STM32内部flash详解（1）-Toy模板网

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STM32 内部FLAsh概述

今天说一下STM32中的内部flash。
当我们把写好的代码下载MCU中，这个代码时存放在flash中的。当芯片重启复位上电后，会通过内核对flash进行代码的加载运行。大致是这个过程。

主要特性

flash读操作
flash编程/擦除操作
读写保护
I-Code 上的预取操作
I-Code 上的 64 个缓存（128 位宽）
D-Code 上的 8 个缓存（128 位宽）
128 位宽数据读取
字节、半字、字和双字数据写入
扇区擦除与全部擦除

除了程序下载对自身flash读写外，本身也可以通过软件编程对其进行书写，可进行一些数据的存储。
下面就说一下这方面的东西（当然不同的芯片flash有所不同，这里以STM32F429进行介绍，其他芯片即使厂商不同，但是大致的流程和功能是一样的。）

内部FLASH的结构

根据数据手册来看，STM32的内部FLASH有主存储器、系统存储器、OTP区域以及选项字节区域。如图
stm 32 flash,玩转STM32基础篇,stm32,单片机,arm

主存储器：在STM32F4中共有12个主存储器扇区，这12个扇区分为4个16KB、1个64KB以及7个128KB扇区。
系统存储器：器件在系统存储器自举模式下从该存储器启动（就是boot代码，出厂就已经存在的，专门给主存储器下载代码用的，这时候B0外接3.3V,B1接GND的时候从写个存储器启动（像CAN、串口下载就用这个）。
OTP 区域：即一次性可编程区域，共 528 字节，被分成两个部分，前面 512 字节（32 字节为 1 块，分成 16 块），可以用来存储一些用户数据（一次性的，写完一次，永远不可以擦除），后面 16 字节，用于锁定对应块。如图：
选项字节：选项字节用于配置 FLASH 的读写保护、电源管理中的 BOR 级别、软件/硬件看门狗等功能，这部分共 32 字节。可以通过修改 FLASH 的选项控制寄存器修改。

STM32读写

在对FLASH读写之前首先需要对flash解锁。主要流程如下：

1-解锁

因芯片内flash存储的是核心程序，因此默认是上锁的，需要通过软件编写进行解锁（有对应的解锁寄存器和库函数）。

复位后，Flash 控制寄存器 (FLASH_CR) 不允许执行写操作，以防因电气干扰等原因出现对Flash 的意外操作。此寄存器的解锁顺序如下：

1-第一步在 Flash 密钥寄存器 (FLASH_KEYR) 中写入 KEY1 = 0x45670123

2-第二部在 Flash 密钥寄存器 (FLASH_KEYR) 中写入 KEY2 = 0xCDEF89AB

（注意：*如果flash解锁顺序出现错误，将返回总线错误并锁定 FLASH_CR 寄存器，直到下一次复位。也可通过软件将 FLASH_CR 寄存器中的 LOCK 位置为 1 来锁定 FLASH_CR 寄存器。*当 FLASH_SR 寄存器中的 BSY 位为 1 时，将不能在写模式下访问 FLASH_CR 寄存器。BSY 位为 1 时，对该寄存器的任何写操作尝试都会导致 AHB 总线阻塞，直到 BSY 位清零。）

2-数据操作位数

最大操作位数会影响擦除和写入的速度，其中 64 位宽度的操作除了配置寄存器位外，还需要在 Vpp 引脚外加一个 8-9V 的电压源，且其供电时间不得超过一小时，否则 FLASH可能损坏，所以 64 位宽度的操作一般是在量产时对 FLASH 写入应用程序时才使用，大部分应用场合都是用 32 位的宽度。

