External Memory Interface Handbook Volume 3: Reference Material

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

1.17.1. Calibration Overview

Calibration configures the memory interface (PHY and I/Os) so that data can pass reliably to and from memory.

The sequencer illustrated in the figure below calibrates the PHY and the I/Os. To correctly transmit data between a memory device and the FPGA at high speed, the data must be center-aligned with the data clock.

Calibration also determines the delay settings needed to center-align the various data signals with respect to their clocks. I/O delay chains implement the required delays in accordance with the computed alignments. The Nios II-based sequencer performs two major tasks: FIFO buffer calibration and I/O calibration. FIFO buffer calibration adjusts FIFO lengths and I/O calibration adjusts any delay chain and phase settings to center-align data signals with respect to clock signals for both reads and writes. When the calibration process completes, the sequencer shuts off and passes control to the memory controller.

Figure 23. Sequencer in Memory Interface Logic


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