ADS131A04: DOUT信号线电平被拉低

背景：ADS131A04作为SPI主设备，STM32L471作为SPI从设备，MCU通过SPI+DMA方式获取数据。

硬件连接：

MCU的SPI和DMA配置：

void InitSPI(void)
{
    /* --- INSERT YOUR CODE HERE --- */
	hspi1.Instance = SPI1;
	hspi1.Init.Mode = SPI_MODE_SLAVE;
	hspi1.Init.Direction = SPI_DIRECTION_2LINES;
	hspi1.Init.DataSize = SPI_DATASIZE_16BIT;
	hspi1.Init.CLKPolarity = SPI_POLARITY_LOW;
	hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;
	hspi1.Init.NSS = SPI_NSS_HARD_INPUT;
	hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
	hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
	hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
	hspi1.Init.CRCPolynomial = 7;
	hspi1.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;
	hspi1.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;
	hspi1.State = HAL_SPI_STATE_RESET;
	if (HAL_SPI_Init(&hspi1) != HAL_OK)
	{
		Error_Handler();
	}
}

void HAL_SPI_MspInit(SPI_HandleTypeDef* spiHandle)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(spiHandle->Instance==SPI1)
  {
  /* USER CODE BEGIN SPI1_MspInit 0 */

  /* USER CODE END SPI1_MspInit 0 */
    /* SPI1 clock enable */
    __HAL_RCC_SPI1_CLK_ENABLE();

    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**SPI1 GPIO Configuration
    PA4     ------> SPI1_NSS
    PA5     ------> SPI1_SCK
    PA6     ------> SPI1_MISO
    PA7     ------> SPI1_MOSI
    */
    GPIO_InitStruct.Pin = ADS131A04_SPI1_NSS_Pin|ADS131A04_SPI1_CLK_Pin|ADS131A04_SPI1_MISO_Pin|ADS131A04_SPI1_MOSI_Pin;
	GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
	GPIO_InitStruct.Pull = GPIO_NOPULL;
	GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
	GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
	HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    /* SPI1 DMA Init */
    /* SPI1_TX Init */
    hdma_spi1_tx.Instance = DMA2_Channel4;
    hdma_spi1_tx.Init.Request = DMA_REQUEST_4;
    hdma_spi1_tx.Init.Direction = DMA_MEMORY_TO_PERIPH;
    hdma_spi1_tx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_spi1_tx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_spi1_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
    hdma_spi1_tx.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
    hdma_spi1_tx.Init.Mode = DMA_NORMAL;
    hdma_spi1_tx.Init.Priority = DMA_PRIORITY_LOW;
    if (HAL_DMA_Init(&hdma_spi1_tx) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(spiHandle,hdmatx,hdma_spi1_tx);

    /* SPI1_RX Init */
    hdma_spi1_rx.Instance = DMA2_Channel3;
    hdma_spi1_rx.Init.Request = DMA_REQUEST_4;
    hdma_spi1_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
    hdma_spi1_rx.Init.PeriphInc = DMA_PINC_DISABLE;
    hdma_spi1_rx.Init.MemInc = DMA_MINC_ENABLE;
    hdma_spi1_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
    hdma_spi1_rx.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
    hdma_spi1_rx.Init.Mode = DMA_NORMAL;
    hdma_spi1_rx.Init.Priority = DMA_PRIORITY_LOW;
    if (HAL_DMA_Init(&hdma_spi1_rx) != HAL_OK)
    {
      Error_Handler();
    }

    __HAL_LINKDMA(spiHandle,hdmarx,hdma_spi1_rx);

    /* SPI1 interrupt Init */
    //HAL_NVIC_SetPriority(SPI1_IRQn, 0, 0);
    //HAL_NVIC_EnableIRQ(SPI1_IRQn);
  /* USER CODE BEGIN SPI1_MspInit 1 */

  /* USER CODE END SPI1_MspInit 1 */
  }
}

问题：ADC上电后，DOUT管脚一开始正常输出0xFF04，但是MCU初始化使能SPI后DOUT信号线电平被拉低，DOUT信号线上拉电阻试过100k，10k以及去掉上拉电阻，依然都是被拉低，可能是什么原因？