This page provides detailed information regarding DDR configuration and setting up IBIS simulations for the UltraScale and UltraScale+ family of FPGAs and MPSoCs.

Table of Contents

Introduction

Xilinx has determined through extensive simulation and characterization, the FPGA and DRAM configuration settings including Drive Strength, ODT, and Vref.  These values are used when the IP is generated.  This information is captured in the sections below.  The Custom IBIS models capture this information and can be used for board-level simulation.

This guide provides the following details and guidance

• Supported PL and PS DRAMs

• ODT and V_REF configuration settings for each supported DRAM interface

• IBIS Models for use in simulations

• Available resources for HyperLynx and ADS simulation tools

• HyperLynx DDRx tips

FPGA and MPSoC Supported DRAM

The UltraScale and UltraScale+ families of FPGAs and MPSoCs support several different DRAM technologies and configurations.  This chapter provides an overview of the supported DRAMs and configurations.       

Supported DRAM technologies

• FPGA, Programmable Logic (PL), DRAM IP

  • DDR4

  • DDR3/3L

• MPSoC, Processing System (PS), Configured with Processor Configuration Wizard (PCW)

  • DDR4

  • LPDDR4

  • DDR3/3L

  • LPDDR3

• MPSoC devices support both PL and PS DRAM interfaces

Supported DRAM configurations

• Table 1 outlines the supported PL DRAM configurations, PL DRAM performance, and configurations found in DS923, Maximum Physical Interface (PHY) Rate for Memory Interfaces Table.

• Table 2 outlines the supported PS DRAM performance and configurations, PS DRAM configurations found in DS925, Configuration and Security Unit Performance Table.

Table 1: Supported PL DRAM Configurations

 Table 2: Supported PS DRAM Configurations

PL DRAM IP Drive Strength, ODT, and V_REF Configuration

The PL DRAM IP has been characterized and tested to identify the optimal drive strength, ODT, and V_REF settings.  This chapter provides the values that will always be used for the PL DRAM IP UltraScale and UltraScale+ DDR3/3L and DDR4 DRAM interfaces.  The Memory Controller supports the following calibration routines.  For more details on these routines, please see PG150.

• Write Leveling

  • Write DQS to DQ Deskew

• Read Leveling

  • Per-Bit Deskew

  • Read DQS Centering

• Write Latency Calibration

  • Write DQS to CK alignment

UltraScale PL DDR4

• Table 3 provides PL DDR4 FPGA drive strength and ODT configurations

  • FPGA Slew Rate is always FAST

• Table 4 provides PL DDR4 DRAM drive strength and ODT configurations

• Table 5 provides PL DDR4 V_REF configurations

Table 3: PL DDR4 FPGA drive strength & ODT configurations

 Table 4: PL DDR4 DRAM drive strength and ODT configurations

 Table 5: PL DDR4 V_REF configurations

UltraScale PL DDR3/3L

• Table 6 provides PL DDR3/3L FPGA drive strength & ODT configuration

  • FPGA Slew Rate is always FAST

• Table 7 provides PL DDR3/3L DRAM drive strength and ODT configuration

Table 6: PL DDR3/3L FPGA drive strength & ODT configuration

 Table 7: PL DDR3/3L DRAM drive strength and ODT configuration

UltraScale+ PL DDR4

• Table 8 provides PL DDR4 FPGA drive strength & ODT configurations

  • FPGA Slew Rate is always FAST

• Table 9 provides PL DDR4 DRAM drive strength and ODT configurations

• Table 10 provides PL DDR4 V_REF configurations

Table 8: PL DDR4 FPGA drive strength & ODT configurations

Table 9: PL DDR4 DRAM drive strength and ODT configurations

Table 10: PL DDR4 V_REF configurations

UltraScale+ PL DDR3/3L

• Table 11 provides PL DDR3/3L FPGA drive strength & ODT configurations

  • FPGA Slew Rate is always FAST

• Table 12 provides PL DDR3/3L DRAM drive strength and ODT configurations

Table 11: PL DDR3/3L FPGA drive strength & ODT configurations

Table 12: PL DDR3/3L DRAM drive strength and ODT configurations

Manually finding the DRAM Configuration Settings

The settings from the previous configuration tables can be manually found in the following locations

