FAQ

DDR3 IP:  Does the Lattice DDR3 IP core automatically perform the ZQ calibaration and Auto Refresh commands during or after the initialization?

1. During initialization
   The DDR3 controller IP core performs both
   ZQ calibration long (ZQCL) and auto refresh commands during the DDR3
   initialization process. It is a requirement defined by JEDEC DDR3
   specification.
2. After initialization
   After the initialization process is
   completed, the auto-refresh is still performed by the core at the
   interval configured with the tREFI parameter (Refresh interval time) and
   the number for the Auto-Refresh command burst (Auto Refresh Burst
   Count). Therefore, there is no need for you to do anything for the auto
   refresh.

As for the ZQ calibration, it is an optional process for you to perform the calibration on demand basis. The DDR3 IP core does not provide auto-periodic ZQ calibration once the initialization process is completed. However, the core provides two user commands, ZQ_LNG (ZQ calibration long) and ZQ_SHRT (ZQ calibration short), to calibrate the DDR3 memory as needed. Since this process may impact the throughput and it is not a requirement once the initialization is completed, the ZQ calibration control will only run if implemented by the user.