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1. introduction
This document introduces the procedure for simulating PCI Express Gen4: 16 Gbps transmission lines using IBIS-AMI with HyperLynx SI. This presentation will be useful for those who are new to simulation using HyperLynx SI and IBIS-AMI.
In this article, we assume the case where analysis is performed before layout using the LineSim (Pre-Layout Analysis) function of HyperLynx. The device model used will be that of an Agilex™ 7 FPGA F-Tile device.
Reference:
What is HyperLynx SI?
A signal integrity analysis tool for pre- and post-layout verification of SerDes channels, DDRx memory interfaces, and general purpose signal integrity.
What is IBIS-AMI (Algorithmic Modeling Interface)?
Traditional IBIS models lack the ability to model FFE, linear equalization, DFE, CDR, and processing blocks for mixed signals.
IBIS-AMI was developed to enable rapid and accurate statistical analysis and time-domain simulation of high-speed channels. It provides high-speed transmitter and receiver models as executable files, allowing for multi-million bit simulation, crosstalk/jitter analysis, data pattern trending, and modeling of complex blocks such as equalizers and CDRs.
IBIS-AMI consists of the following three model files
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IBIS file (.ibs): analog front end of the buffer model
AMI parameter file (.ami): simulation parameters for equalization and CDR configuration
Algorithm executable files (.dll / .so): The main body of the AMI's operating program that models pre-emphasis, CTLE, DFE, CDR, and ADCE
Waveforms of high-speed serial interfaces:
Specialist column: Waveforms of high-speed serial signals
2. simulation preparation
Preparations for simulation are as follows.
2-1. Simulation Overview
The basic configuration for the simulation of the SERDES circuit is as follows
TX (transmitter) and RX (receiver) IBIS-AMI models and package models are obtained from the device manufacturer.
The PCB is the board element, and S-Parameters, etc., are used according to the system used.
2-2 Preparation of Tools and Model Files
The tools and models used in this contents are as follows
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Simulator
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HyperLynx SI VX.2.13 (Siemens EDA product)
How to download: https://www.macnica.co.jp/en/business/semiconductor/articles/siemens/134907/
How to install: https://www.macnica.co.jp/en/business/semiconductor/articles/siemens/135067/
How to set up a license: https://www.macnica.co.jp/en/business/semiconductor/articles/siemens/136002/
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IBIS-AMI Model and Package Model
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Agilex™ 7 F-Tile General Purpose Transceiver Block IBIS-AMI Model Version 1.7
Available from Altera® (please contact your sales representative)
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2-3. Start HyperLynx
Start HyperLynx SI PI Thermal VX2.13 and open the Schematic Editor by selecting File menu > New Free=Form Schematic > SI.
2-4. Import the prepared IBIS-AMI model into HyperLynx
In order to use the IBIS-AMI model obtained from the manufacturer in HyperLynx, it is necessary to configure the model as follows. If you have already configured the settings, please proceed to the next section.
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Select Models menu > Edit Model Library Paths...
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Open Edit in the Model-library file path(s) field
In the Select Directions for IC-Model Files window, set the folder path containing the model you want to use with Add or Add with Subfolder
2-5. create topology
Use the Schematic Editor to create the channel topology. The following figure shows the corresponding image when configuring a channel. 2-5-1.
2-5-1. Add TX Model
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Select the differential buffer model
2-5-2. add RX model
Add an RX model as well as a TX model.
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Under Select IC Model, select Libraries: agilex_f_gp > Devices: agilex_f_gp > Signal: Rx
The Rx model will be assigned. 2-5-3.
2-5-3. Add TX Package S Parameter Model
Add a TX package model.
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Add an S-Parameter model and double-click it.
Filter by Touchstone in Assign S-Parameter/SPICE Model and select Agilex_Ftile_FGT_DC_70GHz_TX_Typ.s4p
In the Ports column at the bottom of the window > Side pull-down, set Port1/2 to Side: left and Port3/4 to Side: right
The S-Parameter element with the model and port set will be displayed.
2-5-4. Add RX package S-Parameter model
Add RX package model as well as TX.
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Add S-Parameter model, double click, filter by Touchstone in Assign S-Parameter/SPICE Model, and select Agilex_Ftile_FGT_DC_70GHz_RX_Typ.s4p
Set port placement to Port1/2 to right and Port3/4 to left
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You will see the S-Parameter element with the model and ports set
2-5-5. connect each added element
In this article, the analysis will be performed without a PCB model.
2-5-6. Save the Created Schematic
Save the file with any file name (.ffs extension) by selecting File menu > Save As...
3. Simulation
Simulation is performed using the created Schematic. 3-1.
3-1. Analysis Function to be used
The SERDES IBIS-AMI Batch Wizard allows you to simulate multiple SERDES channels in a schematic or board design using the IBIS-AMI model. The simulation allows the user to determine the channel topology, the channel power, the channel frequency, and the channel current.
This simulation allows the user to investigate the channel topology, Rx/Tx parameters, jitter, and crosstalk effects on the channel.
3-2. SERDES IBIS-AMI Batch Wizard Setup
Follow the Wizard to configure settings.
3-2-1 Analysis Options
Select the net to be analyzed and the protocol to be used.
(1) Net to be analyzed : Net002 <-> Net001
(2) Select the protocol to be used: Protocol : PCIE, Type : PCIE4.0-16Gts Electrical Channel.
(3) Specify the name and path of the Wizard configuration file.
3-2-2. Transmitters/Receivers
Set the TX/RX of the net to be analyzed. In this case, U1 is automatically set to TX and U2 to RX because the model is assigned. 3-2-3.
3-2-3 Advanced Eye Diagram
Set the analysis type, stimulus, eye mask, etc.
(1) Analysis type and model: Select Time-domain and Typical.
(2) Stimulus: Select NRZ for Modulation and 128b130b for Sequence.
(3) Eye Mask: Select System PCIE_GEN4_RX
3-2-4. Endpoint 1
Set the AMI parameters for Endpoint 1 (TX). The default settings are used in this case. 3-2-5.
3-2-5. Endpoint 2
Set the AMI parameters for Endpoint 2 (RX), changing Modulation = NRZ. 3-2-6.
3-2-6 Parameter Sweep
Allows you to set the parameter sweep settings used for simulation. The default setting (sweep OFF) is used in this case. (* The sweep function enables simulation of multiple settings at once.)
3-2-7 Channel Sweep
Allows you to set the channel (transmission line) parameter sweep settings. The default setting (sweep OFF) is used in this example.
3-2-8 Report Options
These are optional settings for report output.
(1) Verify the settings only (do not perform simulation): OFF (unchecked) for this time.
(2) PDF report output: OFF (unchecked) for this time
(3) Report output folder: Set an arbitrary path.
3-2-9. Output
Click the Run button to run the simulation. (Depending on the environment used, it may take ~ several minutes to complete.)
When the simulation is complete, an HTML report will be output.
4. Confirming Simulation Results
If you have closed the HTML report displayed when the simulation is complete, you can view the list of generated reports from the View menu > HTML Report Manager, and you can view the target report from the View link on the right of each report.
4-1. Eye Density
Open HTML Report > Advanced Eye > Eye width/height measured at BER 1e-12. Click on the Eye Density Plot column View in the list.
The Eye Density plot will be displayed as shown below. What is being measured by the simulation is the waveform of the RX receive talk.
In this case, the PCIe Gen4 mask is applied, but you can use any mask or the mask of the protocol you use to check.
This completes the simulation.