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单片机启动过程是怎样的？

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答案对人有帮助，有参考价值 0 [cpp] view plain copy / **************************************************************************** * @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 _*ss / 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, =_ss ;从存储器中将_ss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 0 .word 0 .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 0 .word 0 .word 0 .word 0 .word 0 .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

2021-11-30 14:14:34 评论举报张奥