External Memory Interface Handbook Volume 2: Design Guidelines

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ID 683385
Date 5/08/2017
Public
Document Table of Contents

2.6.2. Understanding Channel Signal Integrity Measurement

To measure channel signal integrity you need to measure the channel loss for various signals. For a particular signal or signal trace, channel loss is defined as loss of the eye width at +/- VIH(ac and dc) +/- VIL(ac and dc). VIH/VIL above or below VREF is used to align with various requirements of the timing model for memory interfaces.

The example below shows a reference eye diagram where the channel loss on the setup- or leading-side of the eye is equal to the channel loss on the hold- or lagging-side of the eye; howevever, it does not necessarily have to be that way. Because Intel's calibrating PHY will calibrate to the center of the read and write eye, the Board Settings tab has parameters for the total extra channel loss for Write DQ and Read DQ. For address and command signals which are not-calibrated, the Board Settings tab allows you to enter setup- and hold-side channel losses that are not equal, allowing the Quartus Prime software to place the clock statically within the center of the address and command eye.

Figure 21. Equal Setup and Hold-side Losses

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