Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Renesas Electronics/R7FA6T1AD/SPI0/SPDR#0x0
SPI Data Register
SPDR is the interface with the buffers that hold data for transmission and reception by the RSPI.When accessing in word (SPDCR.SPLW=1), access SPDR.
https://github.com/cmsis-svd/cmsis-svd-data