ADC配置检测3个通道，DMA传输长度为1，OVR标志不会置1，为什么？

不知道自己哪里理解错误了，求指教

if (HAL_ADC_Start_DMA(&hadc1,(uint32_t *)aADCxConvertedData,1) != HAL_OK)
{

Error_Handler();
}


///////初始配置


hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;//ADC_CLOCK_ASYNC_DIV1;//
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;//多通道扫描要使能,单通道扫描关闭
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc1.Init.LowPowerAutoWait = DISABLE;//等待转换模式
hadc1.Init.LowPowerAutoPowerOff = DISABLE;//自动关闭模式
hadc1.Init.ContinuousConvMode = DISABLE;//单次或连续转换模式
hadc1.Init.NbrOfConversion = 3;//转换通道3个
hadc1.Init.DiscontinuousConvMode = DISABLE;//不连续模式

hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

hadc1.Init.DMAContinuousRequests = DISABLE;//ENABLE;
hadc1.Init.Overrun = ADC_OVR_DATA_OVERWRITTEN;//溢出覆盖数据
hadc1.Init.SamplingTimeCommon1 = ADC_SAMPLETIME_1CYCLE_5;
hadc1.Init.SamplingTimeCommon2 = ADC_SAMPLETIME_160CYCLES_5;
hadc1.Init.OversamplingMode = DISABLE;//过采样器使能
//        hadc1.Init.OversamplingMode      = ENABLE;
hadc1.Init.Oversampling.Ratio         = ADC_OVERSAMPLING_RATIO_16;
hadc1.Init.Oversampling.RightBitShift = ADC_RIGHTBITSHIFT_4;
hadc1.Init.Oversampling.TriggeredMode = ADC_TRIGGEREDMODE_SINGLE_TRIGGER;
hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;
if (HAL_ADC_Init(&hadc1) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_4;
sConfig.Rank = ADC_REGULAR_RANK_1;
sConfig.SamplingTime = ADC_SAMPLINGTIME_COMMON_2;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;
sConfig.Rank = ADC_REGULAR_RANK_2;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_VREFINT;
sConfig.Rank = ADC_REGULAR_RANK_3;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}


/* ADC1 DMA Init */

/* ADC1 Init */
hdma_adc1.Instance = DMA1_Channel1;
hdma_adc1.Init.Request = DMA_REQUEST_ADC1;
hdma_adc1.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_adc1.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_adc1.Init.MemInc = DMA_MINC_ENABLE;
hdma_adc1.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
hdma_adc1.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
hdma_adc1.Init.Mode = DMA_NORMAL;//DMA_CIRCULAR;//
hdma_adc1.Init.Priority = DMA_PRIORITY_HIGH;
if (HAL_DMA_Init(&hdma_adc1) != HAL_OK)
{
Error_Handler();
}

__HAL_LINKDMA(hadc,DMA_Handle,hdma_adc1);