• DRAM Configuration, drive strength, ODT, and V_REF (read & write)

  • ddrX_0 IP --> Synthesis --> ddrX_0_ddrX.sv

    • Search for the configuration settings of the DRAM type being used

• FPGA IO Standard, drive strength and ODT value

  • XDC: write_xdc

  • IBIS: write_ibis

  • FPGA Slew Rate is always FAST

Configuration Settings

DDR4

• Output Driver Impedance: MR1 [2:1]

• R_TT(nom): MR1 [10:8]

• Dynamic ODT R_TT(wr): MR2 [11:9]

• R_TT(park): MR5 [8:6]

• V_REF Write: MR6 [6:0] (V_REFDQ Training Values: JESD79-4B, Table 16 or JESD79-4C, Table 34)

• Vref Read: RD_V_REF_VAL (UG571, v1.12, Table 1-11)

DDR3/3L

• DRAM Settings

  • Output Drive Strength, MR1[5,1]

  • R_TT(nom), MR1 [9,6,2]

  • R_TT(wr), MR2[10:9]

FPGA Configuration Settings

Finding IO details in the xdc

• Perform write_xdc from an elaborated design

  • Review the following properties

    • IOSTANDARD

    • OUTPUT_IMPEDANCE

    • SLEW

    • ODT

Example configuration: PL DDR4, 1dpc (1 DIMM per Channel), dual-rank,

• DQ Signals (DQ0)

  • IOSTANDARD

    • set_property IOSTANDARD POD12_DCI [get_ports {c0_ddr4_dq[0]}]

  • OUTPUT_IMPEDANCE

    • set_property OUTPUT_IMPEDANCE RDRV_40_40 [get_ports {c0_ddr4_dq[0]}]

  • SLEW

    • set_property SLEW FAST [get_ports {c0_ddr4_dq[0]}]

  • ODT: R_TT_60

    • set_property ODT R_TT_60 [get_ports {c0_ddr4_dq[0]}]

  • Equalization

    • set_property EQUALIZATION EQ_LEVEL3 [get_ports [list {c0_ddr4_dq[0]}

  • Pre-Emphasis

    • set_property PRE_EMPHASIS RDRV_240 [get_ports [list {c0_ddr4_dq[0]}

• ADDR Signals (ADDR0)

  • IOSTANDARD

    • set_property IOSTANDARD SSTL12_DCI [get_ports {c0_ddr4_adr[0]}]

  • OUTPUT_IMPEDANCE

    • set_property OUTPUT_IMPEDANCE RDRV_40_40 [get_ports {c0_ddr4_adr[0]}]

  • SLEW

    • set_property SLEW FAST [get_ports {c0_ddr4_adr[0]}]

  • ODT

    • N/A, Address is output only

Finding details in custom IBIS Model

Perform write_ibis from an elaborated design (See Vivado Generated, Custom IBIS Models section)

Locate the desired signal under the [Pin] keyword, the IBIS model name is called out to the right of the signal name.  This IBIS model name contains all the active settings.

Example configuration: PL DDR4, 1dpc, dual rank

• DQ Signals (DQ0)

  • c0_ddr4_dq[0]   HP_POD12_DCI_F_OUT40_IN60_PE2400

    • IOSTANDARD = POD12 (POD12_DCI)

    • OUTPUT_IMPEDANCE = 40 (OUT40)

    • SLEW = FAST (F)

    • ODT = 60 (IN60)

• Address Signals (ADDR0)

  • c0_ddr4_adr[0]  HP_SSTL12_DCI_F_OUT40

    • IOSTANDARD = SSTL12 (SSTL12_DCI)

    • OUTPUT_IMPEDANCE = 40 (OUT40)

    • SLEW = FAST (F) 

Zynq UltraScale+ MPSoC DDR Subsystem Drive Strength, ODT and V_REF Configuration

The Zynq MPSoC PS DDR subsystem Memory Controller has been characterized and tested to identify the optimal drive strength, ODT and V_REF (initial value) settings.  This chapter provides the values that will always be used for the Zynq MPSoC PS Memory Controller with DDR3/3L, LPDDR3, DDR4 and LPDDR4 DRAM interfaces.  PS DDR drivers do not have discrete settings for drive strength or slew rate.  The drive strength and slew rate can’t be adjusted or read. The drive strength and slew rate settings have been derived from characterization.   The Memory Controller supports the following calibration routines. 

