STM32F767 SPI Bidirectional Receive Mode : More SPI Clocks are output than I expected.

Hello,

I have a question about SPI Bidirectional Mode of STM32F767.

(using HAL Driver / DMA / act as SPI Master)

also, SPI Slave Device is TI LM74 temperature sensor.​

(​https://www.ti.com/product/LM74)

SPI Initialize Parameters are below.

hspi4.Instance = SPI4;
 hspi4.Init.Mode = SPI_MODE_MASTER;
 hspi4.Init.Direction = SPI_DIRECTION_1LINE;
 hspi4.Init.DataSize = SPI_DATASIZE_8BIT;
 hspi4.Init.CLKPolarity = SPI_POLARITY_HIGH;
 hspi4.Init.CLKPhase = SPI_PHASE_2EDGE;
 hspi4.Init.NSS = SPI_NSS_SOFT;
 hspi4.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
 hspi4.Init.FirstBit = SPI_FIRSTBIT_MSB;
 hspi4.Init.TIMode = SPI_TIMODE_DISABLE;
 hspi4.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
 hspi4.Init.CRCPolynomial = 7;
 hspi4.Init.CRCLength = SPI_CRC_LENGTH_DATASIZE;
 hspi4.Init.NSSPMode = SPI_NSS_PULSE_DISABLE;

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To read 2 BYTES from device,

I call function HAL_SPI_Receive_DMA() in my user code,

of course Size parameter is 2.

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When I check the signal waveforms using Oscilloscope,

I expected ​16-bit SPI Clock pulses are output,

but actually there are 24-bit SPI Clock pulses are output.

How can I handle this situation?

Please tell me a solution.

Best Regards,

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