCD HardFault_Handler ; Hard Fault Handler
.
. //中间部分省略，这一段定义的是中断向量表
.
DCD DCMI_IRQHandler ; DCMI
DCD CRYP_IRQHandler ; CRYP crypto
DCD HASH_RNG_IRQHandler ; Hash and Rng
DCD FPU_IRQHandler ; FPU
__Vectors_End
__Vectors_Size EQU __Vectors_End - __Vectors //向量表的大小为最后的地址减去开始的地址，为188字节
AREA |.text|, CODE, READONLY //定义一段代码段，只读
Reset_Handler PROC //这一段定义复位中断服务函数
EXPORT Reset_Handler [WEAK] //[WEAK]为弱定义，表示如果在该文件外还有和这个相同的标号，则优先执行外部的，这样我们的中断服务函数就可以在文件中的任意位置放置
IMPORT SystemInit //IMPORT表示从外部引用 SystemInit（在system_stm32f4文件内）
IMPORT __main //__main为C库中的函数，会完成一系列的配置，最终调用用户写的main函数
LDR R0, =SystemInit //将SystemInit地址加载到R0寄存器
BLX R0 //相当于执行上面加载的函数
LDR R0, =__main //将__main地址加载到R0寄存器
BX R0 //执行上面加载的函数
ENDP
; Dummy Exception Handlers (infinite loops which can be modified)
NMI_Handler PROC //NMI_Handler为不可屏蔽中断
EXPORT NMI_Handler [WEAK]
B . //如果这个中断服务函数在外部没有定义，就会进入启动文件默认的中断服务函数B . 表示死循环，
ENDP //可以用仿真器实际操作一下，下面的和这里的一样
HardFault_Handler\
PROC
EXPORT HardFault_Handler [WEAK]
B .
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 TAMP_STAMP_IRQHandler [WEAK]
EXPORT RTC_WKUP_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 DMA1_Stream0_IRQHandler [WEAK]
EXPORT DMA1_Stream1_IRQHandler [WEAK]
EXPORT DMA1_Stream2_IRQHandler [WEAK]
EXPORT DMA1_Stream3_IRQHandler [WEAK]
EXPORT DMA1_Stream4_IRQHandler [WEAK]
EXPORT DMA1_Stream5_IRQHandler [WEAK]
EXPORT DMA1_Stream6_IRQHandler [WEAK]
EXPORT ADC_IRQHandler [WEAK]
EXPORT CAN1_TX_IRQHandler [WEAK]
EXPORT CAN1_RX0_IRQHandler [WEAK]
EXPORT CAN1_RX1_IRQHandler [WEAK]
EXPORT CAN1_SCE_IRQHandler [WEAK]
EXPORT EXTI9_5_IRQHandler [WEAK]
EXPORT TIM1_BRK_TIM9_IRQHandler [WEAK]
EXPORT TIM1_UP_TIM10_IRQHandler [WEAK]
EXPORT TIM1_TRG_COM_TIM11_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 RTC_Alarm_IRQHandler [WEAK]
EXPORT OTG_FS_WKUP_IRQHandler [WEAK]
EXPORT TIM8_BRK_TIM12_IRQHandler [WEAK]
EXPORT TIM8_UP_TIM13_IRQHandler [WEAK]
EXPORT TIM8_TRG_COM_TIM14_IRQHandler [WEAK]
EXPORT TIM8_CC_IRQHandler [WEAK]
EXPORT DMA1_Stream7_IRQHandler [WEAK]
EXPORT FSMC_IRQHandler [WEAK]
EXPORT SDIO_IRQHandler [WEAK]
EXPORT TIM5_IRQHandler [WEAK]
EXPORT SPI3_IRQHandler [WEAK]
EXPORT UART4_IRQHandler [WEAK]
EXPORT UART5_IRQHandler [WEAK]
EXPORT TIM6_DAC_IRQHandler [WEAK]
EXPORT TIM7_IRQHandler [WEAK]
EXPORT DMA2_Stream0_IRQHandler [WEAK]
EXPORT DMA2_Stream1_IRQHandler [WEAK]
EXPORT DMA2_Stream2_IRQHandler [WEAK]
EXPORT DMA2_Stream3_IRQHandler [WEAK]
EXPORT DMA2_Stream4_IRQHandler [WEAK]
EXPORT ETH_IRQHandler [WEAK]
EXPORT ETH_WKUP_IRQHandler [WEAK]