3-擦除扇区

再下入一块新数据之前，我们需要把之前的数据给擦出掉。步骤如下：

检查 FLASH_SR 寄存器中的 BSY 位，以确认当前未执行任何 Flash 操作
在 FLASH_CR 寄存器中，将 SER 位置 1，并从主存储块的 12 个 (STM32F405xx/07xx和 STM32F415xx/17xx) 或 24 个(STM32F42xxx 和 STM32F43xxx) 扇区中选择要擦的扇区 (SNB)
将 FLASH_CR 寄存器中的 STRT 位置 1
等待 BSY 位清零

批量擦除

如果要进行批量擦除：
检查 FLASH_SR 寄存器中的 BSY 位，以确认当前未执行任何 Flash 操作
将 FLASH_CR 寄存器中的 MER 位置 1(STM32F405xx/07xx 和 STM32F415xx/17xx
器件）
将 FLASH_CR 寄存器中的 MER 和 MER1 位置 1（STM32F42xxx 和 STM32F43xxx
器件）
将 FLASH_CR 寄存器中的 STRT 位置 1
等待 BSY 位清零
注意：如果 FLASH_CR 寄存器中的 MERx 位和 SER 位均置为 1，则无法执行扇区擦除和批量擦除。

编程

标准编程（写入）

当flash擦除完毕后，我们对其进行数据的写入（写入flash就是操作指针、地址这些）。
步骤如下：

Flash 编程顺序如下：

检查 FLASH_SR 中的 BSY 位，以确认当前未执行任何主要 Flash 操作。
将 FLASH_CR 寄存器中的 PG 位置 1。
针对所需存储器地址（主存储器块或 OTP 区域内）执行数据写入操作：
— 并行位数为 x8 时按字节写入
— 并行位数为 x16 时按半字写入
— 并行位数为 x32 时按字写入
— 并行位数为 x64 时按双字写入
等待 BSY 位清零*。* 注意：把 Flash 的单元从“1”写为“0”时，无需执行擦除操作即可进行连续写操作。把 Flash 的
单元从“0”写为“1”时，则需要执行 Flash 擦除操作。
如果同时发出擦除和编程操作请求，首先执行擦除操作。**

编程错误（写入错误）

不允许针对 Flash 执行跨越 128 位行界限的数据编程操作。如果出现这种情况，写操作将不会执行，并且 FLASH_SR 寄存器中的编程对齐错误标志位 (PGAERR) 将置 1。
写访问宽度（字节、半字、字或双字）必须与所选并行位数类型（x8、x16、x32 或 x64）相符。否则，写操作将不会执行，并且 FLASH_SR 寄存器中的编程并行位数错误标志位(PGPERR) 将置 1。
如果未遵循标准的编程顺序（例如，在 PG 位未置 1 时尝试向 Flash 地址写入数据），则操作将中止并且 FLASH_SR 寄存器中的编程顺序错误标志位 (PGSERR) 将置 1。
说白了就两点：一是不能越界，而是按照顺序编写

编程与缓存

如果 Flash 写访问涉及数据缓存中的某些数据，Flash 写访问将修改 Flash 中的数据和缓存中的数据。

如果 Flash 中的擦除操作也涉及数据或指令缓存中的数据，则必须确保在代码执行期间访问这些数据之前将它们重新写入缓存。如果无法可靠执行这一操作，建议将 FLASH_CR 寄存器中的 DCRST 和 ICRST 位置 1，以刷新缓存
注意：I/D 缓存只有在被禁止 (I/DCEN = 0) 的情况下才能刷新

软件编程操作（读写）

我们打开MDK可以看到代码占据了多少flash如下两幅图:
stm 32 flash,玩转STM32基础篇,stm32,单片机,arm

1-Flash解锁的操作（操作库函数，也可以操作寄存器看个人）

文件：
stm32f4xx_flash.c
stm32f4xx_flash.h

我们想要把数据写入flash之前一定要先解锁，否则数据无法写入成功。

#define RDP_KEY                  ((uint16_t)0x00A5)
#define FLASH_KEY1               ((uint32_t)0x45670123)
#define FLASH_KEY2               ((uint32_t)0xCDEF89AB)
#define FLASH_OPT_KEY1           ((uint32_t)0x08192A3B)