• Write Leveling

  • Write DQS to DQ Deskew

• Read Leveling

  • Per-Bit Deskew

  • Read DQS Centering

• Write Latency Calibration

  • Write DQS to CK alignment

• V_REF training

  • The DRAM Write V_REF is calibrated, initial values are listed, the initial values represent the typical value.

Zynq MPSoC PS DDR4

• Table 13 provides PS DDR4 FPGA drive strength & ODT configurations

  • FPGA Slew Rate can’t be adjusted and is always FAST

• Table 14 provides PS DDR4 DRAM drive strength and ODT configurations

• Table 15 provides PS DDR4 V_REF (initial value) configurations

Table 13: PS DDR4 FPGA drive strength & ODT configurations

Table 14: PS DDR4 DRAM drive strength and ODT configurations

Table 15: PS DDR4 V_REF (initial value) configurations

Zynq MPSoC PS LPDDR4

• Table 16 provides PS LPDDR4 FPGA drive strength & ODT configurations

  • FPGA Slew Rate can’t be adjusted and is always FAST

• Table 17 provides PS LPDDR4 DRAM drive strength and ODT configurations

• Table 18 provides PS LPDDR4 V_REF (initial value) configurations

Table 16: PS LPDDR4 FPGA drive strength & ODT configurations

Table 17: PS LPDDR4 DRAM drive strength and ODT configurations

Table 18: PS LPDDR4 V_REF (initial value) configurations

Zynq MPSoC PS DDR3/3L

• Table 19 provides PS DDR3/3L FPGA drive strength & ODT configurations

  • FPGA Slew Rate can’t be adjusted and is always FAST

• Table 20 provides PS DDR3/3L DRAM drive strength and ODT configurations

Table 19: PS DDR3/3L FPGA drive strength & ODT configurations

Table 20: PS DDR3/3L DRAM drive strength and ODT configurations

UltraScale+ PS LPDDR3

• Table 21 provides PS LPDDR3 FPGA drive strength & ODT configurations

  • FPGA Slew Rate can’t be adjusted and is always FAST

• Table 22 provides PS LPDDR3 DRAM drive strength and ODT configurations

Table 21: PS LPDDR3 FPGA drive strength & ODT configurations

Table 22: PS LPDDR3 DRAM drive strength and ODT configurations

Manually finding the DRAM Configuration Settings

The settings from the previous configuration tables can be manually found in the following locations

• DRAM Configuration, drive strength, ODT and V_REF (if applicable)

  • Export Hardware --> design.hdf --> psu_int.c

• FPGA IO Standard, drive strength and ODT value

  • IBIS: write_ibis: See Zynq PS DDR IBIS Decoder 

DDR Configuration Settings

DDR4

• DRAM Settings

  • Output Driver Impedance MR1 [2:1]

  • R_TT(nom) MR1 [10:8]

  • Dynamic ODT R_TT(wr) MR2 [11:9]

  • R_TT(park) MR5 [8:6]

• V_REF Calibration

  • DRAM V_REF_DQ (Writes)

    • Each byte is independently trained

    • The algorithm searches through one V_REF_DQ range between 60% and 90% of Vddq and will pick the center value of the observed valid range

  • DRAM V_REF_DQ (Reads)

    • Each byte is independently trained

    • The algorithm only searches through one V_REF_DQ range between 45.78% and 91.89% of Vcco and will pick the center value of the observed valid range

LPDDR4

• DRAM Settings

  • Drive Strength: MR3[5:3]

  • CA ODT: MR11[6:4]

  • DQ ODT: MR11[2:0]

  • V_REF CA Range: MR12[6:0]: JESD209-4, Table 12

  • V_REF DQ: MR14[5:0]: JESD209-4, Table 13

  • SOC ODT: MR22[2:0]

• V_REF Calibration

  • V_REF_CA fixed at 30.8%

  • DRAM V_REF_DQ (Writes)

    • Both channels share the same value

    • The V_REF training algorithm searches for the optimal V_REF_DQ between 10% and 30% Vddq and will pick the center value. Likely most designs will pass for this entire range and use a value of 20%

