Specifying Thresholds for DDR5 Real-Time Eye

To perform clock recovery and real-time eye on DDR5 DQ (Data) signals, you must first properly specify thresholds for the DDR5 waveforms.

The DDR5 signals will have different threshold settings, so clear the Track Global Threshold option for the DDR5 waveforms the thresholds apply to.

• The DQ (Data) signal is typically a rectangular waveform signal where read and write bursts will have different amplitudes due to the different circuitry and paths driving the signal.

  In this case, the ± Hysteresis threshold definition works well because it is easy to find a midpoint and small hysteresis value that works for both amplitudes.

• The DQS (Strobe) signal has different amplitudes due to the different circuitry and paths driving the signal (like the DQ signal), but it also has a high-impedance (idle) middle level.

  In this case, the Custom Percent (%) threshold definition works well because the lower and upper threshold levels need to be beyond the high-impedance level's reflections and noise while still being within both read strobe and write strobe amplitudes.

• The CA4 (Command/Address 4) signal is typically a rectangular waveform with regular amplitudes.

  In this case, the ± Hysteresis threshold definition works well because of the regular amplitude and consistent mid-level.

See General Thresholds.