#define FLASH_OPT_KEY2           ((uint32_t)0x4C5D6E7F)
//解锁FLASH控件寄存器访问
void FLASH_Unlock(void)
{
  if((FLASH->CR & FLASH_CR_LOCK) != RESET)
  {
    /* Authorize the FLASH Registers access */
    FLASH->KEYR = FLASH_KEY1;
    FLASH->KEYR = FLASH_KEY2;
  }  
}

2-清除标志位

* @brief  Clears the FLASH's pending flags.
  * @param  FLASH_FLAG: specifies the FLASH flags to clear.
  *          This parameter can be any combination of the following values:
  *            @arg FLASH_FLAG_EOP: FLASH End of Operation flag 
  *            @arg FLASH_FLAG_OPERR: FLASH operation Error flag 
  *            @arg FLASH_FLAG_WRPERR: FLASH Write protected error flag 
  *            @arg FLASH_FLAG_PGAERR: FLASH Programming Alignment error flag 
  *            @arg FLASH_FLAG_PGPERR: FLASH Programming Parallelism error flag
  *            @arg FLASH_FLAG_PGSERR: FLASH Programming Sequence error flag
  *            @arg FLASH_FLAG_RDERR: FLASH Read Protection error flag (STM32F42xx/43xxx and STM32F401xx/411xE devices)   
  * @retval None
  */
void FLASH_ClearFlag(uint32_t FLASH_FLAG)
{
  /* Check the parameters */
  assert_param(IS_FLASH_CLEAR_FLAG(FLASH_FLAG));
  
  /* Clear the flags */
  FLASH->SR = FLASH_FLAG;
}

3-擦除

STM32 擦除可以按照块擦除、扇区擦除、擦除全部扇区这三种情况，从上面就能理解这三个的不同

/**
  * @brief  Erases a specified FLASH Sector.
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  *
  * @param  FLASH_Sector: The Sector number to be erased.
  *
  *  @note  For STM32F405xx/407xx and STM32F415xx/417xx devices this parameter can 
  *         be a value between FLASH_Sector_0 and FLASH_Sector_11.
  *
  *         For STM32F42xxx/43xxx devices this parameter can be a value between 
  *         FLASH_Sector_0 and FLASH_Sector_23.
  *
  *         For STM32F401xx devices this parameter can be a value between 
  *         FLASH_Sector_0 and FLASH_Sector_5.
  *
  *         For STM32F411xE devices this parameter can be a value between 
  *         FLASH_Sector_0 and FLASH_Sector_7.
  *
  * @param  VoltageRange: The device voltage range which defines the erase parallelism.  
  *          This parameter can be one of the following values:
  *            @arg VoltageRange_1: when the device voltage range is 1.8V to 2.1V, 
  *                                  the operation will be done by byte (8-bit) 
  *            @arg VoltageRange_2: when the device voltage range is 2.1V to 2.7V,
  *                                  the operation will be done by half word (16-bit)
  *            @arg VoltageRange_3: when the device voltage range is 2.7V to 3.6V,
  *                                  the operation will be done by word (32-bit)
  *            @arg VoltageRange_4: when the device voltage range is 2.7V to 3.6V + External Vpp, 
  *                                  the operation will be done by double word (64-bit)
  *   
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_EraseSector(uint32_t FLASH_Sector, uint8_t VoltageRange)
{
  uint32_t tmp_psize = 0x0;
  FLASH_Status status = FLASH_COMPLETE;