  • PS DDR V_REF_DQ (Reads)

    • Each channel can have an independent value

    • The V_REF training algorithm searches from 7.73% to 53.82% of Vcco and will find the center of the observed valid range

DDR3/3L

• DRAM Settings

  • Output Drive Strength, MR1[5,1]

  • R_TT(nom), MR1 [9,6,2]

  • R_TT(wr), MR2[10:9]

LPDDR3 Configuration Settings

• DRAM Settings

  • Drive Strength: MR3[3:0]

  • DQ ODT: MR11[1:0]

IBIS Models

Xilinx provides I/O Buffer Information Specification (IBIS) models for all supported I/O standards in FPGA and MPSoC devices.  This chapter provides guides on how to obtain custom and generic IBIS models. To aid in reviewing the IBIS models, name decoders have been included for both PL and PS models.

Generic and Custom IBIS models can be obtained or generated through the following methods. 

1. Generic IBIS models from Xilinx.com

2. Generate a custom IBIS model for PL designs

   1. Generate a custom PL IBIS File from the I/O Pin Planner

   2. Creating a Custom IBIS File from an Implemented Design

3. Generate a custom IBIS model for the Zynq MPSoC PS DDR

DDR specific IBIS model name decoders have been included for PL and PS models.

1. PL I/O Standards

2. PS DDR I/O Standards  

These represent a subset of the IBIS models provided by Xilinx.  For a complete IBIS decoding guide, please see the blog post “Xilinx PL and PS IBIS Model Decoders”

Generic IBIS Models from Xilinx.com

The generic IBIS model file contains models for all IO Standards supported by the selected family.  The generic IBIS model is package and die size agnostic.  A global RLC package model is set for every available IO.  The generic IBIS model contains every available IO model with no specific pin assignments.  The generic models are recommended for a small number of signals in a schematic level simulation.  It is not recommended to use the generic models for board level simulations.

Figure 1: Capture of available UltraScale+ IBIS Models from Xilinx.com

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Generic IBIS models can be found here

Vivado Generated, Custom IBIS Models

The Vivado generated, custom IBIS models are device, package and design specific.  The Vivado generated IBIS models can be used for Board Level and Schematic Level simulations.  The custom IBIS models include RLC package details for each individual package pin.

When generating a Custom IBIS model with a DDR IP (PL or PS) you must use the default IO settings like slew, equalization, ODT and drive strength.  These parameters are set by the memory configuration (FPGA, DRAM Type and Topology).  This information is summarized in the PL Controller and PS Controller Drive Strength, ODT and V_REF Configurations.

How to generate custom IBIS Files from Vivado

The following guides can be used to create custom PL or PS IBIS file(s) from within Vivado:

• Creating a Custom PL IBIS File from the I/O Pin Planner

• Creating a Custom PL IBIS File from an Implemented Design

• Creating a Custom IBIS File for Zynq PS DDR

Generate a custom PL IBIS File from the I/O Pin Planner

Creating an IBIS file from the I/O Pin Planner is useful for performing signal integrity simulations even if full Vivado design is not yet available.  If the pin-out of the Xilinx device is known, along with the required I/O standards and parameters, a custom IBIS file can be created.

The procedure is as follows:

• Open Vivado and double-click “Create New Project” (Figure 2)

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• On the “Create a New Vivado Project” window (Figure 3), click Next:

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• Enter a project name and directory (Figure 4), then click Next:

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• Choose “I/O Planning Project” (Figure 5), then click Next:

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• If you already have a CSV (or XDC file) that defines the pins and I/O standards, you can link to it now, or wait until later. For this document, we will import a CSV file at a later stage.

  • Choose “Do not import I/O ports at this time” (Figure 6) and click Next:

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• Choose the relevant Xilinx Part (Figure 7) and click Next:

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• New Project Summary (Figure 8) Click Finish:

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• When the project is created, a device view will be shown (Figure 9):

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• At this point, we are ready to begin the process of importing the ports from a CSV file. There is a way to manually create ports using the “Create I/O Ports” option, but this process takes longer and will not be covered at this time. Instead, it is recommended to import a CSV file containing the port definitions.

• Before importing the CSV file, it must be created.

