stm32模擬eeprom要實現flash數據頁轉存，實現函數為

 1 /**
 2 * @brief Transfers last updated variables data from the full Page to
 3 * an empty one.
 4 * @param VirtAddress: 16 bit virtual address of the variable
 5 * @param Data: 16 bit data to be written as variable value
 6 * @retval Success or error status:
 7 * - FLASH_COMPLETE: on success
 
 8 * - PAGE_FULL: if valid page is full
 9 * - NO_VALID_PAGE: if no valid page was found
10 * - Flash error code: on write Flash error
11 */
12 uint16_t EE_PageTransfer(uint16_t VirtAddress, uint16_t Data)

這個函數的過程為：

1. 得到當前可讀有效頁，並設置其為oldPage，另一頁為NewPage。

2. 給NewPage設置RECEIVE_DATA狀態

3.初始化寫地址 切換到接收頁

4. 寫一個當前要保存的數據，如果單純發起一次轉存，則隨意保存一個數據。

5. 讀出除第三步保存過的所有要保存的變量數據，保存到NewPage中。

6. 擦除OldPage（執行時間15ms-2s，根據扇區大小而定（1K~128K））

7. 給NewPage設置VALID_PAGE狀態。

第5步中 Get the valid Page end Address

1 if((PageStatus0 == RECEIVE_DATA)||(PageStatus1 == RECEIVE_DATA))//當頁傳輸的時候把valid Page end Address切換到可讀有效頁的最後
2 {
3      Address = (uint32_t)((EEPROM_START_ADDRESS - 2
 
) + (uint32_t)((1 + ValidPage) * PAGE_SIZE));
4  }
5  else
6  {
7      Address=CurWrAddress-2;
8  }

轉存完成後的各頁的狀態：NewPage:VALID_PAGE;

　　　　　　　　　　　 OldPage:ERASED;

但是在轉存過程中系統斷電，則各頁的狀態可能出現

1.NewPage:ERASED; OldPage:VALID_PAGE; 這種情況發生在EE_PageTransfer函數執行到第二步之前系統掉電。那麽這次轉存過程就當沒有發生過，要保存的那個數據變量也得不到保存。

2.NewPage:RECEIVE_DATA; OldPage:VALID_PAGE; 這種情況發生在EE_PageTransfer函數執行到第六步之前系統掉電。

3.NewPage:RECEIVE_DATA; OldPage:ERASED; 這種情況發生第六步執行過程中系統掉電。

主要討論第2、3中情況下開機初始化eeprom的時候處

 1 //NewPage:RECEIVE_DATA; OldPage:VALID_PAGE; 2 InitCurrWrAddress();//初始化寫地址
 2 //這裏NewPage為PAGE1 OldPage為Page0
 3                   
 4   /* Transfer data from Page0 to Page1 */
 5   for (VarIdx = 0; VarIdx < NumbOfVar; VarIdx++)
 6   {
 7      if ((*(__IO uint16_t*)(PAGE1_BASE_ADDRESS + 6)) == VirtAddVarTab[VarIdx])
 8      {
 9           x = VarIdx;
10      }
11      if (VarIdx != x)
12      {
13          /* Read the last variables‘ updates */
14           ReadStatus = EE_ReadVariable(VirtAddVarTab[VarIdx], &DataVar);
15            /* In case variable corresponding to the virtual address was found */
16           if (ReadStatus != 0x1)
17           {
18          　　/* Transfer the variable to the Page1 */
19          　　 EepromStatus =     EE_VerifyPageFullWriteVariable(VirtAddVarTab[VarIdx], DataVar);
20             /* If program operation was failed, a Flash error code is returned */
21            if (EepromStatus != FLASH_COMPLETE)
22            {
23        　　　　　return EepromStatus;
24            }
25          }
26      }
27  }//for (VarIdx...
28  /* Mark Page1 as valid */
29  FlashStatus = FLASH_ProgramHalfWord(PAGE1_BASE_ADDRESS, VALID_PAGE);
30  /* If program operation was failed, a Flash error code is returned */
31  if (FlashStatus != FLASH_COMPLETE)
32  {
33      return FlashStatus;
34  }
35 /* Erase Page0 */
36 FlashStatus = FLASH_EraseSector(PAGE0_ID, VOLTAGE_RANGE);
37 /* If erase operation was failed, a Flash error code is returned */
38 if (FlashStatus != FLASH_COMPLETE)
39 {
40    return FlashStatus;
41 }

過程：

1.讀出除第一個位置保存過的所有要保存的變量數據，保存到NewPage中。

2. 把RECEIVE_DATA狀態改為VALID_PAGE

3. 擦除OldPage。

 1   //NewPage:RECEIVE_DATA; OldPage:ERASED;OldPage:Page0 NewPage:Page1
 2   /* Erase Page0 */
 3   FlashStatus = FLASH_EraseSector(PAGE0_ID, VOLTAGE_RANGE);
 4   /* If erase operation was failed, a Flash error code is returned */
 5   if (FlashStatus != FLASH_COMPLETE)
 6   {
 7      return FlashStatus;
 8   }
 9   /* Mark Page1 as valid */
10  FlashStatus = FLASH_ProgramHalfWord(PAGE1_BASE_ADDRESS,VALID_PAGE);
11  /* If program operation was failed, a Flash error code is returned */
12  if (FlashStatus != FLASH_COMPLETE)
13  {
14     return FlashStatus;
15  }

第三種情況下

1. 擦除OldPage

2. 把RECEIVE_DATA狀態改為VALID_PAGE

STM32的flash數據頁轉存過程分析！