中容量STM32处理器启动代码的理解

2019-03-24 来源：eefocus

今天要介绍一下STM32的启动代码，我这里使用的是中容量的STM32f103c8t6,对应的启动文件就是startup_stm32f10x_md.s，我这里启动文件版本是V3.6.2

不多说废话，先上我注释过的源码：

/**

******************************************************************************

* @file startup_stm32f10x_md.s

* @author MCD Application Team

* @version V3.6.2

* @date 28-February-2013

* @brief STM32F10x Medium Density Devices vector table for RIDE7 toolchain.

* This module performs:

* - Set the initial SP -设置最初的SP寄存器值

* - Set the initial PC == Reset_Handler, -设置最初的PC寄存器值 == Reset_Handler

* - Set the vector table entries with the exceptions ISR address -在有特殊的ISR(中断服务程序)地址的情况下设置向量表入口

* - Configure the clock system -设置时钟系统

* - Branches to main in the C library (which eventually -C库文件中由分支到主函数（最后调用了主函数）

* calls main()).

* After Reset the Cortex-M3 processor is in Thread mode, 在线程模式下复位了CM3处理器后，此时优先级特权化，栈顶设置为主函数

* priority is Privileged, and the Stack is set to Main.

******************************************************************************

* @attention

© COPYRIGHT 2013 STMicroelectronics

* Licensed under MCD-ST Liberty SW License Agreement V2, (the 'License');

* You may not use this file except in compliance with the License.

* You may obtain a copy of the License at:

* http://www.st.com/software_license_agreement_liberty_v2

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an 'AS IS' BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

******************************************************************************

.syntax unified ;表示使用了统一汇编语言语法

.cpu cortex-m3 ;MCU为CM3

.fpu softvfp

.thumb ;指令集

.global g_pfnVectors ;global使得g_pfnVectors可以被其他目标文件使用

.global Default_Handler

/* start address for the initialization values of the .data section. 初始化.data 块的起始地址，这个地址在链接脚本中被定义

defined in linker script */

.word _sidata

/* start address for the .data section. defined in linker script .data块的起始地址，这个地址在链接脚本中被定义*/

.word _sdata

/* end address for the .data section. defined in linker script .data块的结束地址，这个地址在链接脚本中被定义*/

.word _edata

/* start address for the .bss section. defined in linker script .bss块的起始地址，这个地址在链接脚本中被定义*/

.word _sbss

/* end address for the .bss section. defined in linker script .bss块的结束地址，这个地址在链接脚本中被定义*/

.word _ebss

.equ BootRAM, 0xF108F85F /*这里跟c中的宏定义类似，即BootRAM = 0xF108F85F,不参与编译*/

/**

* @brief This is the code that gets called when the processor first

* starts execution following a reset event. Only the absolutely

* necessary set is performed, after which the application

* supplied main() routine is called.

* @param None

* @retval : None

.section .text.Reset_Handler

.weak Reset_Handler

.type Reset_Handler, %function

Reset_Handler:

/* Copy the data segment initializers from flash to SRAM 将初始化了的数据段从flash复制到SRAM*/

movs r1, #0 ;将立即数0赋值给r1寄存器

b LoopCopyDataInit ;程序转移到LoopCopyDataInit处

CopyDataInit: ;从FLASH中拷贝地址在sdata和edata之间的代码到SRAM中

ldr r3, =_sidata ;从存储器中将_sidata加载到寄存器r3中

ldr r3, [r3, r1] ;从地址r3+r1处读取一个字（32bit）到r3中

str r3, [r0, r1] ;把寄存器r3的值存储到存储器中地址为r0+r1地址处

adds r1, r1, #4 ;r1 = r1 + 4

LoopCopyDataInit:

ldr r0, =_sdata ;从存储器中将_sidata加载到寄存器r0中

ldr r3, =_edata ;从存储器中将_edata加载到寄存器r3中

adds r2, r0, r1 ;r2=r0+r1

cmp r2, r3 ;计算r2 - r3,若小于0，标志位为0，反之为1

bcc CopyDataInit ;如果标志位为0（无借位）即r2

ldr r2, =_sbss ;从存储器中将_sbss加载到寄存器r2中

b LoopFillZerobss ;无条件跳转到LoopFillZerobss

/* Zero fill the bss segment. */

FillZerobss:

