ST STM32L4+ Series Reference Manual page 1892

Serial peripheral interface (SPI)
Bits 15:0 TXCRC[15:0]: Tx CRC register
1892/2301
When CRC calculation is enabled, the TXCRC[7:0] bits contain the computed CRC value of
the subsequently transmitted bytes. This register is reset when the CRCEN bit of SPIx_CR1
is written to 1. The CRC is calculated serially using the polynomial programmed in the
SPIx_CRCPR register.
Only the 8 LSB bits are considered when the CRC frame format is set to be 8-bit length
(CRCL bit in the SPIx_CR1 is cleared). CRC calculation is done based on any CRC8
standard.
The entire 16-bits of this register are considered when a 16-bit CRC frame format is selected
(CRCL bit in the SPIx_CR1 register is set). CRC calculation is done based on any CRC16
standard.
A read to this register when the BSY flag is set could return an incorrect value.
RM0432 Rev 6
RM0432