custom IP of the DM9000, can't read from the registers of the DM9000 IC.

Dear everyone,

I have made a custom IP core of the DM9000, but I can't use nios II to read the registers of DM9000, I use the IORD, it can't return the right value, when I check it through signal tap II, I found that the read_n ( this signal is set in the componant editor with the read_n siganl type) was always low, when I used the IORD to send a read apply, the read_n is a high pulse, but I think that the read_n should be low active, it is high when there is no read apply. who encountered the same question, who can help me, thank you!