movs r3, #0 ;将立即数0存入寄存器r3

str r3, [r2], #4 ;将寄存器r3的值存储到地址为r2寄存器值得地址处后，r2 = r2 + 4

LoopFillZerobss:

ldr r3, = _ebss ;从存储器中将_ebss加载到寄存器r3中

cmp r2, r3 ;比较r2,r3，然后更新标志位

bcc FillZerobss ;如果标志位为0（无借位），则跳转到FillZerobss处

/* Call the clock system intitialization function.*/

/* bl SystemInit */

/* Call the application's entry point.*/

bl main ;转移到main函数起始处

bx lr ;转移到地址lr处

.size Reset_Handler, .-Reset_Handler ;相当于mov pc lr lr即寄存器r14

/**

* @brief This is the code that gets called when the processor receives an

* unexpected interrupt. This simply enters an infinite loop, preserving

* the system state for examination by a debugger.

* @param None

* @retval None

.section .text.Default_Handler,'ax',%progbits

Default_Handler:

Infinite_Loop:

b Infinite_Loop ;无条件跳转到Infinite_Loop

.size Default_Handler, .-Default_Handler

/******************************************************************************

* The minimal vector table for a Cortex M3. Note that the proper constructs Cortex M3的最小向量表

* must be placed on this to ensure that it ends up at physical address

* 0x0000.0000.

******************************************************************************/

.section .isr_vector,'a',%progbits ;定义中断向量表的数据段

.type g_pfnVectors, %object

.size g_pfnVectors, .-g_pfnVectors

g_pfnVectors:

.word _estack ;在当前位置放置一个word型的值，这个值为_estack；后面同理

.word Reset_Handler ;这一块程序的意思就是说以g_pfnVectors为初始地址，然后依次

.word NMI_Handler ;以字为单位写入相应的数据

.word HardFault_Handler

.word MemManage_Handler

.word BusFault_Handler

.word UsageFault_Handler

.word 0

.word SVC_Handler

.word DebugMon_Handler

.word 0

.word PendSV_Handler

.word SysTick_Handler

.word WWDG_IRQHandler

.word PVD_IRQHandler

.word TAMPER_IRQHandler

.word RTC_IRQHandler

.word FLASH_IRQHandler

.word RCC_IRQHandler

.word EXTI0_IRQHandler

.word EXTI1_IRQHandler

.word EXTI2_IRQHandler

.word EXTI3_IRQHandler

.word EXTI4_IRQHandler

.word DMA1_Channel1_IRQHandler

.word DMA1_Channel2_IRQHandler

.word DMA1_Channel3_IRQHandler

.word DMA1_Channel4_IRQHandler

.word DMA1_Channel5_IRQHandler

.word DMA1_Channel6_IRQHandler

.word DMA1_Channel7_IRQHandler

.word ADC1_2_IRQHandler

.word USB_HP_CAN1_TX_IRQHandler

.word USB_LP_CAN1_RX0_IRQHandler

.word CAN1_RX1_IRQHandler

.word CAN1_SCE_IRQHandler

.word EXTI9_5_IRQHandler

.word TIM1_BRK_IRQHandler

.word TIM1_UP_IRQHandler

.word TIM1_TRG_COM_IRQHandler

.word TIM1_CC_IRQHandler

.word TIM2_IRQHandler

.word TIM3_IRQHandler

.word TIM4_IRQHandler

.word I2C1_EV_IRQHandler

.word I2C1_ER_IRQHandler

.word I2C2_EV_IRQHandler

.word I2C2_ER_IRQHandler

.word SPI1_IRQHandler

.word SPI2_IRQHandler

.word USART1_IRQHandler

.word USART2_IRQHandler

.word USART3_IRQHandler

.word EXTI15_10_IRQHandler

.word RTCAlarm_IRQHandler

.word USBWakeUp_IRQHandler

.word 0

.word BootRAM /* @0x108. This is for boot in RAM mode for 这个是为stm32f10系列中容量系列设备的boot中的RAM模式准备的

STM32F10x Medium Density devices. */

/*******************************************************************************

* Provide weak aliases for each Exception handler to the Default_Handler.

