STM32系统时钟配置

只看该作者 · 2023-10-28 01:00

STM32启动后的第一步对于开发者来说就是系统时钟（RCC）的配置了,STM32系统默认用户外接8M晶振，经过倍频后，系统可以跑到72M。时钟的配置过程或者是初始化过程（当用户不配置时，使用默认外接8M晶振的配置）大体是这样的：
1、在STM32启动文件startup_stm32f10x_md.s的汇编代码中调用SystemInit()函数，而此函数是在system_stm32f10x.c文件中定义的；

注：如果用keil的启动文件，可能不会调用SystemInit()函数，需要自己在程序中调用。

startup_stm32f10x_md.s：

只看该作者 · 2023-10-28 01:00

2、在SystemInit()函数中通过对相关寄存器的一系列配置后，调用了本文件（system_stm32f10x.c）中的SetSysClock()函数

system_stm32f10x.c：

复制

/**

  * [url=home.php?mod=space&uid=247401]@brief[/url]  Setup the microcontroller system

  *         Initialize the Embedded Flash Interface, the PLL and update the 

  *         SystemCoreClock variable.

  * [url=home.php?mod=space&uid=536309]@NOTE[/url]   This function should be used only after reset.

  * @param  None

  * @retval None

  */

void SystemInit (void)

{

    //...省略一部分内容

#if defined (STM32F10X_HD) || (defined STM32F10X_XL) || (defined STM32F10X_HD_VL)

  #ifdef DATA_IN_ExtSRAM

    SystemInit_ExtMemCtl(); 

  #endif /* DATA_IN_ExtSRAM */

#endif 

 

  /* Configure the System clock frequency, HCLK, PCLK2 and PCLK1 prescalers */

  /* Configure the Flash Latency cycles and enable prefetch buffer */

  SetSysClock();

 

#ifdef VECT_TAB_SRAM

  SCB->VTOR = SRAM_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal SRAM. */

#else

  SCB->VTOR = FLASH_BASE | VECT_TAB_OFFSET; /* Vector Table Relocation in Internal FLASH. */

#endif 

}

只看该作者 · 2023-10-28 01:01

SetSysClock:、

只看该作者 · 2023-10-28 01:01

在此函数中通过判断之前定义过的宏，来决定调用设置系统不同时钟频率的函数，而这些宏是在此文件前面根据STM32不同的产品来定义的（对于低、中、高密度的产品使用外部8M晶振，对于互联型产品使用外部25M晶振），当然用户可以指定系统运行的速度24M、36M、48M、56M、72M，或自定义HSE_VALUE值，系统默认使用72M；

只看该作者 · 2023-10-28 01:01

只看该作者 · 2023-10-28 01:01

据第2步所述，系统将在SetSysClock()函数中调用SetSysClockTo72()函数，在SetSysClockTo72()函数中通过一系列对相关寄存器的配置，来完成系统时钟的配置。

只看该作者 · 2023-10-28 01:02

SetSysClockTo72:

复制

/**

  * @brief  Sets System clock frequency to 72MHz and configure HCLK, PCLK2 

  *         and PCLK1 prescalers. 

  * @note   This function should be used only after reset.

  * @param  None

  * @retval None

  */

static void SetSysClockTo72(void)

{

  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;

  

  /* SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/    

  /* Enable HSE */    

  RCC->CR |= ((uint32_t)RCC_CR_HSEON);

 

  /* Wait till HSE is ready and if Time out is reached exit */

  do

  {

    HSEStatus = RCC->CR & RCC_CR_HSERDY;

    StartUpCounter++;  

  } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

 

  if ((RCC->CR & RCC_CR_HSERDY) != RESET)

  {

    HSEStatus = (uint32_t)0x01;

  }

  else

  {

    HSEStatus = (uint32_t)0x00;

  }  

 

  if (HSEStatus == (uint32_t)0x01)

  {

    /* Enable Prefetch Buffer */

    FLASH->ACR |= FLASH_ACR_PRFTBE;

 

    /* Flash 2 wait state */

    FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);

    FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_2;    

 

 

    /* HCLK = SYSCLK */

    RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;

      

    /* PCLK2 = HCLK */

    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;

    

    /* PCLK1 = HCLK */

    RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV2;

 

#ifdef STM32F10X_CL

    /* Configure PLLs ------------------------------------------------------*/

    /* PLL2 configuration: PLL2CLK = (HSE / 5) * 8 = 40 MHz */

    /* PREDIV1 configuration: PREDIV1CLK = PLL2 / 5 = 8 MHz */

        

