External Memory Interface Handbook Volume 2: Design Guidelines: For UniPHY-based Device Families

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ID 683385
Date 3/06/2023
Public
Document Table of Contents
Document Table of Contents x
1. Planning Pin and FPGA Resources 2. DDR2 and DDR3 SDRAM Board Design Guidelines 3. Dual-DIMM DDR2 and DDR3 SDRAM Board Design Guidelines 4. LPDDR2 SDRAM Board Design Guidelines 5. RLDRAM II and RLDRAM 3 Board Design Guidelines 6. QDR II/II+ SRAM Board Design Guidelines 7. Implementing and Parameterizing Memory IP 8. Simulating Memory IP 9. Analyzing Timing of Memory IP 10. Debugging Memory IP 11. Optimizing the Controller 12. PHY Considerations 13. Power Estimation Methods for External Memory Interfaces
1. Planning Pin and FPGA Resources x
1.1. Interface Pins 1.2. Guidelines for UniPHY-based External Memory Interface IP 1.3. Using PLL Guidelines 1.4. PLL Cascading 1.5. DLL 1.6. Other FPGA Resources 1.7. Document Revision History
1.1. Interface Pins x
1.1.1. Estimating Pin Requirements 1.1.2. DDR, DDR2, and DDR3 SDRAM Clock Signals 1.1.3. DDR, DDR2, and DDR3 SDRAM Command and Address Signals 1.1.4. DDR, DDR2, and DDR3 SDRAM Data, Data Strobes, DM/DBI, and Optional ECC Signals 1.1.5. DDR, DDR2, and DDR3 SDRAM DIMM Options 1.1.6. QDR II and QDR II+ SRAM Clock Signals 1.1.7. QDR II and QDR II+ SRAM Command Signals 1.1.8. QDR II and QDR II+ SRAM Address Signals 1.1.9. QDR II and QDR II+ SRAM Data, BWS, and QVLD Signals 1.1.10. RLDRAM II and RLDRAM 3 Clock Signals 1.1.11. RLDRAM II and RLDRAM 3 Commands and Addresses 1.1.12. RLDRAM II and RLDRAM 3 Data, DM and QVLD Signals 1.1.13. LPDDR2 Clock Signal 1.1.14. LPDDR2 Command and Address Signal 1.1.15. LPDDR2 Data, Data Strobe, and DM Signals 1.1.16. Maximum Number of Interfaces 1.1.17. OCT Support
1.1.16. Maximum Number of Interfaces x
1.1.16.1. Maximum Number of DDR SDRAM Interfaces Supported per FPGA 1.1.16.2. Maximum Number of DDR2 SDRAM Interfaces Supported per FPGA 1.1.16.3. Maximum Number of DDR3 SDRAM Interfaces Supported per FPGA 1.1.16.4. Maximum Number of QDR II and QDR II+ SRAM Interfaces Supported per FPGA 1.1.16.5. Maximum Number of RLDRAM II Interfaces Supported per FPGA 1.1.16.6. Maximum Number of LPDDR2 SDRAM Interfaces Supported per FPGA
1.2. Guidelines for UniPHY-based External Memory Interface IP x
1.2.1. General Pin-out Guidelines for UniPHY-based External Memory Interface IP 1.2.2. Pin-out Rule Exceptions for ×36 Emulated QDR II and QDR II+ SRAM Interfaces in Arria II, Stratix III and Stratix IV Devices 1.2.3. Pin-out Rule Exceptions for RLDRAM II and RLDRAM 3 Interfaces 1.2.4. Pin-out Rule Exceptions for QDR II and QDR II+ SRAM Burst-length-of-two Interfaces 1.2.5. Pin Connection Guidelines Tables 1.2.6. PLLs and Clock Networks
1.2.2. Pin-out Rule Exceptions for ×36 Emulated QDR II and QDR II+ SRAM Interfaces in Arria II, Stratix III and Stratix IV Devices x
1.2.2.1. Timing Impact on x36 Emulation 1.2.2.2. Rules to Combine Groups 1.2.2.3. Determining the CQ/CQn Arrival Time Skew
