STM32官方flash eeprom代码问题，flash没有擦除就写入

苦工

代码中从状态RECEIVE_DATA换到状态VALID_PAGE时并没有先擦除后使用，RECEIVE_DATA为0xEEEE，VALID_PAGE为0x0000，不擦除怎么能写入呢？望高人指点，是不是我哪里理解错了。问题代码如下
PageStatus1 = (*(__IO uint16_t*)PAGE1_BASE_ADDRESS);
else if (PageStatus1 == RECEIVE_DATA) /* Page0 erased, Page1 receive */
      {
        /* Erase Page0 */
        FlashStatus = FLASH_ErasePage(PAGE0_BASE_ADDRESS);
        /* If erase operation was failed, a Flash error code is returned */
        if (FlashStatus != FLASH_COMPLETE)
        {
          return FlashStatus;
        }
        /* Mark Page1 as valid */
      FlashStatus = FLASH_ProgramHalfWord(PAGE1_BASE_ADDRESS, VALID_PAGE);//直接写入没有先擦除
        /* If program operation was failed, a Flash error code is returned */
        if (FlashStatus != FLASH_COMPLETE)
        {
          return FlashStatus;
        }
      }