    RCC->CFGR2 &= (uint32_t)~(RCC_CFGR2_PREDIV2 | RCC_CFGR2_PLL2MUL |

                              RCC_CFGR2_PREDIV1 | RCC_CFGR2_PREDIV1SRC);

    RCC->CFGR2 |= (uint32_t)(RCC_CFGR2_PREDIV2_DIV5 | RCC_CFGR2_PLL2MUL8 |

                             RCC_CFGR2_PREDIV1SRC_PLL2 | RCC_CFGR2_PREDIV1_DIV5);

  

    /* Enable PLL2 */

    RCC->CR |= RCC_CR_PLL2ON;

    /* Wait till PLL2 is ready */

    while((RCC->CR & RCC_CR_PLL2RDY) == 0)

    {

    }

    

   

    /* PLL configuration: PLLCLK = PREDIV1 * 9 = 72 MHz */ 

    RCC->CFGR &= (uint32_t)~(RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLSRC | RCC_CFGR_PLLMULL);

    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLXTPRE_PREDIV1 | RCC_CFGR_PLLSRC_PREDIV1 | 

                            RCC_CFGR_PLLMULL9); 

#else    

    /*  PLL configuration: PLLCLK = HSE * 9 = 72 MHz */

    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE |

                                        RCC_CFGR_PLLMULL));

    RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSE | RCC_CFGR_PLLMULL9);

#endif /* STM32F10X_CL */

 

    /* Enable PLL */

    RCC->CR |= RCC_CR_PLLON;

 

    /* Wait till PLL is ready */

    while((RCC->CR & RCC_CR_PLLRDY) == 0)

    {

    }

    

    /* Select PLL as system clock source */

    RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));

    RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;    

 

    /* Wait till PLL is used as system clock source */

    while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)0x08)

    {

    }

  }

  else

  { /* If HSE fails to start-up, the application will have wrong clock 

         configuration. User can add here some code to deal with this error */

  }

}

只看该作者 · 2023-10-28 01:02

/**
  * @brief  Sets System clock frequency to 72MHz and configure HCLK, PCLK2
  *       and PCLK1 prescalers.
  * @note This function should be used only after reset.
  * @param  None
  * @retval None
  */
static void SetSysClockTo72(void)
{
  __IO uint32_t StartUpCounter = 0, HSEStatus = 0;

  /* SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/
  /* Enable HSE */
  RCC->CR |= ((uint32_t)RCC_CR_HSEON);

  /* Wait till HSE is ready and if Time out is reached exit */
  do
  {
HSEStatus = RCC->CR & RCC_CR_HSERDY;
StartUpCounter++;
  } while((HSEStatus == 0) && (StartUpCounter != HSE_STARTUP_TIMEOUT));

  if ((RCC->CR & RCC_CR_HSERDY) != RESET)
  {
HSEStatus = (uint32_t)0x01;
  }
  else
  {
HSEStatus = (uint32_t)0x00;
  }

  if (HSEStatus == (uint32_t)0x01)
  {
/* Enable Prefetch Buffer */
FLASH->ACR |= FLASH_ACR_PRFTBE;

/* Flash 2 wait state */
FLASH->ACR &= (uint32_t)((uint32_t)~FLASH_ACR_LATENCY);
FLASH->ACR |= (uint32_t)FLASH_ACR_LATENCY_2;

/* HCLK = SYSCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_HPRE_DIV1;

/* PCLK2 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE2_DIV1;

/* PCLK1 = HCLK */
RCC->CFGR |= (uint32_t)RCC_CFGR_PPRE1_DIV2;

#ifdef STM32F10X_CL
/* Configure PLLs ------------------------------------------------------*/
/* PLL2 configuration: PLL2CLK = (HSE / 5) * 8 = 40 MHz */
/* PREDIV1 configuration: PREDIV1CLK = PLL2 / 5 = 8 MHz */

RCC->CFGR2 &= (uint32_t)~(RCC_CFGR2_PREDIV2 | RCC_CFGR2_PLL2MUL |
                           RCC_CFGR2_PREDIV1 | RCC_CFGR2_PREDIV1SRC);
RCC->CFGR2 |= (uint32_t)(RCC_CFGR2_PREDIV2_DIV5 | RCC_CFGR2_PLL2MUL8 |
                           RCC_CFGR2_PREDIV1SRC_PLL2 | RCC_CFGR2_PREDIV1_DIV5);