1.2.3. Pin-out Rule Exceptions for RLDRAM II and RLDRAM 3 Interfaces x
1.2.3.1. Interfacing with ×9 RLDRAM II CIO Devices 1.2.3.2. Interfacing with ×18 RLDRAM II and RLDRAM 3 CIO Devices 1.2.3.3. Interfacing with RLDRAM II and RLDRAM 3 ×36 CIO Devices
1.2.5. Pin Connection Guidelines Tables x
1.2.5.1. DDR3 SDRAM With Leveling Interface Pin Utilization Applicable for Arria V GZ, Stratix III, Stratix IV, and Stratix V Devices 1.2.5.2. QDR II and QDR II+ SRAM Pin Utilization for Arria II, Arria V, Stratix III, Stratix IV, and Stratix V Devices 1.2.5.3. RLDRAM II CIO Pin Utilization for Arria II GZ, Arria V, Stratix III, Stratix IV, and Stratix V Devices  1.2.5.4. LPDDR2 Pin Utilization for Arria V, Cyclone V, and MAX 10 FPGA Devices 1.2.5.5. Additional Guidelines for Arria V GZ and Stratix V Devices 1.2.5.6. Additional Guidelines for Arria V ( Except Arria V GZ) Devices 1.2.5.7. Additional Guidelines for MAX 10 Devices 1.2.5.8. Additional Guidelines for Cyclone V Devices
1.2.6. PLLs and Clock Networks x
1.2.6.1. Number of PLLs Available in Intel® Device Families 1.2.6.2. Number of Enhanced PLL Clock Outputs and Dedicated Clock Outputs Available in Intel® Device Families 1.2.6.3. Number of Clock Networks Available in Intel® Device Families 1.2.6.4. Clock Network Usage in UniPHY-based Memory Interfaces—DDR2 and DDR3 SDRAM (1) (2) 1.2.6.5. Clock Network Usage in UniPHY-based Memory Interfaces—RLDRAM II, and QDR II and QDR II+ SRAM 1.2.6.6. PLL Usage for DDR, DDR2, and DDR3 SDRAM Without Leveling Interfaces 1.2.6.7. PLL Usage for DDR3 SDRAM With Leveling Interfaces
2. DDR2 and DDR3 SDRAM Board Design Guidelines x
2.1. Leveling and Dynamic Termination 2.2. DDR2 Terminations and Guidelines 2.3. DDR3 Terminations in Arria V, Cyclone V, Stratix III, Stratix IV, and Stratix V 2.4. Layout Approach 2.5. Channel Signal Integrity Measurement 2.6. Design Layout Guidelines 2.7. Package Deskew 2.8. Document Revision History
2.1. Leveling and Dynamic Termination x
2.1.1. Read and Write Leveling 2.1.2. Dynamic ODT 2.1.3. Dynamic On-Chip Termination 2.1.4. Dynamic On-Chip Termination in Stratix III and Stratix IV Devices 2.1.5. Dynamic OCT in Stratix V Devices
2.1.3. Dynamic On-Chip Termination x
2.1.3.1. FPGA Writing to Memory 2.1.3.2. FPGA Reading from Memory
2.2. DDR2 Terminations and Guidelines x
2.2.1. Termination for DDR2 SDRAM 2.2.2. DDR2 Design Layout Guidelines 2.2.3. General Layout Guidelines 2.2.4. Layout Guidelines for DDR2 SDRAM Interface
2.2.1. Termination for DDR2 SDRAM x
2.2.1.1. External Parallel Termination 2.2.1.2. On-Chip Termination 2.2.1.3. Recommended Termination Schemes
2.3. DDR3 Terminations in Arria V, Cyclone V, Stratix III, Stratix IV, and Stratix V x
2.3.1. Terminations for Single-Rank DDR3 SDRAM Unbuffered DIMM 2.3.2. Terminations for Multi-Rank DDR3 SDRAM Unbuffered DIMM 2.3.3. Terminations for DDR3 SDRAM Registered DIMM 2.3.4. Terminations for DDR3 SDRAM Load-Reduced DIMM 2.3.5. Terminations for DDR3 SDRAM Components With Leveling
2.3.5. Terminations for DDR3 SDRAM Components With Leveling x
