Undesirable triggering emif_reset

Hi, i am new in SoC development and i started with Stratix10 SoC DevKit. When i tried to load an example project from the golden system reference manual, i received an error messages on my PC ( i communicate with the board through the serial port ).
“DDR: triggering emif_reset
DDR: emif_reset triggered succesly”
so three times and then
“DDR: Error as SDRAM calibration failed
DDR: Initialization failed”
i guess, i have not released SDRAM-Block from reset or something similar. The Problem is that i cant find the emif_reset interface in the example design. So neither in Quartus’s Platform Designer nor in ref manuals.
How can i solve this problem?