  /* Check the parameters */
  assert_param(IS_FLASH_SECTOR(FLASH_Sector));
  assert_param(IS_VOLTAGERANGE(VoltageRange));
  
  if(VoltageRange == VoltageRange_1)
  {
     tmp_psize = FLASH_PSIZE_BYTE;
  }
  else if(VoltageRange == VoltageRange_2)
  {
    tmp_psize = FLASH_PSIZE_HALF_WORD;
  }
  else if(VoltageRange == VoltageRange_3)
  {
    tmp_psize = FLASH_PSIZE_WORD;
  }
  else
  {
    tmp_psize = FLASH_PSIZE_DOUBLE_WORD;
  }
  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  
  if(status == FLASH_COMPLETE)
  { 
    /* if the previous operation is completed, proceed to erase the sector */
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= tmp_psize;
    FLASH->CR &= SECTOR_MASK;
    FLASH->CR |= FLASH_CR_SER | FLASH_Sector;
    FLASH->CR |= FLASH_CR_STRT;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();
  
    /* if the erase operation is completed, disable the SER Bit */
    FLASH->CR &= (~FLASH_CR_SER);
    FLASH->CR &= SECTOR_MASK; 
  }
  /* Return the Erase Status */
  return status;
}

/**
  * @brief  Erases all FLASH Sectors.
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  *  
  * @param  VoltageRange: The device voltage range which defines the erase parallelism.  
  *          This parameter can be one of the following values:
  *            @arg VoltageRange_1: when the device voltage range is 1.8V to 2.1V, 
  *                                  the operation will be done by byte (8-bit) 
  *            @arg VoltageRange_2: when the device voltage range is 2.1V to 2.7V,
  *                                  the operation will be done by half word (16-bit)
  *            @arg VoltageRange_3: when the device voltage range is 2.7V to 3.6V,
  *                                  the operation will be done by word (32-bit)
  *            @arg VoltageRange_4: when the device voltage range is 2.7V to 3.6V + External Vpp, 
  *                                  the operation will be done by double word (64-bit)
  *   
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_EraseAllSectors(uint8_t VoltageRange)
{
  uint32_t tmp_psize = 0x0;
  FLASH_Status status = FLASH_COMPLETE;
  
  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  assert_param(IS_VOLTAGERANGE(VoltageRange));
  
  if(VoltageRange == VoltageRange_1)
  {
     tmp_psize = FLASH_PSIZE_BYTE;
  }
  else if(VoltageRange == VoltageRange_2)
  {
    tmp_psize = FLASH_PSIZE_HALF_WORD;
  }
  else if(VoltageRange == VoltageRange_3)
  {
    tmp_psize = FLASH_PSIZE_WORD;
  }
  else
  {
    tmp_psize = FLASH_PSIZE_DOUBLE_WORD;
  }  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to erase all sectors */
#if defined(STM32F427_437xx) || defined(STM32F429_439xx)   
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= tmp_psize;
    FLASH->CR |= (FLASH_CR_MER1 | FLASH_CR_MER2);
    FLASH->CR |= FLASH_CR_STRT;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the erase operation is completed, disable the MER Bit */
    FLASH->CR &= ~(FLASH_CR_MER1 | FLASH_CR_MER2);
#endif /* STM32F427_437xx ||  STM32F429_439xx */

#if defined(STM32F40_41xxx) || defined(STM32F401xx) || defined(STM32F411xE) || defined(STM32F446xx)
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= tmp_psize;
    FLASH->CR |= FLASH_CR_MER;
    FLASH->CR |= FLASH_CR_STRT;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the erase operation is completed, disable the MER Bit */
    FLASH->CR &= (~FLASH_CR_MER);
#endif /* STM32F40_41xxx || STM32F401xx || STM32F411xE || STM32F446xx */