2.3.5.1. DDR3 SDRAM Components With or Without Leveling
2.5. Channel Signal Integrity Measurement x
2.5.1. Importance of Accurate Channel Signal Integrity Information 2.5.2. Understanding Channel Signal Integrity Measurement 2.5.3. How to Enter Calculated Channel Signal Integrity Values 2.5.4. Guidelines for Calculating DDR3 Channel Signal Integrity
2.6. Design Layout Guidelines x
2.6.1. General Layout Guidelines 2.6.2. Layout Guidelines for DDR3 SDRAM Interfaces 2.6.3. Length Matching Rules 2.6.4. Spacing Guidelines 2.6.5. Layout Guidelines for DDR3 SDRAM Wide Interface (>72 bits)
2.6.5. Layout Guidelines for DDR3 SDRAM Wide Interface (>72 bits) x
2.6.5.1. Fly-By Network Design for Clock, Command, and Address Signals
2.7. Package Deskew x
2.7.1. Package Deskew Recommendation for Stratix V Devices 2.7.2. DQ/DQS/DM Deskew 2.7.3. Address and Command Deskew 2.7.4. Deskew Example 2.7.5. Package Migration 2.7.6. Package Deskew for RLDRAM II and RLDRAM 3
3. Dual-DIMM DDR2 and DDR3 SDRAM Board Design Guidelines x
3.1. General Layout Guidelines 3.2. Dual-Slot Unbuffered DDR2 SDRAM 3.3. Dual-Slot Unbuffered DDR3 SDRAM 3.4. Document Revision History
3.2. Dual-Slot Unbuffered DDR2 SDRAM x
3.2.1. Overview of ODT Control 3.2.2. DIMM Configuration 3.2.3. Dual-DIMM Memory Interface with Slot 1 Populated 3.2.4. Dual-DIMM with Slot 2 Populated 3.2.5. Dual-DIMM Memory Interface with Both Slot 1 and Slot 2 Populated 3.2.6. Dual-DIMM DDR2 Clock, Address, and Command Termination and Topology 3.2.7. Control Group Signals 3.2.8. Clock Group Signals
3.2.3. Dual-DIMM Memory Interface with Slot 1 Populated x
3.2.3.1. FPGA Writing to Memory 3.2.3.2. Write to Memory Using an ODT Setting of 150-ohm 3.2.3.3. Reading from Memory
3.2.4. Dual-DIMM with Slot 2 Populated x
3.2.4.1. FPGA Writing to Memory 3.2.4.2. Write to Memory Using an ODT Setting of 150-ohm 3.2.4.3. Reading from Memory
3.2.5. Dual-DIMM Memory Interface with Both Slot 1 and Slot 2 Populated x
3.2.5.1. FPGA Writing to Memory 3.2.5.2. Write to Memory in Slot 1 Using an ODT Setting of 75-ohm 3.2.5.3. Reading From Memory
3.3. Dual-Slot Unbuffered DDR3 SDRAM x
3.3.1. Comparison of DDR3 and DDR2 DQ and DQS ODT Features and Topology 3.3.2. Dual-DIMM DDR3 Clock, Address, and Command Termination and Topology 3.3.3. FPGA OCT Features
3.3.2. Dual-DIMM DDR3 Clock, Address, and Command Termination and Topology x
3.3.2.1. Address and Command Signals 3.3.2.2. Control Group Signals 3.3.2.3. Clock Group Signals
3.3.3. FPGA OCT Features x
3.3.3.1. Arria V, Cyclone V, Stratix III, Stratix IV, and Stratix V Devices 3.3.3.2. Arria II GX Devices
4. LPDDR2 SDRAM Board Design Guidelines x
4.1. LPDDR2 Guidance 4.2. Document Revision History
4.1. LPDDR2 Guidance x
4.1.1. LPDDR2 SDRAM Configurations 4.1.2. OCT Signal Terminations for Arria V and Cyclone V Devices 4.1.3. General Layout Guidelines 4.1.4. LPDDR2 Layout Guidelines
4.1.2. OCT Signal Terminations for Arria V and Cyclone V Devices x
4.1.2.1. Outputs from the FPGA to the LPDDR2 Component 4.1.2.2. Input to the FPGA from the LPDDR2 SDRAM Component 4.1.2.3. Termination Schemes