* As they are weak aliases, any function with the same name will override

* this definition.

*******************************************************************************/

.weak NMI_Handler ;定义一个弱别名NMI_Handler

.thumb_set NMI_Handler,Default_Handler ;如果这个不重写这个弱别名，那么默认执行Default_Handler，反之这执行重写过的NMI_Handler

.weak HardFault_Handler

.thumb_set HardFault_Handler,Default_Handler

.weak MemManage_Handler

.thumb_set MemManage_Handler,Default_Handler

.weak BusFault_Handler

.thumb_set BusFault_Handler,Default_Handler

.weak UsageFault_Handler

.thumb_set UsageFault_Handler,Default_Handler

.weak SVC_Handler

.thumb_set SVC_Handler,Default_Handler

.weak DebugMon_Handler

.thumb_set DebugMon_Handler,Default_Handler

.weak PendSV_Handler

.thumb_set PendSV_Handler,Default_Handler

.weak SysTick_Handler

.thumb_set SysTick_Handler,Default_Handler

.weak WWDG_IRQHandler

.thumb_set WWDG_IRQHandler,Default_Handler

.weak PVD_IRQHandler

.thumb_set PVD_IRQHandler,Default_Handler

.weak TAMPER_IRQHandler

.thumb_set TAMPER_IRQHandler,Default_Handler

.weak RTC_IRQHandler

.thumb_set RTC_IRQHandler,Default_Handler

.weak FLASH_IRQHandler

.thumb_set FLASH_IRQHandler,Default_Handler

.weak RCC_IRQHandler

.thumb_set RCC_IRQHandler,Default_Handler

.weak EXTI0_IRQHandler

.thumb_set EXTI0_IRQHandler,Default_Handler

.weak EXTI1_IRQHandler

.thumb_set EXTI1_IRQHandler,Default_Handler

.weak EXTI2_IRQHandler

.thumb_set EXTI2_IRQHandler,Default_Handler

.weak EXTI3_IRQHandler

.thumb_set EXTI3_IRQHandler,Default_Handler

.weak EXTI4_IRQHandler

.thumb_set EXTI4_IRQHandler,Default_Handler

.weak DMA1_Channel1_IRQHandler

.thumb_set DMA1_Channel1_IRQHandler,Default_Handler

.weak DMA1_Channel2_IRQHandler

.thumb_set DMA1_Channel2_IRQHandler,Default_Handler

.weak DMA1_Channel3_IRQHandler

.thumb_set DMA1_Channel3_IRQHandler,Default_Handler

.weak DMA1_Channel4_IRQHandler

.thumb_set DMA1_Channel4_IRQHandler,Default_Handler

.weak DMA1_Channel5_IRQHandler

.thumb_set DMA1_Channel5_IRQHandler,Default_Handler

.weak DMA1_Channel6_IRQHandler

.thumb_set DMA1_Channel6_IRQHandler,Default_Handler

.weak DMA1_Channel7_IRQHandler

.thumb_set DMA1_Channel7_IRQHandler,Default_Handler

.weak ADC1_2_IRQHandler

.thumb_set ADC1_2_IRQHandler,Default_Handler

.weak USB_HP_CAN1_TX_IRQHandler

.thumb_set USB_HP_CAN1_TX_IRQHandler,Default_Handler

.weak USB_LP_CAN1_RX0_IRQHandler

.thumb_set USB_LP_CAN1_RX0_IRQHandler,Default_Handler

.weak CAN1_RX1_IRQHandler

