about Triple speed ethernet MAC！

Hi,

when I simulated the Triple speed ethernet MAC,I added a data interface contro module to the mac,I found the signal ff_rx_data[7:0] have data stream out,but there are serval "00" bytes in the stream and the signal ff_rx_dsav was deasserted and rx_err[5:0]=6'b000110,how does that happen?

I set the mac interface register as following:

register offsetregister namevalue

x04 scratch0 xAAAAAAAA

0x08 command_config 0x0080_00330

0x0C mac_00 x17231C0 0

0x10 mac_10x 0000CB4A

0x14 frame_length 0x5ee

0x18 pause_quant 0x0f

0x1C RX_section_empty 0x10

0x20 RX_section_full 0x10

0x24 TX_section_empty 0x10

0x28 TX_section_full 0x10

0x2C RX_almost_empty 0x08

0x30 RX_almost_full 0x08

0x34 TX_almost_empty 0x08

0x38 TX_almost_full 0x0A

ox3c 0x00

0x5c 0x0c

0xe8 0x00

0xec 0x00