5. RLDRAM II and RLDRAM 3 Board Design Guidelines x
5.1. RLDRAM II Configurations 5.2. RLDRAM 3 Configurations 5.3. Signal Terminations 5.4. PCB Layout Guidelines 5.5. General Layout Guidelines 5.6. RLDRAM II and RLDRAM 3 Layout Guidelines 5.7. Layout Approach 5.8. Package Deskew for RLDRAM II and RLDRAM 3 5.9. Document Revision History
5.3. Signal Terminations x
5.3.1. Input to the FPGA from the RLDRAM Components 5.3.2. Outputs from the FPGA to the RLDRAM II and RLDRAM 3 Components 5.3.3. RLDRAM II Termination Schemes 5.3.4. RLDRAM 3 Termination Schemes
5.7. Layout Approach x
5.7.1. Arria V and Stratix V Board Setting Parameters
6. QDR II/II+ SRAM Board Design Guidelines x
6.1. QDR II SRAM Configurations 6.2. Signal Terminations 6.3. General Layout Guidelines 6.4. QDR II Layout Guidelines 6.5. QDR II SRAM Layout Approach 6.6. Package Deskew for QDR II 6.7. Document Revision History
6.2. Signal Terminations x
6.2.1. Output from the FPGA to the QDR II SRAM Component 6.2.2. Input to the FPGA from the QDR II SRAM Component 6.2.3. Termination Schemes
7. Implementing and Parameterizing Memory IP x
7.1. Design Flow 7.2. UniPHY-Based External Memory Interface IP 7.3. Document Revision History
7.1. Design Flow x
7.1.1. IP Catalog Design Flow 7.1.2. Platform Designer System Integration Tool Design Flow
7.1.1. IP Catalog Design Flow x
7.1.1.1. IP Catalog and Parameter Editor 7.1.1.2. Specifying Parameters for the IP Catalog Flow 7.1.1.3. Using Example Designs 7.1.1.4. Constraining the Design 7.1.1.5. Compiling the Design
7.1.1.4. Constraining the Design x
7.1.1.4.1. Adding Pins and DQ Group Assignments
7.1.2. Platform Designer System Integration Tool Design Flow x
7.1.2.1. Specify Parameters for the Platform Designer Flow 7.1.2.2. Completing the Platform Designer System
7.2. UniPHY-Based External Memory Interface IP x
7.2.1. Platform Designer Interfaces 7.2.2. Generated Files for Memory Controllers with the UniPHY IP 7.2.3. Parameterizing Memory Controllers 7.2.4. Board Settings 7.2.5. Controller Settings for UniPHY IP 7.2.6. Diagnostics for UniPHY IP
7.2.1. Platform Designer Interfaces x
7.2.1.1. DDR2 SDRAM Controller with UniPHY Intel FPGA IP Interfaces 7.2.1.2. DDR3 SDRAM Controller with UniPHY Intel FPGA IP Interfaces 7.2.1.3. LPDDR2 SDRAM Controller with UniPHY Intel FPGA IP Interfaces 7.2.1.4. QDR II and QDR II+ SRAM Controller with UniPHY Intel FPGA IP Interfaces 7.2.1.5. RLDRAM II Controller with UniPHY Intel FPGA IP Interfaces 7.2.1.6. RLDRAM 3 UniPHY Intel FPGA IP Interface
7.2.3. Parameterizing Memory Controllers x
7.2.3.1. PHY Settings for UniPHY IP 7.2.3.2. Memory Parameters for LPDDR2, DDR2 and DDR3 SDRAM Controller with UniPHY Intel FPGA IP 7.2.3.3. Memory Parameters for QDR II and QDR II+ SRAM Controller with UniPHY Intel FPGA IP 7.2.3.4. Memory Parameters for RLDRAM II Controller with UniPHY Intel FPGA IP 7.2.3.5. Memory Timing Parameters for DDR2, DDR3, and LPDDR2 SDRAM Controller with UniPHY Intel FPGA IP 7.2.3.6. Memory Timing Parameters for QDR II and QDR II+ SRAM Controller with UniPHY Intel FPGA IP 7.2.3.7. Memory Timing Parameters for RLDRAM II Controller with UniPHY Intel FPGA IP 7.2.3.8. Memory Parameters for RLDRAM 3 UniPHY Intel FPGA IP