.thumb_set CAN1_RX1_IRQHandler,Default_Handler

.weak CAN1_SCE_IRQHandler

.thumb_set CAN1_SCE_IRQHandler,Default_Handler

.weak EXTI9_5_IRQHandler

.thumb_set EXTI9_5_IRQHandler,Default_Handler

.weak TIM1_BRK_IRQHandler

.thumb_set TIM1_BRK_IRQHandler,Default_Handler

.weak TIM1_UP_IRQHandler

.thumb_set TIM1_UP_IRQHandler,Default_Handler

.weak TIM1_TRG_COM_IRQHandler

.thumb_set TIM1_TRG_COM_IRQHandler,Default_Handler

.weak TIM1_CC_IRQHandler

.thumb_set TIM1_CC_IRQHandler,Default_Handler

.weak TIM2_IRQHandler

.thumb_set TIM2_IRQHandler,Default_Handler

.weak TIM3_IRQHandler

.thumb_set TIM3_IRQHandler,Default_Handler

.weak TIM4_IRQHandler

.thumb_set TIM4_IRQHandler,Default_Handler

.weak I2C1_EV_IRQHandler

.thumb_set I2C1_EV_IRQHandler,Default_Handler

.weak I2C1_ER_IRQHandler

.thumb_set I2C1_ER_IRQHandler,Default_Handler

.weak I2C2_EV_IRQHandler

.thumb_set I2C2_EV_IRQHandler,Default_Handler

.weak I2C2_ER_IRQHandler

.thumb_set I2C2_ER_IRQHandler,Default_Handler

.weak SPI1_IRQHandler

.thumb_set SPI1_IRQHandler,Default_Handler

.weak SPI2_IRQHandler

.thumb_set SPI2_IRQHandler,Default_Handler

.weak USART1_IRQHandler

.thumb_set USART1_IRQHandler,Default_Handler

.weak USART2_IRQHandler

.thumb_set USART2_IRQHandler,Default_Handler

.weak USART3_IRQHandler

.thumb_set USART3_IRQHandler,Default_Handler

.weak EXTI15_10_IRQHandler

.thumb_set EXTI15_10_IRQHandler,Default_Handler

.weak RTCAlarm_IRQHandler

.thumb_set RTCAlarm_IRQHandler,Default_Handler

.weak USBWakeUp_IRQHandler

.thumb_set USBWakeUp_IRQHandler,Default_Handler

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

如果有注释不准确的地方还希望能够给我指出，感谢感谢~~

这里以STM32程序运行过程为轴线，依次介绍单片机启动过程中的流程。

在给单片机上电前，先通过给BOOT0和BOOT1连接高低电平来设置程序启动的初始位置。STM32程序启动的位置有三种：

1：Main Flash memory

是STM32内置的Flash，一般我们使用JTAG或者SWD模式下载程序时，就是下载到这个里面，重启后也直接从这启动程序。

2：System memory

从系统存储器启动，这种模式启动的程序功能是由厂家设置的。一般来说，这种启动方式用的比较少。

3：Embedded Memory

内置SRAM，既然是SRAM，自然也就没有程序存储的能力了，这个模式一般用于程序调试。

在这三种方式里面用的最多的是第一种，下面以第一种启动方式为例进行介绍：

在重启芯片时，SYSCLK的第4个上升沿，BOOT引脚的值将被锁存。然后进入启动文件，具体的启动文件为startup_stm32f10x_md.s。

首先启动文件中有一个Reset_Handler，这个汇编函数的作用有两个：

a.将FLASH中的程序代码拷贝到SRAM中

b.将系统堆栈初始化（清0）

然后进入main，从而进入c的世界。

但是启动文件到这里还没有结束，后面还有一个部分。

这个部分的作用是定义了一个段来存放中断向量表，然后以字的形式分别填入了中断的指针。

在这以后还有一个部分，后面这个部分的作用是给中断服务定义了一个弱别名，这个弱别名的作用就是在有中断被触发后，如果没有重写对应的弱别名，那么程序就默认执行默认的中断处理函数（Default_Handler），反之则执行重写了的中断处理函数

进入单片机查看更多内容>>

中容量 STM32 启动代码

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