Using 10 g MAC IP example design and simulation example design mode choice for the DEMO. In the simulation frame3, namely padded frame, found that when the length of the field range is greater than 16 'h001a less than 16' h002e, IP core directly through lower tuser signal will be discarded the frame; The length field is less than 16 'h001a, IP nuclear eliminates automatically added zero, please encountered the problem of the engineer or the engineer to help give directions