mask register

mihoyo

家人们，我在芯片的reference manual里发现一个不懂的地方，文字描述是这样的：
When a SPI write happens,CRC Engine take data from the SPI write,mask it with the Mask register (registers CRC_REG_MASTER_MASK_xx with xx going from 1 to 3 depending on IP,see Table_6)and store the calculated CRC as the reference CRC within each IP registers.
请问这个mask register应该作何解释啊？