7.2.3.2. Memory Parameters for LPDDR2, DDR2 and DDR3 SDRAM Controller with UniPHY Intel FPGA IP x
7.2.3.2.1. Memory Initialization Options for DDR2 7.2.3.2.2. Memory Initialization Options for DDR3 7.2.3.2.3. Memory Initialization Options for LPDDR2
7.2.4. Board Settings x
7.2.4.1. Setup and Hold Derating for UniPHY IP 7.2.4.2. Intersymbol Interference Channel Signal Integrity for UniPHY IP 7.2.4.3. Board Skews for UniPHY IP
7.2.4.3. Board Skews for UniPHY IP x
7.2.4.3.1. Board Skew Parameters for LPDDR2/DDR2/DDR3 SDRAM 7.2.4.3.2. Board Skew Parameters for QDR II and QDR II+ 7.2.4.3.3. Board Skew parameters for RLDRAM II and RLDRAM 3
8. Simulating Memory IP x
8.1. Simulation Options 8.2. Simulation Walkthrough with UniPHY IP 8.3. Document Revision History
8.2. Simulation Walkthrough with UniPHY IP x
8.2.1. Simulation Scripts 8.2.2. Preparing the Vendor Memory Model 8.2.3. Functional Simulation with Verilog HDL 8.2.4. Functional Simulation with VHDL 8.2.5. Simulating the Example Design 8.2.6. UniPHY Abstract PHY Simulation 8.2.7. PHY-Only Simulation 8.2.8. Post-fit Functional Simulation 8.2.9. Simulation Issues
8.2.8. Post-fit Functional Simulation x
8.2.8.1. Running Post-fit Simulation
9. Analyzing Timing of Memory IP x
9.1. Memory Interface Timing Components 9.2. FPGA Timing Paths 9.3. Timing Constraint and Report Files for UniPHY IP 9.4. Timing Analysis Description 9.5. Timing Report DDR 9.6. Report SDC 9.7. Calibration Effect in Timing Analysis 9.8. Timing Model Assumptions and Design Rules 9.9. Common Timing Closure Issues 9.10. Optimizing Timing 9.11. Timing Deration Methodology for Multiple Chip Select DDR2 and DDR3 SDRAM Designs 9.12. Performing I/O Timing Analysis 9.13. Document Revision History
9.1. Memory Interface Timing Components x
9.1.1. Source-Synchronous Paths 9.1.2. Calibrated Paths 9.1.3. Internal FPGA Timing Paths 9.1.4. Other FPGA Timing Parameters
9.2. FPGA Timing Paths x
9.2.1. Arria II Device PHY Timing Paths 9.2.2. Stratix III and Stratix IV PHY Timing Paths 9.2.3. Arria V, Arria V GZ, Cyclone V, and Stratix V Timing paths
9.4. Timing Analysis Description x
9.4.1. UniPHY IP Timing Analysis
9.4.1. UniPHY IP Timing Analysis x
9.4.1.1. Address and Command 9.4.1.2. PHY or Core 9.4.1.3. PHY or Core Reset 9.4.1.4. Read Capture and Write 9.4.1.5. Read Resynchronization 9.4.1.6. DQS versus CK—Arria II GX and Cyclone IV Devices 9.4.1.7. Write Leveling tDQSS 9.4.1.8. Write Leveling tDSH/tDSS 9.4.1.9. DK versus CK (RLDRAM II with UniPHY) 9.4.1.10. Bus Turnaround Time
9.4.1.4. Read Capture and Write x
9.4.1.4.1. Stratix III 9.4.1.4.2. Arria II, Arria V, Cyclone V, Stratix IV and Stratix V
9.7. Calibration Effect in Timing Analysis x
9.7.1. Calibration Emulation for Calibrated Path 9.7.2. Calibration Error or Quantization Error 9.7.3. Calibration Uncertainties 9.7.4. Memory Calibration
