Cyclone V with external LPDDR2 show Restore command pending when loading file

Hi all,

We have a board with external LPDDR2 / Cyclone V and the system will show "Restore....." and pending when we loading file.

It looks like there is a problem to write data to external memory.

Due to lack of the real operation of Altera IP, I would like to know where to find the information : how CPU communicate with external memory in the beginning and how CPU check if data write correctly when complete.

Thanks in advance!