stm32 F0系列AD转换，初始化AD后，无需配置相应的io为模拟输入，为什么？

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stm32 F0系列AD转换，初始化AD后，无需配置相应的io为模拟输入，为什么？
代码如下：
/**
  ******************************************************************************
  * @file    ADC_DMA/main.c
  * @author  MCD Application Team
  * @version V1.0.0
  * @date    23-March-2012
  * @brief   Main program body
  ******************************************************************************
  * @attention
  *
  * <h2><center>&copy; COPYRIGHT 2012 STMicroelectronics</center></h2>
  *
  * 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.
  *
  ******************************************************************************
  */
/* Includes ------------------------------------------------------------------*/
#include "stm32f0xx.h"
#include "stm32f0_discovery.h"
/** @addtogroup STM32F0_Discovery_Peripheral_Examples
  * @{
  */
/** @addtogroup ADC_DMA
  * @{
  */
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
#define ADC1_DR_Address                0x40012440
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
__IO uint32_t TempSensVoltmv = 0, VrefIntVoltmv = 0;
__IO uint16_t RegularConvData_Tab[2];
/* Private function prototypes -----------------------------------------------*/
void ADC1_CH_DMA_Config(void);
/* Private functions ---------------------------------------------------------*/
/**
  * @brief  Main program.
  * @param  None
  * @retval None
  */
int main(void)
{
  /*!< At this stage the microcontroller clock setting is already configured,
       this is done through SystemInit() function which is called from startup
       file (startup_stm32f0xx.s) before to branch to application main.
       To reconfigure the default setting of SystemInit() function, refer to
       system_stm32f0xx.c file
     */
  
  /* ADC1 channel with DMA configuration */
  ADC1_CH_DMA_Config();
  /* Infinite loop */
  while (1)
  {
    /* Test DMA1 TC flag */
    while((DMA_GetFlagStatus(DMA1_FLAG_TC1)) == RESET );
   
    /* Clear DMA TC flag */
    DMA_ClearFlag(DMA1_FLAG_TC1);
   
    /* Convert temperature sensor voltage value in mv */
    TempSensVoltmv = (uint32_t)((RegularConvData_Tab[0]* 3300) / 0xFFF);
   
    /* Convert Vref voltage value in mv */
    VrefIntVoltmv  = (uint32_t)((RegularConvData_Tab[1]* 3300) / 0xFFF);  
  
  }
}
/**
  * @brief  ADC1 channel with DMA configuration
  * @param  None
  * @retval None
  */
void ADC1_CH_DMA_Config(void)
{
  ADC_InitTypeDef     ADC_InitStructure;
  DMA_InitTypeDef     DMA_InitStructure;
  
  /* ADC1 DeInit */  
  ADC_DeInit(ADC1);
  
  /* ADC1 Periph clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
  
  /* DMA1 clock enable */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1 , ENABLE);
  
  /* DMA1 Channel1 Config */
  DMA_DeInit(DMA1_Channel1);
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC1_DR_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)RegularConvData_Tab;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  DMA_InitStructure.DMA_BufferSize = 2;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);
  
  /* DMA1 Channel1 enable */
  DMA_Cmd(DMA1_Channel1, ENABLE);
  
  /* ADC DMA request in circular mode */
  ADC_DMARequestModeConfig(ADC1, ADC_DMAMode_Circular);
  
  /* Enable ADC_DMA */
  ADC_DMACmd(ADC1, ENABLE);  
  
  /* Initialize ADC structure */
  ADC_StructInit(&ADC_InitStructure);
  
  /* Configure the ADC1 in continous mode withe a resolutuion equal to 12 bits  */
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_ScanDirection = ADC_ScanDirection_Backward;
  ADC_Init(ADC1, &ADC_InitStructure);

  /* Convert the ADC1 temperature sensor  with 55.5 Cycles as sampling time */
  ADC_ChannelConfig(ADC1, ADC_Channel_TempSensor , ADC_SampleTime_55_5Cycles);  
  ADC_TempSensorCmd(ENABLE);
  
  /* Convert the ADC1 Vref  with 55.5 Cycles as sampling time */
  ADC_ChannelConfig(ADC1, ADC_Channel_Vrefint , ADC_SampleTime_55_5Cycles);
  ADC_VrefintCmd(ENABLE);
  
  /* ADC Calibration */
  ADC_GetCalibrationFactor(ADC1);
  
  /* Enable ADC1 */
  ADC_Cmd(ADC1, ENABLE);     
  
  /* Wait the ADCEN falg */
  while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_ADEN));
  
  /* ADC1 regular Software Start Conv */
  ADC_StartOfConversion(ADC1);
}
#ifdef  USE_FULL_ASSERT
/**
  * @brief  Reports the name of the source file and the source line number
  *         where the assert_param error has occurred.
  * @param  file: pointer to the source file name
  * @param  line: assert_param error line source number
  * @retval None
  */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
  /* Infinite loop */
  while (1)
  {
  }
}
#endif
/**
  * @}
  */
/**
  * @}
  */
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

wo8484388

应该是内部温度传感器