9.8. Timing Model Assumptions and Design Rules x
9.8.1. Memory Clock Output Assumptions 9.8.2. Write Data Assumptions 9.8.3. Read Data Assumptions 9.8.4. DLL Assumptions 9.8.5. PLL and Clock Network Assumptions for Stratix III Devices
9.8.1. Memory Clock Output Assumptions x
9.8.1.1. Memory Clock Assumptions for Stratix III Devices
9.8.2. Write Data Assumptions x
9.8.2.1. Write Data Assumptions for Stratix III Devices
9.8.3. Read Data Assumptions x
9.8.3.1. Read Data Assumptions for Stratix III Devices
9.9. Common Timing Closure Issues x
9.9.1. Missing Timing Margin Report 9.9.2. Incomplete Timing Margin Report 9.9.3. Read Capture Timing 9.9.4. Write Timing 9.9.5. Address and Command Timing 9.9.6. PHY Reset Recovery and Removal 9.9.7. Clock-to-Strobe (for DDR and DDR2 SDRAM Only) 9.9.8. Read Resynchronization and Write Leveling Timing (for SDRAM Only)
9.11. Timing Deration Methodology for Multiple Chip Select DDR2 and DDR3 SDRAM Designs x
9.11.1. Multiple Chip Select Configuration Effects 9.11.2. Timing Deration using the Board Settings
9.11.1. Multiple Chip Select Configuration Effects x
9.11.1.1. ISI Effects 9.11.1.2. Calibration Effects 9.11.1.3. Board Effects
9.11.2. Timing Deration using the Board Settings x
9.11.2.1. Slew Rates 9.11.2.2. Slew Rate Setup, Hold, and Derating Calculation 9.11.2.3. Intersymbol Interference 9.11.2.4. Measuring Eye Reduction for Address/Command, DQ, and DQS Setup and Hold Time
9.12. Performing I/O Timing Analysis x
9.12.1. Performing I/O Timing Analysis with Third-Party Simulation Tools 9.12.2. Performing Advanced I/O Timing Analysis with Board Trace Delay Model
10. Debugging Memory IP x
10.1. Resource and Planning Issues 10.2. Interface Configuration Performance Issues 10.3. Functional Issue Evaluation 10.4. Timing Issue Characteristics 10.5. Verifying Memory IP Using the Signal Tap II Logic Analyzer 10.6. Hardware Debugging Guidelines 10.7. Categorizing Hardware Issues 10.8. EMIF Debug Toolkit Overview 10.9. Document Revision History
10.1. Resource and Planning Issues x
10.1.1. Dedicated DLL Resources 10.1.2. Dedicated IOE DQS Group Resources and Pins 10.1.3. Specific PLL Resources 10.1.4. Specific Global, Regional and Dual-Regional Clock Net Resources 10.1.5. Planning Your Design 10.1.6. Optimizing Design Utilization
10.2. Interface Configuration Performance Issues x
10.2.1. Interface Configuration Bottleneck and Efficiency Issues
10.3. Functional Issue Evaluation x
10.3.1. Correct Combination of the Quartus Prime Software and ModelSim* - Intel® FPGA Edition Device Models 10.3.2. Intel® IP Memory Model 10.3.3. Vendor Memory Model 10.3.4. Insufficient Memory in Your PC 10.3.5. Transcript Window Messages 10.3.6. Passing Simulation 10.3.7. Modifying the Example Driver to Replicate the Failure
10.4. Timing Issue Characteristics x
10.4.1. Evaluating FPGA Timing Issues 10.4.2. Evaluating External Memory Interface Timing Issues
10.5. Verifying Memory IP Using the Signal Tap II Logic Analyzer x
10.5.1. Signals to Monitor with the Signal Tap II Logic Analyzer
10.6. Hardware Debugging Guidelines x