EXPORT CAN2_TX_IRQHandler [WEAK]
EXPORT CAN2_RX0_IRQHandler [WEAK]
EXPORT CAN2_RX1_IRQHandler [WEAK]
EXPORT CAN2_SCE_IRQHandler [WEAK]
EXPORT OTG_FS_IRQHandler [WEAK]
EXPORT DMA2_Stream5_IRQHandler [WEAK]
EXPORT DMA2_Stream6_IRQHandler [WEAK]
EXPORT DMA2_Stream7_IRQHandler [WEAK]
EXPORT USART6_IRQHandler [WEAK]
EXPORT I2C3_EV_IRQHandler [WEAK]
EXPORT I2C3_ER_IRQHandler [WEAK]
EXPORT OTG_HS_EP1_OUT_IRQHandler [WEAK]
EXPORT OTG_HS_EP1_IN_IRQHandler [WEAK]
EXPORT OTG_HS_WKUP_IRQHandler [WEAK]
EXPORT OTG_HS_IRQHandler [WEAK]
EXPORT DCMI_IRQHandler [WEAK]
EXPORT CRYP_IRQHandler [WEAK]
EXPORT HASH_RNG_IRQHandler [WEAK]
EXPORT FPU_IRQHandler [WEAK]
WWDG_IRQHandler
PVD_IRQHandler
TAMP_STAMP_IRQHandler
RTC_WKUP_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMA1_Stream0_IRQHandler
DMA1_Stream1_IRQHandler
DMA1_Stream2_IRQHandler
DMA1_Stream3_IRQHandler
DMA1_Stream4_IRQHandler
DMA1_Stream5_IRQHandler
DMA1_Stream6_IRQHandler
ADC_IRQHandler
CAN1_TX_IRQHandler
CAN1_RX0_IRQHandler
CAN1_RX1_IRQHandler
CAN1_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_TIM9_IRQHandler
TIM1_UP_TIM10_IRQHandler
TIM1_TRG_COM_TIM11_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
RTC_Alarm_IRQHandler
OTG_FS_WKUP_IRQHandler
TIM8_BRK_TIM12_IRQHandler
TIM8_UP_TIM13_IRQHandler
TIM8_TRG_COM_TIM14_IRQHandler
TIM8_CC_IRQHandler
DMA1_Stream7_IRQHandler
FSMC_IRQHandler
SDIO_IRQHandler
TIM5_IRQHandler
SPI3_IRQHandler
UART4_IRQHandler
UART5_IRQHandler
TIM6_DAC_IRQHandler
TIM7_IRQHandler
DMA2_Stream0_IRQHandler
DMA2_Stream1_IRQHandler
DMA2_Stream2_IRQHandler
DMA2_Stream3_IRQHandler
DMA2_Stream4_IRQHandler
ETH_IRQHandler
ETH_WKUP_IRQHandler
CAN2_TX_IRQHandler
CAN2_RX0_IRQHandler
CAN2_RX1_IRQHandler
CAN2_SCE_IRQHandler
OTG_FS_IRQHandler
DMA2_Stream5_IRQHandler
DMA2_Stream6_IRQHandler
DMA2_Stream7_IRQHandler
USART6_IRQHandler
I2C3_EV_IRQHandler
I2C3_ER_IRQHandler
OTG_HS_EP1_OUT_IRQHandler
OTG_HS_EP1_IN_IRQHandler
OTG_HS_WKUP_IRQHandler
OTG_HS_IRQHandler
DCMI_IRQHandler
CRYP_IRQHandler
HASH_RNG_IRQHandler
FPU_IRQHandler
B .
ENDP
ALIGN
;*******************************************************************************
; User Stack and Heap initialization
;*******************************************************************************
IF :DEF:__MICROLIB //这边判断是否使用微库
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 //分别将分别将栈顶地址，栈底地址，堆顶地址及堆基地址存放在寄存器R1，R3，R0，R2中。
LDR R1, =(Stack_Mem + Stack_Size)
LDR R2, = (Heap_Mem + Heap_Size)
LDR R3, = Stack_Mem
BX LR
ALIGN
ENDIF
END
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