DDR3 UniPHY IP Initiailize problem

Hello, I' trying to use the DDR3 UniPHY IP.

I generate the clock and reset signal and input to the IP.

After setting the global_reset_n high, the IP set the afi_reset_n low after 15 afi_clock.

And set the mem_reset_n low after more 2 afi_clock.

But the IP won't set the mem_reset_n high to start initialization.

(The IP example will set mem_reset_n high almost at 16 us)

Can someone give me some suggestions?

Thank you.