10.6.1. Create a Simplified Design that Demonstrates the Same Issue 10.6.2. Measure Power Distribution Network 10.6.3. Measure Signal Integrity and Setup and Hold Margin 10.6.4. Vary Voltage 10.6.5. Use Freezer Spray and Heat Gun 10.6.6. Operate at a Lower Speed 10.6.7. Determine Whether the Issue Exists in Previous Versions of Software 10.6.8. Determine Whether the Issue Exists in the Current Version of Software 10.6.9. Try A Different PCB 10.6.10. Try Other Configurations 10.6.11. Debugging Checklist
10.7. Categorizing Hardware Issues x
10.7.1. Signal Integrity Issues 10.7.2. Hardware and Calibration Issues
10.7.1. Signal Integrity Issues x
10.7.1.1. Characteristics of Signal Integrity Issues 10.7.1.2. Evaluating SignaI Integrity Issues
10.7.1.2. Evaluating SignaI Integrity Issues x
10.7.1.2.1. Skew 10.7.1.2.2. Crosstalk 10.7.1.2.3. Power System 10.7.1.2.4. Clock Signals 10.7.1.2.5. Read Data Valid Window and Eye Diagram 10.7.1.2.6. Write Data Valid Window and Eye Diagram 10.7.1.2.7. OCT and ODT Usage
10.7.2. Hardware and Calibration Issues x
10.7.2.1. Evaluating Hardware and Calibration Issues
10.7.2.1. Evaluating Hardware and Calibration Issues x
10.7.2.1.1. Write Timing Margin 10.7.2.1.2. Read Timing Margin 10.7.2.1.3. Address and Command Timing Margin 10.7.2.1.4. Resynchronization Timing Margin 10.7.2.1.5. Postamble Timing Issues and Margin 10.7.2.1.6. Intermittent Issue Evaluation
11. Optimizing the Controller x
11.1. Factors Affecting Efficiency 11.2. Ways to Improve Efficiency 11.3. Document Revision History
11.1. Factors Affecting Efficiency x
11.1.1. Interface Standard 11.1.2. Bank Management Efficiency 11.1.3. Data Transfer
11.2. Ways to Improve Efficiency x
11.2.1. DDR2 SDRAM Controller 11.2.2. Auto-Precharge Commands 11.2.3. Additive Latency 11.2.4. Bank Interleaving 11.2.5. Command Queue Look-Ahead Depth 11.2.6. Additive Latency and Bank Interleaving 11.2.7. User-Controlled Refresh 11.2.8. Frequency of Operation 11.2.9. Burst Length 11.2.10. Series of Reads or Writes 11.2.11. Data Reordering 11.2.12. Starvation Control 11.2.13. Command Reordering 11.2.14. Bandwidth 11.2.15. Efficiency Monitor
12. PHY Considerations x
12.1. Core Logic and User Interface Data Rate 12.2. Hard and Soft Memory PHY 12.3. Sequencer 12.4. PLL, DLL and OCT Resource Sharing 12.5. Pin Placement Consideration 12.6. Document Revision History
13. Power Estimation Methods for External Memory Interfaces x
13.1. Performing Vector-Based Power Analysis with the Power Analyzer 13.2. Document Revision History
1. Planning Pin and FPGA Resources
2. DDR2 and DDR3 SDRAM Board Design Guidelines
3. Dual-DIMM DDR2 and DDR3 SDRAM Board Design Guidelines
4. LPDDR2 SDRAM Board Design Guidelines
5. RLDRAM II and RLDRAM 3 Board Design Guidelines
6. QDR II/II+ SRAM Board Design Guidelines
7. Implementing and Parameterizing Memory IP
8. Simulating Memory IP
9. Analyzing Timing of Memory IP
10. Debugging Memory IP
11. Optimizing the Controller
12. PHY Considerations
13. Power Estimation Methods for External Memory Interfaces