  }   
  /* Return the Erase Status */
  return status;
}

/**
  * @brief  Erases all FLASH Sectors in Bank 1.
  *
  * @note   This function can be used only for STM32F42xxx/43xxx devices.
  *  
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one. 
  *  
  * @param  VoltageRange: The device voltage range which defines the erase parallelism.  
  *          This parameter can be one of the following values:
  *            @arg VoltageRange_1: when the device voltage range is 1.8V to 2.1V, 
  *                                  the operation will be done by byte (8-bit) 
  *            @arg VoltageRange_2: when the device voltage range is 2.1V to 2.7V,
  *                                  the operation will be done by half word (16-bit)
  *            @arg VoltageRange_3: when the device voltage range is 2.7V to 3.6V,
  *                                  the operation will be done by word (32-bit)
  *            @arg VoltageRange_4: when the device voltage range is 2.7V to 3.6V + External Vpp, 
  *                                  the operation will be done by double word (64-bit)
  *   
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_EraseAllBank1Sectors(uint8_t VoltageRange)
{
  uint32_t tmp_psize = 0x0;
  FLASH_Status status = FLASH_COMPLETE;
  
  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  assert_param(IS_VOLTAGERANGE(VoltageRange));
  
  if(VoltageRange == VoltageRange_1)
  {
     tmp_psize = FLASH_PSIZE_BYTE;
  }
  else if(VoltageRange == VoltageRange_2)
  {
    tmp_psize = FLASH_PSIZE_HALF_WORD;
  }
  else if(VoltageRange == VoltageRange_3)
  {
    tmp_psize = FLASH_PSIZE_WORD;
  }
  else
  {
    tmp_psize = FLASH_PSIZE_DOUBLE_WORD;
  }  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to erase all sectors */
     FLASH->CR &= CR_PSIZE_MASK;
     FLASH->CR |= tmp_psize;
     FLASH->CR |= FLASH_CR_MER1;
     FLASH->CR |= FLASH_CR_STRT;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the erase operation is completed, disable the MER Bit */
    FLASH->CR &= (~FLASH_CR_MER1);

  }   
  /* Return the Erase Status */
  return status;
}


/**
  * @brief  Erases all FLASH Sectors in Bank 2.
  *
  * @note   This function can be used only for STM32F42xxx/43xxx devices.
  *   
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  *   
  * @param  VoltageRange: The device voltage range which defines the erase parallelism.  
  *          This parameter can be one of the following values:
  *            @arg VoltageRange_1: when the device voltage range is 1.8V to 2.1V, 
  *                                  the operation will be done by byte (8-bit) 
  *            @arg VoltageRange_2: when the device voltage range is 2.1V to 2.7V,
  *                                  the operation will be done by half word (16-bit)
  *            @arg VoltageRange_3: when the device voltage range is 2.7V to 3.6V,
  *                                  the operation will be done by word (32-bit)
  *            @arg VoltageRange_4: when the device voltage range is 2.7V to 3.6V + External Vpp, 
  *                                  the operation will be done by double word (64-bit)
  *   
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_EraseAllBank2Sectors(uint8_t VoltageRange)
{
  uint32_t tmp_psize = 0x0;
  FLASH_Status status = FLASH_COMPLETE;
  
  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  assert_param(IS_VOLTAGERANGE(VoltageRange));
  
  if(VoltageRange == VoltageRange_1)
  {
     tmp_psize = FLASH_PSIZE_BYTE;
  }
  else if(VoltageRange == VoltageRange_2)
  {
    tmp_psize = FLASH_PSIZE_HALF_WORD;
  }
  else if(VoltageRange == VoltageRange_3)
  {
    tmp_psize = FLASH_PSIZE_WORD;
  }
  else
  {
    tmp_psize = FLASH_PSIZE_DOUBLE_WORD;
  }  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to erase all sectors */
     FLASH->CR &= CR_PSIZE_MASK;
     FLASH->CR |= tmp_psize;
     FLASH->CR |= FLASH_CR_MER2;
     FLASH->CR |= FLASH_CR_STRT;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the erase operation is completed, disable the MER Bit */
    FLASH->CR &= (~FLASH_CR_MER2);

