Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Microchip Technology/ATSAME51J19A/SDHC0/BSR#0x0
BOUNDARY=4K
Block Size
Transfer Block Size
SDMA Buffer Boundary
0 (4K): 4k bytes
1 (8K): 8k bytes
2 (16K): 16k bytes
3 (32K): 32k bytes
4 (64K): 64k bytes
5 (128K): 128k bytes
6 (256K): 256k bytes
7 (512K): 512k bytes
https://github.com/cmsis-svd/cmsis-svd-data