uint32_tmask_byte_control4:6;/*These bits are mask control bits for comparison of each of the EMACADDR4 bytes. When set high the MAC does not compare the corresponding byte of received DA or SA with the contents of EMACADDR4 registers. Each bit controls the masking of the bytes as follows: Bit[29]: EMACADDR4 High [15:8]. Bit[28]: EMACADDR4 High [7:0]. Bit[27]: EMACADDR4 Low [31:24]. Bit[24]: EMACADDR4 Low [7:0].You can filter a group of addresses (known as group address filtering) by masking one or more bytes of the address.*/