  }   
  /* Return the Erase Status */
  return status;
}

4-编程（数据写入）

注意：STM32写入可以按照字、半字、字节单位写入（这点记住每个厂商写入的字节数有的并不相同，像华大的就和这不太一样）

* @brief  在指定地址上编程双字(64位)。
  * @note   This function must be used when the device voltage range is from
  *         2.7V to 3.6V and an External Vpp is present.
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  *  
  * @param  Address: specifies the address to be programmed.
  * @param  Data: specifies the data to be programmed.
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_ProgramDoubleWord(uint32_t Address, uint64_t Data)
{
  FLASH_Status status = FLASH_COMPLETE;

  /* Check the parameters */
  assert_param(IS_FLASH_ADDRESS(Address));

  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to program the new data */
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= FLASH_PSIZE_DOUBLE_WORD;
    FLASH->CR |= FLASH_CR_PG;
  
    *(__IO uint64_t*)Address = Data;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the program operation is completed, disable the PG Bit */
    FLASH->CR &= (~FLASH_CR_PG);
  } 
  /* Return the Program Status */
  return status;
}

/**
  * @brief 在指定地址编程一个字(32位)。
  *
  * @note   This function must be used when the device voltage range is from 2.7V to 3.6V. 
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  *  
  * @param  Address: specifies the address to be programmed.
  *         This parameter can be any address in Program memory zone or in OTP zone.  
  * @param  Data: specifies the data to be programmed.
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_ProgramWord(uint32_t Address, uint32_t Data)
{
  FLASH_Status status = FLASH_COMPLETE;

  /* Check the parameters */
  assert_param(IS_FLASH_ADDRESS(Address));

  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to program the new data */
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= FLASH_PSIZE_WORD;
    FLASH->CR |= FLASH_CR_PG;
  
    *(__IO uint32_t*)Address = Data;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the program operation is completed, disable the PG Bit */
    FLASH->CR &= (~FLASH_CR_PG);
  } 
  /* Return the Program Status */
  return status;
}

/**
  * @brief 在指定地址上编程半字(16位)。
  * @note   This function must be used when the device voltage range is from 2.1V to 3.6V. 
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  * 
  * @param  Address: specifies the address to be programmed.
  *         This parameter can be any address in Program memory zone or in OTP zone.  
  * @param  Data: specifies the data to be programmed.
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_ProgramHalfWord(uint32_t Address, uint16_t Data)
{
  FLASH_Status status = FLASH_COMPLETE;

  /* Check the parameters */
  assert_param(IS_FLASH_ADDRESS(Address));

  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to program the new data */
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= FLASH_PSIZE_HALF_WORD;
    FLASH->CR |= FLASH_CR_PG;
  
    *(__IO uint16_t*)Address = Data;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the program operation is completed, disable the PG Bit */
    FLASH->CR &= (~FLASH_CR_PG);
  } 
  /* Return the Program Status */
  return status;
}

/**
  * @brief  在指定地址编程序一个字节(8位)。
  * @note   This function can be used within all the device supply voltage ranges.  
  *
  * @note   If an erase and a program operations are requested simultaneously,  
  *         the erase operation is performed before the program one.
  * 
  * @param  Address: specifies the address to be programmed.
  *         This parameter can be any address in Program memory zone or in OTP zone.  
  * @param  Data: specifies the data to be programmed.
  * @retval FLASH Status: The returned value can be: FLASH_BUSY, FLASH_ERROR_PROGRAM,
  *                       FLASH_ERROR_WRP, FLASH_ERROR_OPERATION or FLASH_COMPLETE.
  */
FLASH_Status FLASH_ProgramByte(uint32_t Address, uint8_t Data)
{
  FLASH_Status status = FLASH_COMPLETE;

  /* Check the parameters */
  assert_param(IS_FLASH_ADDRESS(Address));

