I am new to hyperlynx!!
What is the significance of ODT model selection during DDRx batch simulation?
And also ODT behavior?
It will be a great help if you explain in detail.
ODT stands for On-Die Termination. This feature on the DDRx components allows the receiving component to provide termination of the signal when the component is receiving, but disable the termination when not needed. The interaction between the ODT behavior page and the ODT Model Selection page of the DDRx Wizard is described in the User Guide in the section titled DDRx Batch-Mode Wizard - ODT Behavior Page. The documentation is available with the installation of HyperLynx SI/PI or on Support Center (HTTP://support.mentor.com).
2 questions please:
1) I understand ODT is enabled on controller and disabled on DRAM for Read, and ODT is enabled on DRAM, disabled on controller for Write. Why is a selection still required for either controller/DRAM when ODT is disabled?
2) I came across this tutorial: How to Sweep ODTs - HyperLynx DDRx Wizard - Mentor Graphics for running sweeps on ODT. However, I am not seeing the grouping option in the ODT Models window. How can I access this feature to run DDRx Batch Simulation with a ODT sweep, say 40,50,60 Ohms.
1) The case of ODT disabled is generally for when the component is driving. There are options for different drive strength that are chosen with [Model Selector] sections in the IBIS files.
2) Notice in the video that the design is in pre-layout (LineSim). The sweep function in the DDRx Wizard is part of pre-layout. Here is a more recent video that might give you some more information.
If you want to sweep ODT settings and drive strength to optimize configuration in post-layout, then you can run the sweep manager before you run the DDRx Wizard.
I followed your recommendation and it worked, thanks. I saw the sweep option after I exported the selected nets to Line Sim. Here are my results after sweeping across 3 ODT for a single Data Bit as a test: 30 (ODT2), 40 (ODT1) and 60 (ODT3) ohms.
1) However, they all for some reason have 400mV margin for overshoot/undershoot. Does this mean there is no overshoot? Because when I load the waveform there is a little bit of overshoot/undershoot on the graph.
2) I don't see a .sds file in my Receiver Waveform, to look at the eye diagram. Does this require a box to be checked in the simulation wizard?
3) I additionally simulated the differential strobe DQS0 and in my Receiver Waveform folder, for each sweep, I see the following files. What do these mean? Is 'main' DQS0_P and 'opp' DQS0_N?
For sweep 0 ->
1) The margin is the limit - measured. In the HTML report, click on the Margin column header to expand the column into 3. The first of the expanded columns will show the measured value.
2) The SDS file for the eye diagram is written for DDR4 simulation, but not earlier generations. This is based on the requirements in the relevant specifications.
3) For the waveforms of differential signals (CLK or DQS) the _main and _opp files contain the positive and negative, single-ended waveforms. The file without these strings in the name contains the differential signal waveform. This is the important signal. The single-ended signals are useful for debugging if there is a problem in the simulation results.
Thank you very much for your help!
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