External Memory Interface Handbook Volume 3: Reference Material

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

1.7.1.9. NIOS II-based Sequencer Calibration and Diagnostics

Calibration must initialize all memory devices before they can operate properly. The sequencer performs this memory initialization stage when it takes control of the PHY at startup.

Calibrating the read datapath comprises the following steps:

  • Calibrate DQS enable cycle and phase.
  • Perform read per-bit deskew to center the strobe signal within data valid window.
  • Reduce LFIFO latency.

Calibrating the write datapath involves the following steps:

  • Center align DQS with respect to DQ.
  • Align DQS with mem_clk.

The sequencer estimates the read and write margins under noisy conditions, by sweeping input and output DQ and DQS delays to determine the size of the data valid windows on the input and output sides. The sequencer stores this diagnostic information in the local memory and you can access it through the debugging interface.

When the diagnostic test finishes, control of the PHY interface passes back to the controller and the sequencer issues a pass or fail signal.

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