  /* Wait for last operation to be completed */
  status = FLASH_WaitForLastOperation();
  
  if(status == FLASH_COMPLETE)
  {
    /* if the previous operation is completed, proceed to program the new data */
    FLASH->CR &= CR_PSIZE_MASK;
    FLASH->CR |= FLASH_PSIZE_BYTE;
    FLASH->CR |= FLASH_CR_PG;
  
    *(__IO uint8_t*)Address = Data;
  
    /* Wait for last operation to be completed */
    status = FLASH_WaitForLastOperation();

    /* if the program operation is completed, disable the PG Bit */
    FLASH->CR &= (~FLASH_CR_PG);
  } 

  /* Return the Program Status */
  return status;
}

5- 上锁

* @brief  Locks the FLASH control register access
  * @param  None
  * @retval None
  */
void FLASH_Lock(void)
{
  /* Set the LOCK Bit to lock the FLASH Registers access */
  FLASH->CR |= FLASH_CR_LOCK;
}

所以根据以上总结如下步骤（严格来说中间还有一些过程，但是常用的就这几步骤，当然库函数不知这几个，还有获得标志位什么的，这点后面再讲）。

(1) 调用 FLASH_Unlock 解锁；

(2) 调用 FLASH_ClearFlag 清除各种标志位；

(3) 根据起始地址及结束地址计算要擦除的扇区；

(4) 调用 FLASH_EraseSector （或FLASH_EraseAllSectors、FLASH_EraseAllBank1Sectors、FLASH_EraseAllBank2Sectors，一般情况下都是按照扇区删除，有时也会按照块删除）擦除扇区，擦除时按字为单位进行操作；

(5) 调用 FLASH_ProgramWord（或其他都可以）函数向起始地址至结束地址的存储区域都写入数值

(6) 调用 FLASH_Lock 上锁；

(7) 使用指针读取数据内容并校验。

咱们来看一下官网给出的例子

例子

/* 解锁Flash *********************************************************/
  /* 启用flash控制寄存器访问 */
  FLASH_Unlock();
  
  /* 擦除用户Flash区域************************************************/
  /* area defined by FLASH_USER_START_ADDR and FLASH_USER_END_ADDR */

  /* 清除挂起的标志(如果有) */  
  FLASH_ClearFlag(FLASH_FLAG_EOP | FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR | 
                  FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR|FLASH_FLAG_PGSERR); 

  /* 获取开始扇区和结束扇区的数量 */
  uwStartSector = GetSector(FLASH_USER_START_ADDR);
  uwEndSector = GetSector(FLASH_USER_END_ADDR);

  /*开始擦除操作 */
  uwSectorCounter = uwStartSector;
  while (uwSectorCounter <= uwEndSector) 
  {
    /* 设备电压范围假定为[2.7V ~ 3.6V]，操作将通过字完成*/ 
    if (FLASH_EraseSector(uwSectorCounter, VoltageRange_3) != FLASH_COMPLETE)
    { 
      /* 扇区擦除时发生错误。. 
        用户可以在这里添加一些代码来处理这个错误  */
      while (1)
      {
      }
    }
    /* 跳到下一个扇区 */
    if (uwSectorCounter == FLASH_Sector_11)
    {
      uwSectorCounter += 40;
    } 
    else 
    {
      uwSectorCounter += 8;
    }
  }

  /* 按照字写入Flash区 ********************************/
  /* area defined by FLASH_USER_START_ADDR and FLASH_USER_END_ADDR */

  uwAddress = FLASH_USER_START_ADDR;

  while (uwAddress < FLASH_USER_END_ADDR)
  {
    if (FLASH_ProgramWord(uwAddress, DATA_32) == FLASH_COMPLETE)
    {
      uwAddress = uwAddress + 4;
    }
    else
    { 
      /* Error occurred while writing data in Flash memory. 
         User can add here some code to deal with this error */
      while (1)
      {
      }
    }
  }

  /* Lock the Flash to disable the flash control register access (recommended
     to protect the FLASH memory against possible unwanted operation) */
  FLASH_Lock();