/* Enable PLL2 */
RCC->CR |= RCC_CR_PLL2ON;
/* Wait till PLL2 is ready */
while((RCC->CR & RCC_CR_PLL2RDY) == 0)
{
}

/* PLL configuration: PLLCLK = PREDIV1 * 9 = 72 MHz */
RCC->CFGR &= (uint32_t)~(RCC_CFGR_PLLXTPRE | RCC_CFGR_PLLSRC | RCC_CFGR_PLLMULL);
RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLXTPRE_PREDIV1 | RCC_CFGR_PLLSRC_PREDIV1 |
                        RCC_CFGR_PLLMULL9);
#else
/*  PLL configuration: PLLCLK = HSE * 9 = 72 MHz */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_PLLSRC | RCC_CFGR_PLLXTPRE |
                                    RCC_CFGR_PLLMULL));
RCC->CFGR |= (uint32_t)(RCC_CFGR_PLLSRC_HSE | RCC_CFGR_PLLMULL9);
#endif /* STM32F10X_CL */

/* Enable PLL */
RCC->CR |= RCC_CR_PLLON;

/* Wait till PLL is ready */
while((RCC->CR & RCC_CR_PLLRDY) == 0)
{
}

/* Select PLL as system clock source */
RCC->CFGR &= (uint32_t)((uint32_t)~(RCC_CFGR_SW));
RCC->CFGR |= (uint32_t)RCC_CFGR_SW_PLL;

/* Wait till PLL is used as system clock source */
while ((RCC->CFGR & (uint32_t)RCC_CFGR_SWS) != (uint32_t)0x08)
{
}
  }
  else
  { /* If HSE fails to start-up, the application will have wrong clock
      configuration. User can add here some code to deal with this error */
  }
}

只看该作者 · 2023-10-28 01:02

备注：
启动文件：
startup_stm32f10x_cl.s 互联型的器件，STM32F105xx，STM32F107xx
startup_stm32f10x_hd.s 大容量的STM32F101xx，STM32F102xx，STM32F103xx
startup_stm32f10x_hd_vl.s 大容量的STM32F100xx
startup_stm32f10x_ld.s 小容量的STM32F101xx，STM32F102xx，STM32F103xx
startup_stm32f10x_ld_vl.s 小容量的STM32F100xx
startup_stm32f10x_md.s 中容量的STM32F101xx，STM32F102xx，STM32F103xx
startup_stm32f10x_md_vl.s 中容量的STM32F100xx
startup_stm32f10x_xl.s FLASH在512K到1024K字节的STM32F101xx，STM32F102xx，STM32F103xx

只看该作者 · 2023-10-28 01:02

产品分类：
- Low-density Value line devices are STM32F100xx microcontrollers where the
Flash memory density ranges between 16 and 32 Kbytes.
- Low-density devices are STM32F101xx, STM32F102xx and STM32F103xx
microcontrollers where the Flash memory density ranges between 16 and 32 Kbytes.
- Medium-density Value line devices are STM32F100xx microcontrollers where
the Flash memory density ranges between 64 and 128 Kbytes.
- Medium-density devices are STM32F101xx, STM32F102xx and STM32F103xx
microcontrollers where the Flash memory density ranges between 64 and 128 Kbytes.
- High-density devices are STM32F101xx and STM32F103xx microcontrollers where
the Flash memory density ranges between 256 and 512 Kbytes.
- XL-density devices are STM32F101xx and STM32F103xx microcontrollers where
the Flash memory density ranges between 512 and 1024 Kbytes.
- Connectivity line devices are STM32F105xx and STM32F107xx microcontrollers.

只看该作者 · 2023-12-10 07:04

具存储功能的存储器芯片也能加密

只看该作者 · 2023-12-10 08:07

紫外光复位保护电路是不行的

只看该作者 · 2023-12-10 10:03

大部分能够读取或者识别Flash上的数据就能够获得Firmware文件

只看该作者 · 2023-12-10 11:06

微探针技术都属于侵入型攻击

只看该作者 · 2023-12-10 13:02

如果在编程时加密锁定位被使能/锁定，就无法用普通编程器直接读取单片机内的程序

只看该作者 · 2023-12-10 14:05

编程器定位插字节

只看该作者 · 2023-12-10 15:08

单片机一般都有内部程序区和数据区

只看该作者 · 2023-12-10 16:01

缩短距离较近的电容的寿命

只看该作者 · 2023-12-10 17:04

利用协议、加密算法或这些算法中的安全漏洞来进行攻击

只看该作者 · 2023-12-10 18:07

CPLD解密，DSP解密都习惯称为单片机解密