11.2.2. Auto-Precharge Commands

The auto-precharge read and write commands allow you to indicate to the memory device that a given read or write command is the last access to the currently opened row.

The memory device automatically closes or auto-precharges the page that is currently being accessed, so that the next access to the same bank is faster. The Auto-Precharge command is useful when you want to perform fast random memory accesses.

The Timer Bank Pool (TBP) block supports the dynamic page policy, where depending on user input on local autoprecharge input would keep a page open or close. In a closed-page policy, a page is always closed after it is accessed with auto-precharge command. When the data pattern consists of repeated reads or writes to addresses not within the same page, the optimal system achieves the maximum efficiency allowed by continuous page miss limited access. Efficiency losses are limited to those associated with activating and refreshing. An efficiency of 10-20% should be expected for this closed-page policy.

In an open-page policy, the page remains open after it is accessed for incoming commands. When the data pattern consists of repeated reads or writes to sequential addresses within the same page, the optimal system can achieve 100% efficiency for page-open transactions (ignoring the effects of periodic refreshes, which typically consume around 2-3% of total efficiency), with minimum latency for highest priority single transactions.

If you turn on Enable Auto-Precharge Control, you can instruct the controller to issue an autoprecharge read or write command. The next time you access that bank, the access is faster because the controller does not have to precharge the bank before activating the row that you want to access.

The controller-derived autoprecharge logic evaluates the pending commands in the command buffer and determines the most efficient autoprecharge operation to perform. The autoprecharge logic can reorder commands if necessary. When all TBP are occupied due to tracking an open page, TBP uses a scheme called on-demand flush, where it stops tracking a page to create space for an incoming command.

The following figure compares auto-precharge with and without look-ahead support.

Figure 81. Comparison With and Without Look-ahead Auto-Precharge


Without using the look-ahead auto-precharge feature, the controller must precharge to close and then open the row before the write or read burst for every row change. When using the look-ahead precharge feature, the controller decides whether to do auto-precharge read/write by evaluating the incoming command; subsequent reads or writes to same bank/different row require only an activate command.

As shown in the preceding figure, the controller performs an auto-precharge for the write command to bank 0 at cycle 1. The controller detects that the next write at cycle 13 is to a different row in bank 0, and hence saves 2 data cycles.

The following efficiency results apply to the above figure:

Table 87.  Comparative Efficiencies With and Without Look-Ahead Auto-Precharge Feature

Without Look-ahead Auto-precharge

With Look-ahead Auto-precharge

Active cycles of data transfer

16

16

Total number of cycles

19

17

Approximate efficiency

84%

94%

The look-ahead auto-precharge used increases efficiency by approximately 10%.

The following figure shows how you can improve controller efficiency using the auto-precharge command.

Figure 82. Improving Efficiency Using Auto-Precharge Command


The following sequence of events describes the above figure:

  1. The controller accepts a read request from the local side as soon as the local_ready signal goes high.
  2. The controller gives the activate command and then gives the read command. The read command latency is approximately 14 clock cycles for this case as compared to the similar case with no auto precharge which had approximately 17 clock cycles of latency (described in the "data Transfer" topic).

When using the auto-precharge option, note the following guidelines:

  • Use the auto-precharge command if you know the controller is issuing the next read or write to a particular bank and a different row.
  • Auto-precharge does not improve efficiency if you auto-precharge a row and immediately reopen it.
Level Two Title