External Memory Interface Handbook Volume 3: Reference Material

ID 683841
Date 7/24/2019
Public
Document Table of Contents

3.17.4. Ping Pong PHY Calibration

A Ping Pong PHY interface is calibrated as a regular interface of double width.

Calibration of a Ping Pong PHY interface incorporates two sequencers, one on the primary hard memory controller I/O bank, and one on the secondary hard memory controller I/O bank. To ensure that the two sequencers issue instructions on the same memory clock cycle, the Nios II processor configures the sequencer on the primary hard memory controller to receive a token from the secondary interface, ignoring any commands from the Avalon bus. Additional delays are programmed on the secondary interface to allow for the passing of the token from the sequencer on the secondary hard memory controller tile to the sequencer on the primary hard memory controller tile. During calibration, the Nios II processor assumes that commands are always issued from the sequencer on the primary hard memory controller I/O bank. After calibration, the Nios II processor adjusts the delays for use with the primary and secondary hard memory controllers.

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