• The CSV file has a particular format that is explained in greater detail in UG899: Vivado Design Suite User Guide, I/O and Clock Planning, though an example is shown below that pertains to a DDR4 memory design.

Example CSV File

• Figure 10 shows a complete CSV file that contains the relevant column headers, and examples of values that are suited for a DDR4 memory design containing 64 data bits (with Data Masks). Columns H, and I are used for differential signals such as clocks and DQS strobes.

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• Once the CSV file has been created, it can be imported into Vivado.  

  • Click on “Import I/O Ports” (Figure 11):

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• Import I/O Ports (Figure 12) Select “CSV File” and provide the path to the file, then Click OK:

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• The file will import, and package pins can be seen via the “I/O Ports” tab (Figure 13).

  • Any errors or warnings will be listed in the “Tcl Console” tab:

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• Now, the IBIS file can be exported (Figure 14).

  • Choose File->Export->Export IBIS Model

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• Export IBIS Model (Figure 15)

  • Choose an output file name and location (or keep default)

  • Keep “Include all models” UNCHECKED to keep the file size small 

  • Keep “Disable per pin modeling” UNCHECKED: This will combine the package data with the IBIS models

  • Choose a Component Name, not required.  For this example, it has been left blank.

  • Click OK to export the file

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• The IBIS file is now ready for use in simulation.

Creating a Custom PL IBIS File from an Implemented Design

The procedure for creating a custom IBIS file from an implemented design is very straight-forward, as all pin assignments have been completed as part of the design implementation.

• Begin by opening the project and then click “Open Implemented Design” (Figure 16)

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• Choose File->Export->Export IBIS Model

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• Export IBIS Model (Figure 18)

  • Choose an output file name and location (or keep default)

  • Keep “Include all models” UNCHECKED to keep the file size small 

  • Keep “Disable per pin modeling” UNCHECKED: This will combine the package data with the IBIS models

  • Choose a Component Name, not required.  This example calls out the FPGA device.

  • Click OK to export the file

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• The IBIS file is now ready for use in simulation.

How to Generate Custom IBIS File for Zynq PS DDR

To generate a custom IBIS file for the Zynq PS DDR launch a new RTL Project in Vivado. 

• Select the target Zynq device and package.

• When the new project is ready, create a block design in the IP Integrator (Figure 19)

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• Click on the “+” button to add IP, in the IP selector window, select “Zynq UltraScale+ MPSoC”

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• The zynq_ultra_ps_e_0 will be added to the diagram window

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• Double click on the Zynq block to open the Re-customize IP window (Figure 22).  Within the Re-customize IP window select “DDR Configuration” in the Page Navigator.  Select the appropriate DDR technology, Bus width, and ECC option.  It is not necessary to select anything else for the IBIS model.  In the example below the speed, bin has been updated to DDR4 2400P.

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• If needed, “Other options” can be expanded so “Parity” can be selected.

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• Click ok, the IP will be updated.  Right-click on the Zynq IP block, select “Make External.” 

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• Vivado will automatically add external signals (Figure 25)

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• To avoid receiving a warning about an un-assigned address click on the “Address Editor” tab (Figure 26) and select “Auto Assign Address”

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• In the Hierarchy window, click on the “Sources” tab.  Right-click on the design and select “Create HDL Wrapper” (Figure 27)

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• Select “Let Vivado manage wrapper and auto-update,” (Figure 28) press OK.

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• When the wrapper is complete select “Open Elaborated Design” (Figure 29) in the Flow Navigator. 

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• A dialog box will open with details about the Elaborated design (Figure 30).  Press OK.

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• When the Elaborated Design is open, Select File à Export à Export IBIS Model (Figure 31).

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• The Export IBIS Model window will open (Figure 32).  Set the output path, ensure “Include all models” and “Disable per pin modeling” boxes are not selected.  Component name can be assigned, but not necessary.

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• The custom PS IBIS file will now be generated.

Xilinx PL IBIS Decoder

The PL IBIS Decoder (Table 23) can be used to decode PL IBIS models for all PL I/Os.  This applies to the Zynq MPSoC PL I/Os.

Table 23: PL IBIS Decoder

All models (except for LVDS*) will contain Bank Type, IOStandard, Slew Rate and Output Impedance/Drive Strength.

• LVDS models will contain Bank Type, LVDS IOStandard and Digital Termination. 

