Device Family: Arria® V GT, Arria® V GX, Arria® V GZ, Arria® V ST, Arria® V SX, Cyclone® V E, Cyclone® V GT, Cyclone® V GX, Cyclone® V SE, Cyclone® V ST, Cyclone® V SX, Stratix® IV E, Stratix® IV GT, Stratix® IV GX, Stratix® V E, Stratix® V GS, Stratix® V GT, Stratix® V GX

Type: Answers

Area: EMIF, Intellectual Property


IP Product: DDR3 SDRAM Controller MegaCore supporting UniPHY

Why do I see R105 warnings on the DDR3 reset paths when using the Design Assistant tool?

Description

The Design Assistant tool will generate R105 warnings if it detects a reset signal that is generated in one clock domain and used in another clock domain. This warns the user of a potential metastability issue if the signal is not properly synchronized.

All reset input signals to the UniPHY-based DDR3 controller are synchronized to the respective clock domains. You can safely ignore any reset warnings that apply to the logic within the DDR3 controller. The paths are either asynchronous reset signals going to a reset synchronizer, or asynchronous signals that are carefully timed to avoid metastability issues.