Internal 100-ohm Differential Termination is only available in banks powered at 1.8V (LVDS) or 2.5V (LVDS_25).  See (UG571), v1.12, p.130 for more details.

Note: not all model settings will be present in every IBIS model.  If a setting is not in the model name, that setting is not supported by the model.

Table 24 provides an example of the PL DDR4 IBIS Models.

Table 24: PL DDR4 IBIS Models

Xilinx Zynq PS DDR IBIS Decoder

The Zynq MPSoC PS DDR IBIS signals are unique from all other signals.

Table 25 is a decoder for the Zynq MPSoC PS DDR IBIS models. 

Examples of each DDR memory type IBIS model are provided in Tables 26 through 30

Table 25: Zynq PS DDR IBIS Decoder

Zynq PS DDR IBIS Examples

Table 26: PS DDR4

Table 27: PS LPDDR4

Table 28: PS DDR3

Table 29: PS DDR3L

Table 30: PS LPDDR3

Available Resources for HyperLynx and ADS Simulation Tools

Xilinx provides the following resources to aid in performing DDR interface simulations. The UltraScale+ content is available through the UltraScale+ Signal and Power Integrity Lounge or upon request.  Please submit requests through your FAE.

UltraScale+

UltraScale+ Signal and Power Integrity Lounge

• DDR4 ADS Simulation Kit

• HyperLynx DDRx Timing models

  • The PL timing models are applicable for all devices across Virtex UltraScale+, Kintex UltraScale+ and Zynq UltraScale+ families

    • PL DDR4 @ 2667Mbps

    • PL DDR3L @ 1866Mbps

  • The PS models are only applicable for the Zynq UltraScale+ family

    • PS DDR4 @ 2400Mbps

    • PS LPDDR4 @ 2400Mbps

    • PS DDR3L @ 1866Mbps

HyperLynx DDRx Tips

This section provides some tips on how to properly setup the HyperLynx DDRx wizard.  This is not a comprehensive guide on how to use the DDRx wizard. 

ODT Models

ODT Models need to be set in the DDRx Wizard.  Use the appropriate impedance and ODT values for the PL or PS Controller and DDR type.  The capture below is the setup for the Xilinx ZCU104, 64-bit component DDR4 interface.

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Leveling and Calibration

The PL and PS DDR controllers support the leveling and calibration settings in the capture below.  It is recommended to select “Automatically run simulation 2 times: to estimate skews and to apply them”

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Timing Models

For the most accurate DDRx simulation, it is recommended to use the Xilinx timing models. 

• The Xilinx timing model numbers will need to be entered using the “TM Wizard”

• In the capture below, the TM Wizard was used to create “PS_DDR4_2400Mbps_DDRx.v”

If Xilinx timing models for the target data rate are not available, two options

• Use Xilinx timing models for the closest available data rate and simulate at that data rate

• Use the generic timing HyperLynx DDRx timing model for your target data rate      

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V_REF Training

For PL DDR4, PS DDR4 and PS LPDDR4 select “Single V_REF for all the signals”. 

• PL DDR4 V_REF is fixed: For details on the PL DDR4 V_REF see PL Controller ODT/V_REF Configuration, DDR Configuration Settings for DDR4

• PS DDR4 and PS LPDDR4 V_REF is calibrated: For details on the PS DDR4 and PS LPDDR4 V_REF see PS Controller ODT/V_REF Configuration, DDR Configuration Settings for DDR4 and LPDDR4.

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Simulation Options

Set desired IC model corners.  In HyperLynx version 2.4 and newer, the measurement location can be set on the Simulation options page.  

• The DRAM specs call for timing analysis to be performed at the pin of the DRAM

• The FPGA has relatively long package signal lengths, thus probing should be done at the die of the FPGA

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Figure 38 shows an example of probing at the Zynq pin vs Zynq die on ZCU104, PS DDR4, DQ4

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If using a HyperLynx version before v2.4, the Xilinx Custom IBIS model will need to be modified to indicate the timing location.  If no timing location is in the IBIS model, timing will be performed at the pin.

• Mentor KB Article ID# MG83246: HyperLynx SI: Probing at the Die for Batch and Interactive Simulations

• Virtex UltraScale Plus IBIS example (Figure 39)

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